Catalogue inclusive of experimental manuals
Ultrasound Ultrasound for education and laboratory purposes
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GAMPT
Dear Customer, we are proud to present our ultrasound products and accessories for educational and training purposes. For your convenience we have combined some of our items into focussed experimental sets. Each set has been assembled for specific ultrasonic experiments and includes detailed learning and assessment materials for students and tutors. Our equipment, e.g. the A-Scan echoscope, is used worldwide and has been proven in universities and colleges for many years. Our products are continuously being developed and extended to offer new learning opportunities, like the acousto-optical modulation found in this catalogue. The purpose of our experiments is first to allow students to learn the basic principles of ultrasound technology and then to explore their applications in various fields such as medicine or industry. If you have a specific requirement which is not listed here, we would welcome your comments and suggestions as to how we can better meet your particular needs. We hope you enjoy browsing through our new catalogue. Sincerely yours
Dr. Michael Schultz Managing Director
Dr. Grit Oblonczek Marketing Manager
Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Content
Ultrasound in laboratory course Nowadays ultrasound has as wide range of applicational uses extending from household and medicine to many industrial areas. Some examples for applied uses of ultrasound are found in humidifiers, ultrasonic cleaning devices, distance measuring devices, inner organs and foetus sonography, analysis of blood flow, therapeutic ultrasonic devices, filling-level meters (level indicator), ultrasonic welding, echo-sounder and NDT (non destructive testing). A basic knowledge of generation, expansion and interaction of ultrasound, the principal construction of ultrasonic devices as well as special measuring principles for applied scientific and medical applications is useful and even necessary.
Content Experimental sets
4-13
Set 1 Basics of ultrasound
5
Set 2 Basics of ultrasound, medical applications
6
Set 3 Basics of ultrasound, applications for engineers and material science
7
Set 4 Advanced applications of ultrasound
8
Set 5 Debye- Sears effect
9
Set 6 Ultrasonic Doppler effect
10
Set 7 Ultrasonic Doppler effect in medicine (Doppler sonography)
11
Set 8 Acousto-optical effects
12
Set 9 Extension set - ultrasonic CT and scanning methods
13
Equipment / Material
14-33
Pulse echo ultrasonic methods
14-21
CW (continuous wave) methods
22-27
Ultrasonic Doppler methods
28-31
Ultrasonic scanning methods
32-33
Experiments
34-67
Physical applications (PHY01-20)
36-55
Industrial applications (IND01-08)
56-63
Medical applications (MED01-04)
64-67
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
Experimental sets
For our more popular ranges we have assembled a series of experimental sets which are shown on the following pages. Various experiments can be carried out with each set to demonstrate particular ultrasonic topics. All sets can be extended or combined with other items from our main catalogue. In this way, learning can be tailored to students’ individual needs, ranging from short basic experiments to advanced and complex topics.
This catalogue is organised under the following section-headings:
• PHY (Physics) includes the basics of generation, expansion and interaction of ultra sound and the principles of ultrasonic methods
• MED (Medicine) includes examples of experiments with medical applications and • IND (Industry) contains selected industrial applications of ultrasound and the topic of non-destructive testing.
The individual sets are presented under the following headings:
• PURPOSE describes the learning objectives of the experimental set, including the knowledge, skills and understanding a student would expect to gain
• MATERIAL lists all the equipment required with order-numbers and includes a photo graph of the set
• EXPERIMENTS lists all the experiments which can be carried out with this set • SUGGESTIONS FOR EXTENSIONS will help you combine other items to extend the learning for more able students.
Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
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Basics of ultrasound Set 1- Basics of ultrasound
Purpose With this set basic ultrasonic experiments can be accomplished. With the ultrasonic echoscope GAMPT-Scan the basics of ultrasound and its wave characteristics can be demonstrated. Terms like amplitude, frequency, sound velocity or Time Gain Control TGC will be explained. The cylinder set can be used to vividly demonstrate reflection and transmission as well as sound velocity and frequency depending on attenuation in solid state materials. The knowledge e.g. regarding sound velocity will be used to measure the testblock. The principles of image formation from A-scan to B-scan can be explained. With the different probes the frequency depending resolution can be evaluated.
Material list:
Experiments:
Ultrasonic echoscope GAMPT-Scan order no 10121 Ultrasonic probe 1 MHz order no 10131 2x Ultrasonic probe 2 MHz order no 10132 Ultrasonic probe 4 MHz order no 10134 Ultrasonic test block order no 10201 Ultrasonic cylinder set order no 10207 Ultrasonic gel order no 70200
PHY01 PHY02 PHY03 PHY06 PHY08
Ultrasonic echography (A-Scan) Velocity of ultrasound in solid state material Attenuation of ultrasound in solid state material Frequency dependence of resolution power Ultrasonic B-Scan
Suggestions for extensions: Shear wave set order no 10210 for Hydrophone set order no 10251 for Breast dummy order no 10221 for
PHY04 PHY07 PHY10 PHY20 MED02
Attenuation of ultrasound in liquids Shear waves in solid state materials Characteristic of sound field Determination of the focus zone Ultrasonic investigation with the breast dummy
Order no: SET01
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Ultrasonic experiments
Basics of ultrasound Set 2- Basics of ultrasound, medical applications
Purpose This set can be used to explain and illustrate the basics of ultrasound as well as some of its medical applications. With the ultrasonic echoscope GAMPT-Scan the basics of ultrasound and its wave characteristics can be demonstrated. Terms like amplitude, frequency, sound velocity or Time Gain Control TGC will be explained. With the testblock the principles of image formation from A-scan to B-scan and other charcteristics of ultrasound can be shown vividly. Additionally the frequency depending resolution can be evaluated . These basics can be used for medical applications. The experience from the test block can be used towards the B-mode evaluation of the breast dummy were a tumour has to be localised and measured. Another application of ultrasound in medicine is the Time Motion Mode. With the heart model the heart wall motion can be simulated and recorded.
Material list:
Experiments:
Ultrasonic echoscope GAMPT-Scan order no 10121 Ultrasonic probe 1 MHz order no 10131 Ultrasonic probe 4 MHz order no 10134 Ultrasonic test block order no 10201 Heart model order no 10220 Breast dummy with tumor order no 10221 Ultrasonic gel order no 70200
PHY01 PHY06 PHY08 MED01 MED02
Ultrasonic echography (A-Scan) Frequency dependence of resolution power Ultrasonic B-Scan Ultrasonic TM-mode Ultrasonic investigation with the breast dummy
Suggestions for extensions: Eye dummy order no 10222 for Cylinder set order no 10207 for Shear wave set order no 10210 for
MED04 PHY02 PHY03 PHY04 PHY07
Ultrasonic investigation with the eye dummy Velocity of ultrasound in solid state material Attenuation of ultrasound in solid state material Attenuation of ultrasound in liquids Shear waves in solid state material
Order no: SET02
Ultrasonic experiments
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Basics of ultrasound Set 3- Basics of ultrasound, applications for engineers and material science
Purpose In industry, one of the main applications of ultrasound in the industry are Non Destructive Tests (NDT). This set demonstrates the fundamentals of ultrasound as well as the basics of some of these tests. With the ultrasonic echoscope GAMPT-Scan the basics of ultrasound and its wave characteristics can be demonstrated. Terms like amplitude, frequency, sound velocity or Time Gain Control TGC will be explained. With the testblock the time of flight and the detection of discontinuities can be carried out. In addition, the frequency depending resolution can be evaluated. With the delay lines for angle beam and the test block for the angle beam test the adjustment of the angle test heads and their applications can be demonstrated. Using the test block with cracks the Time Of Flight Diffraction technique (TOFD) can be explained. Another application for ultrasound are level measurements of liquids which can be shown with a simple additional tank (reservoir).
Material list:
Experiments:
Ultrasonic echoscope GAMPT-Scan Ultrasonic test block Ultrasonic probe 2 MHz Ultrasonic probe 4 MHz Delay line for angle beam 17째 Delay line for angle beam 38째 Sample for angle beam test Test block with cracks Ultrasonic gel
order order order order order order order order order
no no no no no no no no no
10121 10201 10132 10134 10233 10234 10240 10241 70200
PHY01 PHY06 IND01 IND03 IND06 IND07
Ultrasonic echography (A-Scan) Frequency dependence of resolution power Non Destructive Testing Level measurement Angle beam measurement Time of flight diffraction technique (TOFD)
Suggestions for extensions: Shear wave set order no 10210 for Test block with discontinuities order no 10242 for
PHY04 PHY07 IND08
Attenuation of ultrasound in liquids Shear waves in solid state material Detection of discontinuities
Order no: SET03
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Ultrasonic experiments
Advanced applications of ultrasound Set 4- Advanced applications of ultrasound
Purpose Different wave modes of the ultrasound can be demonstrated and evaluated. With the ultrasonic echoscope GAMPT-Scan the basics of ultrasound and its wave characteristics can be demonstrated. Terms like amplitude, frequency, sound velocity or Time Gain Control TGC will be explained. With this set the differences between transmission and reflection measurement can be shown. The relation between distance and time of flight can be demonstrated exceptionally well in the reflection mode. Simultaneously the attenuation in water or other liquids can be evaluated. In solid state materials shear waves can be induced additionally to longitudinal waves. The border for such an induction is the angle of the total reflexion. With the different material samples of the shear wave set such shear waves can be generated and the relation between longitudinal and shear wave can be evaluated. With these measurements the elastic coefficents can be determined. Additionally, Rayleigh waves can be generated and their sound velocity be determined with this set using measurements from a special test block. The application of Rayleigh waves can be demonstrated with the NDT.
Material list:
Experiments:
Ultrasonic echoscope GAMPT-Scan Shear wave set Aluminum sample for shear waves 2x Ultrasonic probe 1 MHz 2x Ultrasonic probe 2 MHz 2x Rayleigh waves attachment Material sample for Rayleigh waves investigation Ultrasonic gel
order order order order order order
no no no no no no
10121 10210 10213 10131 10132 10231
PHY04 PHY07 IND02
Attenuation of ultrasound in liquids Shear waves in solid state material Rayleigh waves
order no 10232 order no 70200
Suggestions for extensions: Hydrophone set order no 10251 for Cylinder set order no 10207 for Ultrasonic testplates order no 10202 for
PHY10 PHY20 PHY02 PHY03 PHY05
Characteristic of sound field Determination of the focus zone Velocity of ultrasound in solid state material Attenuation of ultrasound in solid state material Spectral investigations
Order no: SET04
Ultrasonic experiments
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Debye- Sears effect Set 5- Debye-Sears
Purpose With this set the Debye-Sears effect and the projection of standing waves can be demonstrated. With the wave generator SC500 ultrasonic waves of different frequencies can be generated in a water bath. The waves act like lattice elements of an acoustic lattice, their lattice constant depends on the wave length of the ultrasound. With standing waves this lattice can be displayed as diffraction and projection image. With continuously progressing waves only the projection image can be displayed. This effect can be demonstrated with the ultrasonic absorber. The distances in the diffraction and projection image depend on the sound velocity in the liquid. This effect can be used to measure series of concentrations.
Material list:
Experiments:
Ultrasonic wave generator SC500 Complete set Debye-Sears Laser module green Sample reservoir (laser support) Tap for sample reservoir Lens holder Ultrasonic absorber
order order order order order order order
no no no no no no no
20100 20200 20211 20225 20223 20230 20227
PHY11 PHY12 IND04
Debye-Sears effect Projection of standing waves Concentration measurement
Suggestions for extensions: 2x Photodiode 2x Adjustable reflectors Semipermeable reflector
order no 20303 for order no 20302 order no 20301
PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice
Order no: SET05
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Ultrasonic experiments
Ultrasonic Doppler effect Set 6- Ultrasonic Doppler effect Purpose With this set the Doppler effect as well as basic flow phenomena can be demonstrated. With the ultrasonic pulse Doppler „FlowDop“ and an ultrasonic probe ultrasonic waves can be produced and frequency shifted scattering signals can be measured. With this set a flow circulation can be built containing various diameters and therewith different flow velocities. With the Doppler prisms various angles of incidence can be realised. In this way the relation between frequency shift of the Doppler effect, the angle of incidence, transmission frequency and flow velocity can be determined. With a flow profile the occurance of a laminar or turbulent flow can be measured. With the standpipes the pressure can be obtained on different points of the circulation. With the information relating to pressure, diameter and velocity fundamental characteristics of laminar flowing liquids like the Bernoulli equation and the Hagen-Poiseuille law can be investigated.
Material list: Ultrasonic pulse Doppler „FlowDop“ Ultrasonic probe 2 MHz Set prisms and flow pipes Centrifugal pump „MultiFlow“ Doppler dummy fluid Standpipe for pressure Ultrasonic gel
order order order order order order order
no no no no no no no
50100 10132 50201 50130 50140 50150 70200
Experiments: PHY13 PHY14 PHY15 IND05
Ultrasonic Doppler effect Flow profiles Mechanics of flow Flow measurement
Suggestions for extensions: Arm dummy Ultrasonic Doppler probe for
order no 50160 order no 50135
MED03 Doppler sonography
Order no: SET06
10 Ultrasonic experiments
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Ultrasonic Doppler effect Set 7- Ultrasonic Doppler effect in medicine (Doppler sonography)
Purpose This set helps to understand the Doppler effect and its application in medicine for blood flow measurements. With the ultrasonic pulse Doppler „FlowDop“ and a special Doppler probe ultrasonic waves can be generated and frequency shifted scattering signals can be measured. With the Doppler prisms various angles of incidence can be realised. In this way the relation between frequency shift of the Doppler effect, the angle of incidence, transmission frequency and flow velocity can be determined. With a flow profile the occurance of a laminar or turbulent flow can be measured. A realistic arm model is used to simulate the application of the Doppler effect in medicine. With a Doppler sonography the influence of a stenosis on the flow profile can be investigated. A pump generates different flow types (continuous and pulsatile) and can simulate the human blood circulation. The measured Doppler signals can be presented acoustically as well as in a colour-coded Doppler spectrum, whereas the results and images are not much different to measurements of those on patients.
Material list:
Experiments:
Ultrasonic pulse Doppler „FlowDop“ Ultrasonic probe 2 MHz Dopplerprism 3/8“ Ultrasonic Doppler probe Centrifugal pump „MultiFlow“ Arm dummy Ultrasonic gel
order order order order order order order
no no no no no no no
50100 10132 50112 50135 50130 50160 70200
MED03 Doppler sonography PHY13 Ultrasonic Doppler effect PHY14 Flow profiles
Suggestions for extensions: Standpipe for pressure order no 50150 Set prisms and pipes order no 50201
PHY13 PHY14 PHY15 IND05
Ultrasonic Doppler effect Flow profiles Mechanics of flow Flow measurement
Order no: SET07
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Ultrasonic experiments
Acousto-optical effects Set 8- Acousto-optical effects
Purpose This set is assembled for several challenging experiments dealing with the interaction between a mechanical wave and light. It demonstrates that the density changes of an ultrasonic wave provoke a change in the refraction index of the medium. The emerging lattice causes the diffraction of the light waves of the laser beam. In various experiments the characteristics of light diffraction on standing and travelling ultrasonic waves will be determined and measured. The sound velocity of the medium can be calculated from the determination of the interference maximum of the laser light. With a photodiode the amplitude modulation and the phase shift of the laser light caused by a standing wave can be recorded on an oscilloscope. The frequency variation of the sound wave affects the amplitude modulation allowing for the sound velocity of the medium to be calculated. The difference between the diffraction on a standing and travelling wave can be demonstrated with an ultrasonic absorber. At the travelling ultrasonic wave a frequency shift of the laser light can be measured caused by the Doppler effect. This difference can be demonstrated on the oscilloscope with the use of a beam splitter and the adjustable reflectors by producing a interference. The Doppler frequency shift of the light depends on the ultrasonic frequency and can be calculated from the measured frequencies. This experimental set is particularly suitable for the demonstration of the optoacoustic effect and its application in technology as well as developing interesting basic and advanced practical trainings in all scientific and technical fields of study.
Material list:
Experiments:
Ultrasonic wave generator SC500 Complete set Debye-Sears 2x photodiode 2x adjustable reflectors Semipermeable reflector Ultrasonic absorber
order order order order order order
no no no no no no
20100 20200 20303 20302 20301 20227
PHY17 PHY18 PHY11 PHY12 IND04
Sound velocity in water, acoustic lattice Phase shift on the acoustic lattice Debye-Sears effect Projection of standing waves Concentration measurement
Suggestions for extensions:
Order no: SET08
12 Ultrasonic experiments
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Ultrasonic computer tomography Set 9- Extension set- Ultrasonic computer tomography and scanning methods
Purpose This set is an extension to the ultrasonic pulse echo methods. Including automated imaging methods like CT and B-mode, scan methods can be determined e.g. to characterise the sound field. Xray as well as ultrasonic Computer Tomography are based on attenuation measurements and their evaluation using folding algorithms. The principle schedule of both methods is quite similar. With this set the development of a CT image can be demonstrated step by step. Furthermore, the ultrasonic tomogram gives sound velocity values for more image information which cannot be found in a pure attenuation picture. Automated B-scan images can be made with this set as well. The scanned objects can be measured and evaluated in axial and lateral direction. As sample the transparent or black test block can be used, for medical applications the breast dummy with tumor is recommended. The scanner can also be used for the determination of sound field characteristics of an ultrasonic probe. The sound field can be scanned axially e.g. to determine the near field length of the probe. Or the probe will be scanned laterally to measure how wide the sound field is. The ultrasonic echoscope GAMPT-Scan is necessary but not included in the set. If other items are existent already the set can of course be adapted. Some of the experiments can be done without scanner. The results of the automated measurements with scanner have a much better quality, especially with the imaging methods.
Material list: CT scanner order no 60100 CT control unit order no 60110 CT water tank order no 60120 CT sample order no 60121 2x ultrasonic probe 2 MHz order no 10132 Testblock transparent or black order no 10201/10204 Hydrophone order no 10250 Hydrophone holder order no 60123 Ultrasonic gel order no 70200 (not in set: Ultrasonic echoscope GAMPT-Scan order no 10121)
Experiments: PHY08 PHY09 PHY10 PHY16 PHY20
Ultrasonic B-Scan Ultrasonic computer tomography Characteristic of sound field Mechanical scan methods Determination of the focus zone
Suggestions for extensions: Breast dummy with tumor
order no 10221
for
MED02
Ultrasonic investigation with the breast dummy
Order no: SET09
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Ultrasonic experiments
Pulse echo ultrasonic methods Ultrasonic echoscope GAMPT-Scan The GAMPT-Scan is a highly sensitive ultrasonic measuring device designed to connect to a personal computer or simply to an oscilloscope. The supplied software enables an extensive signal processing (RF-signal, amplitude signal, B-scan, M-mode, spectral analysis). The ultrasonic probes are connected by robust snap-in plugs. The probe frequency is recognised automatically by the measuring device. By adjusting the power transmission and gain the ultrasonic signal can be tuned to nearly every arbitrary object of investigation. The loss of intensity of the ultrasonic signal from deeper layers of investigation is balanced by a time dependent amplification (TGC time-gain-control). Threshold, start and end point or slope can be chosen freely. Important signals (trigger, TGC , RF-signal and amplitude signal) are available at BNC outlets. For an experimental set up in lab course a large variety of ultrasonic probes (1 MHz, 2 MHz and 4 MHz) and accessories are available. The diversity of topics includes physical basics of ultrasound as well as medical and industrial applications. By employing the scanning system (GAMPT-60100 und 60110) many experimental setups for ultrasonic imaging methods can be realised. Technical data: Size Frequency PC connection Measuring operations Transmitter signal Transmitter power Gain TGC Outlets Main voltage Power of electricity
220 x 300 x 400 mm 1 - 5 MHz USB (parallel on request) reflection and transmission 10 - 300 Volt 0 - 30 dB 0 - 35 dB 0 - 30 dB, threshold, slope, width trigger, TGC, RF, LF 115/230 Volt, 50/60 Hz 20 VA
The supplied A-Scan software displays and evaluates the measured data on a computer connected via USB. Starting the program immediately activates the measuring system. The transmission frequencies of connected probes are recognized by a coding and appropriate parameters are adjusted. The current chosen adjustments (e.g. transmission level, receiver amplification, TGC etc) will be replicated by the device and displayed on the measurement screen. The current measured amplitudes are displayed as time dependent signals and are updated permanently. One can choose whether the RF-signal is shown or the amplitude signal envelope or both are displayed. By means of movable measuring marks first evaluations can be carried out (amplitude, time of flight, depth measurement). A freeze function as well as different zoom functions facilitate the evaluation. In addition to echo imaging (Amplitude scan) further evaluations can be carried out such as frequency analysis via fast Fourier transformation (FFT), the representation of two-dimensional ultrasonic (brightness) images (B-scan) or the process of moving reflection layers (time motion method) and the spectral and cepstral analysis of echo signals.
Experiments: PHY01 PHY02 PHY03 PHY04 PHY05 PHY06 PHY07 PHY08 PHY09 PHY10 PHY16
Ultrasonic echography (A-Scan) Velocity of ultrasound in solid material Attenuation of ultrasound in solid material Attenuation of ultrasound in liquids Spectral investigations Frequency dependence of resolution power Shear waves in solid state material Ultrasonic B-scan Ultrasonic computer tomography Characteristic of sound field Mechanical scan methods
PHY20 MED01 MED02 MED04 IND01 IND02 IND03 IND06 IND07 IND08
Determination of the focus zone Ultrasonic TM-mode Ultrasonic investigation with breast dummy Ultrasonic investigation with eye dummy Nondestructive material diagnosis Rayleigh waves Filling level measurement Angle beam measurement Time of flight diffraction technique (TOFD) Detection of discontinuities
Order no: 10121
14 Ultrasonic experiments
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Pulse echo ultrasonic methods Ultrasonic probe, frequency 1 MHz The ultrasonic probes distinguish themselves by a high sound intensity and short sound pulses. It makes them particularly appropriate for pulse-echo mode. All probes come with a robust metal box and are water proof protected at the sensor surface. The probes are delivered optionally with a special plug for connection to the GAMPT-Scan or with a BNC plug for universal use. The 1 MHz probes are suitable especially for large penetration depths because of their high sound intensity. Their use is recommended particularly for investigations of strong damping materials and for the generation of Rayleigh and shear waves, respectively. Thereby the probes can be utilised either as transmitter or as receiver. Technical data: Frequency 1 MHz Size l= 70 mm, d=27 mm Cable 1 m Sound adaptation to water/acrylic Special plug connector with probe identification for connection to GAMPT-Scan. universal plug connector BNC Experiments: PHY01 Ultrasonic echography (A-Scan) PHY02 Velocity of ultrasound in solid material PHY03 Attenuation of ultrasound in solid material PHY06 Frequency dependence of resolution PHY07 Shear waves in solid state material PHY08 Ultrasonic B-Scan
PHY16 PHY20 MED02 IND02
Mechanical scan methods Determination of the focus zone Ultrasonic investigation with breast dummy Rayleigh waves
Order no: 10131 Order no: 10141 (BNC)
Ultrasonic probe, frequency 2 MHz The 2 MHz probes are suitable for a wide range of uses. Because of the higher frequency the axial and lateral resolution power is clearly better compared to the 1 MHz probe. On the other hand the damping of 2 MHz sound in most materials is not yet too large, so investigations in middle depth can be obtained easily. These probes are especially suitable for investigations on medical objects and used as ultrasonic Doppler probes. Technical data: Frequency 2 MHz Size l= 70 mm, d=27 mm Cable 1 m Sound adaptation to water/acrylic Special plug connector with probe identification for connection to GAMPT-Scan. Universal plug connector BNC Experiments: PHY02 Velocity of ultrasound in solid material PHY03 Attenuation of ultrasound in solids material PHY04 Attenuation of ultrasound in liquids PHY05 Spectral investigations PHY08 Ultrasonic B-Scan PHY09 Ultrasonic computer tomography PHY10 Characteristic of sound field PHY13 Ultrasonic Doppler effect PHY14 Streaming profiles
PHY15 PHY16 PHY20 IND01 IND03 IND05 IND06 IND07 IND08 MED04
Rules of streams Mechanical scan methods Determination of the focus zone Nondestructive material diagnosis Filling level measurement Flow measurement Angle beam measurement Time of flight diffraction technique (TOFD) Detection of discontinuities Ultrasonic investigation with eye dummy
Order no: 10132 Order no: 10142 (BNC)
Ultrasonic probe, frequency 4 MHz The 4 MHz probe is distinguished by an extreme short oscillation decay time which results in the highest axial resolution power. This probe is used especially for the detection of very small structures. Mainly for investigations performed in liquids the limited penetration depth of some materials is no problem. This probe in particular is recommend for investigations on thin plates and for ultrasonic CT due to its high resolution power and related spectral bandwidth. Technical data: Frequency 4 MHz Size l= 70 mm, d=27 mm Cable 1 m Sound adaptation to water/acryl Special plug connector with probe identification for connection to GAMPT-Scan. Universal plug connector BNC Experiments: PHY03 Attenuation of ultrasound in solids material PHY06 Frequency dependence of resolution PHY20 Determination of the focus zone
MED01 IND06
Ultrasonic TM-mode Angle beam measurement
Order no: 10134 Order no: 10144 (BNC) www.gampt.de
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15 Ultrasonic experiments
Pulse echo ultrasonic methods Adapter BNC LEMO for GAMPT-Scan The adapter enables the connection of ultrasonic probes with BNC connector to the LEMO sockets of the GAMPT-Scan. Attention: the GAMPT-Scan and the GAMPT-probes are adjusted to eachother. Before using probes of other manufacturers please check if the technical parameters are compatible. Technical data: Length
1m
Order no: 10270
Ultrasonic test cylinder set (estimation of sound velocity and damping) The velocity of sound, impedance of sound and the damping are typical material specific parameters which can be determined in reflection or transmission using these three acrylic cylinders. The determination of sound velocity for three objects of varying length requires a detailed error discussion. The results of the damping in transmission at different ultrasonic frequencies gives basic relations of ultrasonic absorption in solid state materials. Technical data: Size Material Sound velocity Density Damping
D= 40 mm, l= 40, 80, 160 mm acrylic, transparent ~2670 m/s 1,2 g/cm続 ~3-12 dB/cm @1-4 MHz
Experiments: PHY02 Velocity of ultrasound in solid material PHY03 Attenuation of ultrasound in solid material PHY05 Spectral investigations
Order no: 10207 (set)
Replacements: Order no: 10203 (cylinders) Order no: 10215 (probe support) Order no: 10205 (holder block)
Ultrasonic test plates This pair of thin acrylic plates is used for a number of interesting ultrasonic spectral investigations. The echo image displays multiple reflections due to the plates material weakness. The spectral evaluation of single reflexes shows an increasing shift of the spectrum to lower frequencies due to the frequency dependent damping. In the spectrum of all reflexes the thickness of plates is involved as periodic modulation. By superimposing several plates of a different thickness, one obtains a diffuse echo image whose spectrum contains also diffuse modulations. Only by evaluating the cepstrum the individual thickness of plates can be determined. The set includes an acrylic delay block. Technical data: Size 40 x 80 mm Thickness 7, 10 mm Material acrylic, transparent Sound velocity ~2670 m/s Density 1,2 g/cm続
Experiments: PHY05
Spectral investigations
Order no: 10202 16 Ultrasonic experiments
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Pulse echo ultrasonic methods Shear wave set with acrylic sample When an ultrasonic wave hits a solid state material angular, shear waves will be generated with increasing angle. Shear waves have a sound velocity differing to that of longitudinal waves. With this experimental equipment the transition from longitudinal to shear waves can be measured angle-dependently. The measurement is carried out in transmission with two fixated probes (1 or 2 MHz). The sample support can be moved along the reservoir in longitudinal direction and the angle be readout on a scale. From the measurements of longitudinal and transversal sound velocity the elastic constants of the material can be determined. This experimental set up is also suitable for the determination of absorption in liquids (oil, glycerin) due to the adjustable sample plate. Technical data: Sample support with angle scale 0 - 360째 in steps of 5째 Sample material acrylic, transparent Sound velocity longitudinal ~2670 m/s; transversal ~1450 m/s 2 probe supports acryl, black 1 reservoir to hold the sample support
Experiments: PHY04 PHY07
Attenuation of ultrasound in liquids Shear waves in solid state material
Order no: 10210 (set)
Replacements: Order no: 10214 (reservoir) Order no: 10215 (probe support) Order no: 10205 (holder block) Order no: 10211 (acrylic sample)
Aluminum sample for shear waves To determine the elastic constants via longitudinal and transversal sound velocity a further sample material is available. In aluminum the longitudinal as well as the transversal sound velocity are larger than in water. Technical data: Material aluminum Sound velocity longitudinal ~6400 m/s transversal ~3100 m/s Experiments: PHY04 PHY07
Attenuation of ultrasound in liquids Shear waves in solid state material
Order no: 10213
POM sample for shear waves To determine the elastic constants via longitudinal and transversal sound velocity a further sample material is available. In POM the transversal sound velocity is smaller than the sound velocity in water. Technical data: Material POM Sound velocity
longitudinal ~2470 m/s transversal ~1200 m/s
Experiments: PHY04 PHY07
Attenuation of ultrasound in liquids Shear waves in solid state material
Order no: 10212
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
Pulse echo ultrasonic methods Ultrasonic test block The ultrasonic test block made from homogeneous acrylic is suitable especially for echography investigations. Acrylic is a material possessing a low acoustic damping, sufficient for the penetration depth of all probes. The block has a group of voids with different sizes in different depths, a big void (to see acoustic shadow) and a double void for resolution test. Basic knowledge can be obtained regarding the determination of sound velocity, echo methods, acoustic shadow, multiple reflections, zones of focus and the resolution power of ultrasound of different frequencies. The block can be delivered as transparent acrylic with visible voids or as black acrylic with hidden voids. Technical data: Size 150 x 80 x 40 mm Material acrylic, transparent Sound velocity ~2670 m/s Density 1,2 g/cm続 Voids 11
Experiments: PHY01 PHY06
Ultrasonic echography (A-Scan) Frequency dependence of resolution power
PHY08 PHY16 IND01
Ultrasonic B-Scan Mechanical scan methods Nondestructive material diagnosis
Order no: 10201 (transparent)
Ultrasonic test block The ultrasonic test block made from homogeneous acrylic is suitable especially for echography investigations. Acrylic is a material possessing a low acoustic damping, sufficient for the penetration depth of all probes. The block has a group of voids with different sizes in different depths, a big void (to see acoustic shadow) and a double void for resolution test. Basic knowledge can be obtained regarding the determination of sound velocity, echo methods, acoustic shadow, multiple reflections, zones of focus and the resolution power of ultrasound of different frequencies. The block can be delivered as transparent acrylic with visible voids or as black acrylic with hidden voids. Technical data: Size 150 x 80 x 40 mm Material acrylic, black Sound velocity ~2670 m/s Density 1,2 g/cm続 Voids 11
Experiments: PHY01 PHY06
Ultrasonic echography (A-Scan) Frequency dependence of resolution power
PHY08 PHY16 IND01
Ultrasonic B-Scan Mechanical scan methods Nondestructive material diagnosis
Order no: 10204 (black)
Rayleigh waves attachment With this attachment it is possible to generate and receive surface waves (Rayleigh waves) in a solid sample (fitted to aluminum). Therefore the sound velocity of the Rayleigh waves as well as information about surface faults of materials can be determined. The attachment is manufactured direction dependent in order to optimise the signal amplitude. It is especially adapted to a probe of 1 MHz. Technical data: Material Frequency Raleigh wave Initiation frequency Diameter Height
acrylic 1 MHz 1 MHz 32 mm 10 mm
Experiments: IND02
Rayleigh waves
Order no: 10231 18 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Pulse echo ultrasonic methods Material sample for Rayleigh waves investigations This sample for the investigation of Rayleigh waves has an undisturbed surface side on which the sound velocity of Rayleigh waves can be determined in transmission mode. Another side has several material defects which can be detected and localised by Rayleigh waves. A special method in the material inspection is the measurement of crack depth by means of Rayleigh waves. Thereby the signal amplitude of the surface wave is measured and the depth of the material crack can be determined. The sample has several cracks on the third side down to 6 mm depth. Technical data: Material aluminum, Size 35 x 35 x 600 mm Weight 2,5 kg Sound velocity Raleigh waves ~2950 m/s Different voids
Experiments: IND02
Rayleigh waves
Order no: 10232
Delay line for angle beam 17°, 38°, 56° One of the most important methods of destruction free inspection by ultrasound is the angle beam test. From the sound velocity of the delay line and of the material under investigation the angle of incidence results according to the law of refraction of the longitudinal and the shear wave. The delay line is suited for the test of transmission, reflection and when using two lines for the double transducer technique. The angle beam adapter can be utilised with all GAMPT-probes (1, 2, 4 MHz). Technical data: Material Sound velocity Incident angle Resulting angle aluminum shear wave Resulting angle aluminum longitudinal wave
acrylic ~2670 m/s 17°, 38°, 20° 45° 45°
56° 70°
Experiments: IND06 IND07 IND08
Angle beam measurement Time of flight diffraction technique (TOFD) Detection of discontinuities
Order no: 10233 (16,8°) Order no: 10234 (38,5°) Order no: 10235 (55,8°)
Sample for angle beam test The aluminum test sample serves for the adjustment of the angle test heads with regard to the angle of incidence, the sound velocity, the position of the sound exit and the length of the delay line. Thereby the angle is determined by the measurement of the wall echoes in different projection distances. Adjustment checks are carried out on a cylindrical drilling. Technical data: Material Sound velocity Size Drilling
aluminum longitudinal ~6400 m/s transversal ~3100 m/s 35 x 3 mm, 5 x 120 mm D = 8 mm
Experiments: IND06
Angle beam measurement
Order no: 10240 19 www.gampt.de
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
Pulse echo ultrasonic methods Test block to determine crack depth The test block contains cracks in different depths. By means of two different measuring techniques the cracks can be localized and their depth can be determined. First using an angle test head the angle dependent echo amplitude is determined in dependence of the depth of cracks. However, for greater crack depth this procedure fails. By means of the TOFD-mode, cracks in greater depth can be located and measured too. The capabilities and limits of both methods are determined and demonstrated with this test block. Technical data: Material Sound velocity Size Crack depth
aluminum longitudinal ~6400 m/s transversal ~3100 m/s 35 x 35 x 300 mm 2, 4, 6, 8, 10, 15 mm
Experiments: IND07
Time of flight diffraction technique (TOFD)
Order no: 10241
Test block with acoustic discontinuities The test block of aluminum contains different types of reflectors which are used for the generation of echoes. Five mirror-like reflectors and a crack-like reflector are distinguished. As mirror-like reflectors a cylinder, a circular disc, a wall and an angle mirror with different alignment at the surface are used respectively. Diffraction effects can be localised at the crack. For the location various techniques are used such as echo-method, delta-method, tandem-method, transfer-method and angle-method. Technical data: Material Sound velocity Size Discontinuities
aluminum longitudinal ~6400 m/s transversal ~3100 m/s 35 x 35 x 300 mm 6
Experiments: IND08
Detection of discontinuities
Order no: 10242
Hydrophone set By means of the pointed hydrophone the characteristic of the sound field of an ultrasonic probe can be measured. Thus from the modulation of amplitude in the direction of the central axis of the sound probe the near field length and the focus zone are determined, respectively. As well the lateral extension of the sound field can be measured for different distances from the probe surface. The hydrophone is applicable in the frequency range of 1 - 5 MHz. It can be connected directly to the input connector of the GAMPT-Scan. The measurements are carried out simply by shifting the hydrophone by hand or by using the CT-scanner. For both variants a suitable support for the hydrophone is on hand. Technical data: Material aluminum Active sensor area D= 3 mm Frequency range 1 – 5 MHz Experiments: PHY10 Characteristic of sound field PHY19 Phase and group velocity
Order no: 10251 (set)
PHY20
Determination of the focus zone
Replacements: Order no: 10250 (hydrophone) Order no: 10252 (hydrophone plate) Order no: 10215 (probe support) Order no: 10214 (reservoir) Order no: 60123 (hydrophone holder)
20 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Pulse echo ultrasonic methods Breast dummy with tumor simulation The breast dummy from silicone rubber has two inclusions. With these benignant tumors are simulated. First of all the position of the tumor can be felt in order to carry out an exact ultrasonic investigation. By a hand guided B-scan (compound scan) or by imaging in linear scanning respective (better resolution by improved coupling and local assignment) the tumors are well displayed. Position and size of the tumor can be determined from the B-scan. In this way the breast phantom fits very well as a sample in the ultrasonic training of physicians. Technical data: Breast dummy, silicone 2 movable inclusions, depth 10 mm, diameter ca. 20 mm
Experiments: MED02
Ultrasonic investigation with the breast dummy
Order no: 10221
Model of human eye for biometric measurements Biometric measurements with ultrasound are an important diagnostic method in the ophthalmology. The typical biometric measurements of the length of eye axis suit excellent to demonstrate the basics of ultrasonic pulse echo applications. With this model and the ultrasonic device GAMPT-Scan (GAMPT-10121) with an 2 MHz probe one will receive typical echoes of the eye. The eye consists of a lens and the vitreous body with different sound velocities. The geometrical dimensions of these objects can be determined by the distances of the echoes. Additionally a lesion near the eye background with a diffuse echo structure is detectable. Technical data: Eye model with lens and vitreous body Scale 1:3 Size 80 mm diameter Experiments: MED04
Ultrasonic investigation with the eye dummy
Order no: 10222
Heart model, ultrasonic time motion mode To investigate running movements by ultrasonic imaging the TM-mode (time motion mode) is used. Thereby the echoes along the sound axis are recorded. In this way movements of heart valves and heart walls can be registered. The heart model contains a movable membrane, whose echo generates a TM-image similar to the movements of heart valves and heart walls. The membrane is bend upwards periodically by means of a rubber ball. By a slow back stream of air one obtains a characteristic course of the curve. From the measured curves the speed of walls and the volume per heart beat can be calculated. Technical data: Double cup with rubber membrane Rubber ball
Experiments: MED01
Ultrasonic TM-mode
Order no: 10220
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
cw (continuous wave) methods Multi frequency ultrasonic continuous wave generator SC500 (cw-generator) The ultrasonic generator SC500 is an advancement of the SC300 and replaces it completely. It enables the generation of continuous sound waves with high power over a wide frequency range (up to 20 MHz). Therefore the transmission frequency can be changed digitally in steps of 1 Hz and is displayed. The sound power can be controlled by the voltage at the ultrasonic probe, it can be switched on or off separately, the transmission status is shown by a LED. The value of the transmitting voltage is shown on a LCD-display. At the output is a sinus shaped signal with a maximum amplitude of 40 V. Additionally, the transmission frequency is given as a TTL signal at a second outlet. For the Debye-Sears experiment or the central projection of standing waves laser diodes are needed. For this the cw-generator has an according output integrated. It can also be switched separately and has its own control LED. The SC500 is designed especially for the connection with the GAMPT multifrequency probe. Ultrasonic waves in a range from 1–13 MHz can be generated. Technical data: Frequency Frequency steps Signal amplitude Output Size Main voltage
<= 20 MHz 1 Hz 2 - 40 V - transmitter signal sinus shaped, disconnectiable, with control LED - TTL, rectangularly - Sinus wave, adjustable - laser diode, adjustable, disconnectable, with control LED 256 x 185 x 160 mm 90 – 230 Volt, 50/60 Hz
Experiments: PHY11 Debye- Sears effect PHY12 Projection of standing waves PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice PHY19 Phase and group velocity IND04 Concentration measurement
Order no: 20100
Complete set Debye-Sears effect The generation of standing waves for the Debye-Sears effect and the central projection is done in a special reservoir. There is a probe support to adjust the incident wave exactly vertical to reach optimal wave interferences. Additionally, there is a support for the laser module with a lens holder, so the laser beam is orthogonal to the sound wave direction. To generate a divergent laser beam (needed for central projection) a lens can be added into the holder. Technical data: Sample reservoir Probe support Ultrasonic probe Laser module
glass, 105 x 125 x 100 mm, with support for laser module POM, 3 point adjustment, 105 x 125 x 50 mm 1 – 13 MHz, metal box red, 652 nm
Experiments: PHY11 Debye- Sears effect PHY12 Projection of standing waves PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice IND04 Concentration measurement
Order no: 20200 (set)
Replacements: Order no: 20225 (sample reservoir) Order no: 20224 (probe adjustment) Order no: 20138 (probe) Order no: 20210 (laser red)
22 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
cw (continuous wave) methods Probe adjustment for the sample reservoir The adjustment covers the sample reservoir and has a support for the multi frequency probe. The probe can be fixed with a screw. The flexible bounded support can be adjusted with three screws so the probe and with it the sound wave direction can be aligned optimally to the laser beam. A standing wave can be created with an exact vertical oriented sound wave and a distance adapted to the reflection wall and the wave length. So one can create optimal diffraction pattern and sharp images of the central projection. Technical data: Material POM Size 105 x 125 x 50 mm 3 point adjustment with probe support Experiments: PHY11 PHY12 PHY17 PHY18 IND04
Debye- Sears effect Projection of standing waves Sound velocity in water, acoustic lattice Phase shift on the acoustic lattice Concentration measurement
Order no: 20224
Sample reservoir with laser support The sample reservoir from glass is suitable for all liquids, easy to clean and has with the plane base and walls optimal properties for sound reflection to generate standing waves. With the fix installed laser diode support the laser beam has an orthogonal direction to the walls, so only the ultrasonic probe has to be adjusted. Additionally, inside the laser support is a slot to input a lens holder. The lens is used to generate a divergent laser beam. For sound velocity measurements with the Debye-Sears effect in different liquids or with different concentrations more than one sample reservoir can be used, e.g. the different concentrations have their own sample reservoir, during the measurement only the adjustment with the probe support can be moved fast from one reservoir to the other. Technical data: Material glass, 4 mm Size 105 x 125 x 100 mm Experiments: PHY11 Debye- Sears effect PHY12 Projection of standing waves PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice IND04 Concentration measurement
Order no: 20225
Multifrequency probe This ultrasonic probe is designed especially for the use with the multifrequency cw generator. It is characterised by very good sound generation properties in a frequency range from 1 MHz up to over 10 MHz. In this way all experiments with the cw generator can be done over a wide frequency range with only one ultrasonic probe. Like all GAMPT probes it has a robust metal box and is water proof protected at the sensor surface. This one has a special cable for high sound capacity and continuous operation. Technical data: Frequency 1 â&#x20AC;&#x201C; 13 MHz Size 65 x 27 mm Cable 1m Experiments: PHY11 Debye- Sears effect PHY12 Projection of standing waves PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice PHY19 Phase and group velocity IND04 Concentration measurement
Order no: 20138 23 www.gampt.de
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
cw (continuous wave) methods Laser module, red The red laser with a wavelength of ~650 nm has a special housing for easy positioning in the laser support of the sample reservoir. The laser diode has the protection class II and will be connected to the cw generator and gets the according voltage from there. All laser modules are individually wavelength measured and logged. In this way the error of measurement concerning the laser light wavelength should be minimised during the experiments. Technical data: Wavelength Power Size Voltage Current consumption Protection class
~ 650 nm < 1 mW l= 90 mm, d= 17 mm <= 3 V DC max. 30 mA II
Experiments: PHY11 Debye- Sears effect PHY12 Projection of standing waves PHY17 Sound velocity in water, acoustic lattice PHY18 Phase shift on the acoustic lattice IND04 Concentration measurement
Order no: 20210
Laser module, green The green laser with a wavelength of ~532 nm has a special housing for easy positioning in the laser support of the sample reservoir. The laser diode has the protection class IIIa and will be connected to the cw generator and gets according voltage from there. All laser modules are individually wavelength measured and logged. In this way the error of measurement concerning the laser light wavelength should be minimised during the experiments. Technical data: Wavelength Power Size Voltage Current consumption Protection class
~ 532 nm < 5 mW l= 90 mm, d= 17 mm <= 3 V DC max. 250 mA IIIa
Experiments: PHY11 PHY12
Debye- Sears effect Projection of standing waves
Order no: 20211
Projection lens for the projection of standing waves The projection lens is built from a rectangular glass carrier with a glued plano-concave lens (focal distance = 10 cm). At the projection experiment the lens will be put into the slot of the laser support of the sample reservoir. Doing so the optical lens is between laser source and ultrasonic wave and the standing sound wave is crossed by a divergent laser beam. By simple putting in or out of the lens a fast change between diffraction and projection is possible. Technical data: Carrier size Lens diameter Focal distance
25 x 75 mm d= 16 mm f= 100 mm
Experiments: PHY12
Projection of standing waves
Order no: 20230 24 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
cw (continuous wave) methods Cover for sample reservoir When more than one sample reservoirs are used the cover should help to prevent evaporation and with it changes in the concentration of the liquid. Additionally, it helps to prevent contaminations. Technical data: Material Size
POM 105 x 125 x 50 mm
Experiments: PHY11
Debye- Sears effect
Order no: 20223
Ultrasonic absorber The absorber is able to absorb in most of the incident ultrasonic wave. Its acoustic properties are adjusted to water. The part of the sound which cannot be absorbed will be reflected evenly. Technical data: Material Size
Silicone 90 x 110 x 19 mm
Experiments: PHY12 PHY18
Projection of standing waves Phase shift on the acoustic lattice
Order no: 20227
Ultrasonic coupling gel For the acoustic coupling of ultrasonic probes to samples a coupling medium must be used. For this various oils and first of all water are utilised. For lab course the use of ultrasonic gel from medical diagnostics is recommended. These gels have a high viscosity but do not contain any oily components (there is no danger of contamination). The ultrasonic gel is water-soluble, skin-friendly and not poisonous. Technical data: Water-soluble, hypo allergenic Bottle with ultrasonic gel 250 ml
Order no: 70200 25 www.gampt.de
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
cw (continuous wave) - methods Semipermeable reflector The semipermeable reflector is used as beam splitter for the laser light. The ratio transmission/reflection is 1:1 Technical data: Reflector size Size
17 x 11 mm 90 x 60 x 80 mm
Experiments: PHY17 PHY18
Sound velocity in water, acoustic lattice Phase shift on the acoustic lattice
Order no: 20301
Adjustable reflector With the three point adjustment the reflector area can be tilted horizontally as well as vertically. It enables a very exact alignment of the laser beam to the target object (e.g. semipermeable reflector, photodiode). Technical data: Reflector size Size
48 x 48 mm 90 x 60 x 80 mm
Experiments: PHY17 PHY18
Sound velocity in water, acoustic lattice Phase shift on the acoustic lattice
Order no: 20302
Photodiode With the photodiode with integrated amplifier a quantitative recording of the intensity of the laser light is possible. In this way the amplitudes of the diffraction orders can be measured and appearing modulations (AOM) can be analysed with an oscilloscope. Technical data: Photodiode: Spectral area of sensitivity (10% from max) Maximum photo sensitivity Light sensitive area Power supply: Amplifier output: Size
400-1100 nm 850nm 7mm² 12V 500mW BNC 0..10V 90 x 60 x 80 mm
Experiments: PHY17 PHY18
Sound velocity in water, acoustic lattice Phase shift on the acoustic lattice
Order no: 20303
26 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
EQUIPMENT FOR MEDICAL EDUCATION
Laminar flow
Modification of flow
Turbulent flow
Pulsatile flow
Experimental setup with ultrasonic Doppler device „FlowDop“
Frequency dependence of resolution power Purpose:
Setup:
By means of two neigh bouring defects the different axial resolution power of a 1 MHz and a 4 MHz ultrasound probe is examined. Therewith the relation between wavelength, frequency, pulse length and resolution power is illustrated.
Ultrasonic echoscope GAMPT-Scan 2 x Ultrasonic probes 1 MHz 2 x Ultrasonic probes 4 MHz Ultrasonic test block
order no GAMPT-10121 order no GAMPT-10131 order no GAMPT-10134 order no GAMPT-10201
Ultrasound computer tomography Purpose:
Setup:
The several steps of the formation of a computer tomography are illustrated. Especially for ultra sound the difference between damping and sound velocity as measuring parameters are analyzed. The influence of filtering and image processing is investigated.
Ultrasonic echoscope GAMPT-Scan Computerised Tomography Scanner CT control unit 2 x ultrasonic probes 2 MHz 2 x probe support CT sample attenuation CT sample sound velocity Water tank
Ultrasonic TM-mode
order order order order order order order order
no no no no no no no no
GAMPT-10121 GAMPT-60100 GAMPT-60110 GAMPT-10132 GAMPT-10215 GAMPT-60121 GAMPT-60122 GAMPT-60120
Setup: Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 4 MHz Heart model
For the generation of the sound velocity tomogram the time of flight is used as measuring quantity and the following is valid: c∝
(2)
Heart Diastole
t0 t
The sample (damping or velocity sample) is attached to the sample holder and by means of the scanner control that is positioned exactly between the two sensors. Then the sample holder is moved half of the scanning way, the accuracy of scanning and the number angle intervals are adjusted and the CT scan is started. During the measurements the individual line scans are observed and the generation of the tomograms by superposition of the projections of line scans is studied. The resulting images are optimized by means of various filters and by brightness and contrast adjustments and then the damping tomogram is compared with the velocity tomo-
Basics:
Basics:
Procedure: First of all the frequency of the probe is determined at a slightly damped echo. For this the echo of a near the surface localized defect is examined at a test block. By means of the power of transmitter and receiver and the TGC a suitable RFsignal is adjusted. With both measuring lines the pulse length and the distance is measured for a number of oscillations in the time range and from this the frequency is calculated. It is recommended to use the zoom function for the 4 MHz probe. Then consequently the double defect of the test block is investigated with the 1 MHz and 4 MHz probe respectively. In the echogram the distance of both defects is measured.
As image forming physical quantities for ultra sound tomography the attenuation of sound and the sound velocity are utilized. The attenuation coefficient of sound µ results from measured amplitude A and the amplitude without sample A0 after the law of attenuation: (1)
µ ∝ Ln
gram.
A0 A
Results: Results: The determination of the frequency of probes from the echo in the time range shows deviations to the nominal frequency: 1 MHz: T = 4,7 µs / 5 periods f= 1,06 MHz 4 MHz: T = 1,3 µs / 5 periods f= 3,85 MHz These deviations are caused by the frequency dependent damping, the large bandwidth of a pulse probe and the relative large error in measurement at the time limited resolution of the echoes. The determination of the pulse length shows distinctly longer pulses for lower ultrasound frequency. Pulse length: 1 MHz 10 µs 4 MHz 3 µs During the investigation of the double defect it appeared that the holes can not be resolved by the 1 MHz probe. There is only one peak for both holes. The echogram using 4 MHz shows two distinctly separated peaks. The time distance of the peaks was determined to 1.3 µs. With a velocity of sound of 2680 m/s the hole distance amounts to 1,7 mm. (Control measurements by the calliper: 1.6 mm)
echo of the 1 MHz probe
echo of the double hole with the 1 MHz probe
echo of the 4 MHz probe
The transmission signal (the diagram left above) has been measured with regard to maximal amplitude and time of flight of the maximal amplitude and from this a line profile (scan at one angle, 500 µm point distance) has been built (diagram left below). The superposition by means of the CT-algorithm (25 angle intervals) yields for sound attenuation the image left above (non filtered, contrast changed) and for the sound velocity the image right above (also non filtered, contrast changed). A filtering (images below) yields in the case of the attenuation image (left) a contrast improvement. While in the attenuation image mainly the edges become visible (reflection losses) and the inner part hardly distinguishes from the surrounding water, in the sound velocity image (right) the sample and the inclusion are good visible as homogeneous regions of a different sound velocity.
Setup: Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 4 MHz Heart model
Results:
Figure 1 show a continuously (venous) flow with a mean Doppler shift of ca. -700Hz. The minus in the Doppler shift means: flow away from the probe. Figure 2 is the spectral distribution with rotated probe. Flow towards the probe (the same Doppler shift, but positive). Figure 3 is the Doppler spectral figure of a stenosis. The differences to a normal (healthy) figure like figure 1 are: 1. A local increase of the maximum Doppler shift (maximum flow velocity). 2. A decrease of mean frequency and a broadening of the spectra. 3. A increase of reflux phenomenon (negative and positive parts of the spectra). Figure 4 shows the pulsatile flow of P1 with an pulse rate of ca. 90min-1.
Purpose:
Setup:
The basics of generation of ultrasonic B (Brightness) -scans are shown with a simple sample object. Thereby the characteristics of image quality are explained, like focus zone, resolution power and artefacts.
Ultrasonic echoscope GAMPT-Scan 2 x Ultrasonic probes 1 MHz 2 x Ultrasonic probes 2 MHz Ultrasonic test block
(3)
(1)
Df = f 0
v ( cos A + cos B ) c
where a and b are the angles between v and the wave normal. For a pulse-echo-system with a ultrasound sensor a =b is valid and therefore:
Df = 2 f 0
v cos A c
Results:
angle of prism 15°
Doppler angle 81,7°
30° 60°
73,8° 61,1°
cos (a) 0,144 0,279 0,483
15°
30°
60°
Df [Hz] v [cm/s] Df [Hz] v [cm/s] Df [Hz] v [cm/s] 185 285 405
48 74 105
342 515 700
46 69 93
570 920 1320
44 71 102
The upper diagram shows that the Doppler frequency shift increases with increasing voltage (velocity) and decreasing Doppler angle. The lower diagram shows that for one velocity the ratio of DF/cos(a) is constant therefore no angle dependent error measurement occurs. Figure 2
cL ) cP
Setup: Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Ultrasonic test block
(1)
s = c*t/2.
By knowing the velocity of sound of the material under investigation therefore the distance of a defect can be determined directly from the time of flight. The amplitude of the ultrasound echo depends on the damping of the material between probe and defect , the difference of impedance of material and defect as well as on the geometric form and orientation of the defect.
Procedure:
Basics: At the ultrasound section image the echo amplitude is shown as a gray scale value (brightness -> B-scan) and the time of flight as penetration depth. The lining up of several adjacent A-scan lines results in the section image. For this the probe will moved lengthwise over the area of interest, the local assignment alongside this movement is done with the position and the speed of the probe. A simple form of generation B-scan is slow move of the probe by using the hand (compound scan). Thereby a precise lateral local power resolution is only possible with additional systems to get the coordinates like i.e. linear scanner. However with the arbitrary slow scan speed it is possible to generate images with high quality in a wide area of interest. The image quality depends of following parameters: -precise registration of the coordinates (scanner system) -axial power resolution (ultrasonic frequency) -lateral power resolution (ultrasonic frequency, geometry of the sound field) -gray scale resolution (transmission power, amplification, TGC) -number of scan lines ( speed of probe movement) -aberrations (sound shadows, movement artefacts, multiple reflections)
order no GAMPT-10121 order no GAMPT-10131 order no GAMPT-10201
The longest side of the sample (GAMPT-10201) is measured by a calliper or ruler. Then the ultrasound transducer is coupled by a coupling gel to the sample and the echoscope is adjusted concerning power of transmitter, basic amplification and TGC so that the echo of the back side is good visible. The time of flight up to the echo is measured and by using the edge length after (1) the velocity of sound of the material is determined. This fed to the software and switch the display to „depth“. Now the distance to the defect can be measured directly. All defects of the sample are measured either relative to both long sides (so the extension of the defect can be determined) or are measured from two sides perpendicular to each other in order to find the precise position of the defect.
Basics: Using ultrasound echoscope an ultrasound probe coupled to the medium under investigation is excited by a short pulse. The emitted ultrasound wave is reflected at inhomogeneities of the sound impedance and this reflection is detected by the same transducer. The time of flight t between the start of pulse at transmitter and the appearance of the echo is related via the velocity of sound c of the medium with the distance s of the defect from the ultrasound probe in he following way:
Results:
results and velocity of the movement:
pump voltage [V] 3,00 5,00 7,00
A = 90° − arcsin ( sin A P
By means of the Doppler-angle and the measured Doppler frequency shift Df the mean velocity of flow is calculated via (2) (fo=2 MHz).
Purpose: The relation between time of flight of ultrasound echoes, the velocity of sound and the distance between ultrasound transducer and defect (reflector) for different size of defects is determined. For this the adjustments at the device must be optimized concerning the corresponding echo (i.e. power of transmitter, basic amplification and time gain control (TGC)). Then the velocity of sound of the sample shall be determined and the position and size of the defect be measured.
To generate a B-scan at first estimate the sound velocity of the acrylic block. Following this the test block will measured as A-scan with suitable adjustments for transmitter and receiver, so that also signal amplitudes from objects near the surface are not saturated. Important beyond everything else for this is the TGC. For the acoustic coupling of the ultrasound probe the use of a water film is recommended, the ultrasonic gel has a strong static friction. Input the size and the sound velocity of the test block into the B-scan software. After starting the measurement move the probe with constant speed over the block. The dependence of the image quality can shown by variation the adjustments and the scan speed Additional the effect of the used ultrasonic frequency to the lateral resolution can shown by using a 2 MHz probe
Procedure: At a 3/8“ tube as measuring distance the Doppler-prism is attached. On the control of the centrifugal pump three different flow velocities (voltages) are adjusted and at each angle of the prism (aP= 15° , 30° and 60° ) the shift of Doppler frequency is determined for each velocity. From the known sound velocities in the liquid (cl=1490 m/s) and in the prism (cP=2670 m/s) the respective Doppler-angle can be calculated (law of refraction)
Basics:
Ultrasonic echography (A-image) order no GAMPT-10121 order no GAMPT-10131 order no GAMPT-10132 order no GAMPT-10201
Procedure:
The Doppler-effect is applied in the medical diagnostics for the investigation of running movements and moving structures as in cardiologic diagnostics, arterial and venous blood vessels, brain blood circulation and postoperative blood vessel control.
Values calculated with formula (3):
Figure 3
Ultrasound B-scan
Setup:
(2)
Figure 1
Results: For the evaluation of the ultrasonic image one has to keep in mind that the lateral local assignment may be inaccurate because the cross section image was taken hand-guided. Of course the precise position of the tumor can be palpated. On the other hand the depth and size of the tumor are determined only by the ultrasound image. The image of the breast model can be somewhat irritating, because the outer form of breast is imaged downwards. This echo is produced by the plain back side of the model and therefore the distance to the surface is imaged respectively. In the upper left area the tumor is recognizable that is only weakly reflecting. However the imaging of the sound shadow behind the tumor is more clear. The sound impedance of the tumor tissue is only slightly different from the surrounding tissue, however the attenuation is clearly higher. For the sound velocity of the Bimage intentionally the double velocity of water (3000 m/s) has been chosen in order to enhance the depth resolution in the presentation. All depth numbers must be divided into two. So the tumor exist in a depth of about 10 mm and has an extension of circa 20 mm.
Ultrasonic pulse Doppler „Flow-Dop“ order no GAMPT-50100 Ultrasonic probe 2 MHz order no GAMPT-10132 Doppler prism 3/8“ order no GAMPT-50112 Flexible tubes set order no GAMPT-50120 Centrifugal pump „Multi Flow“ order no GAMPT-50130 Doppler dummy fluid order no GAMPT-50140
If an ultrasound wave of frequency fo is hitting a moving object then this causes a shift of frequency due to the Dopplereffect. For a small velocity of movement of the object v in comparison with the sound velocity c in the medium equation (1) applies:
Procedure: First of all the breast model is examined by touching with fingers. In this way both tumors can be found and the position can be determined roughly. By the 1 MHz probe an echogram of the breast is taken in the fixed region of examination. For this it is necessary to choose the device parameter so that besides the echo from the bottom mainly the echo of the tumor is measured. The adjustments and the alignment of the probe demand some experience from the student. After choosing suitable adjustments a B-image of the breast model is taken along a chosen line. If the adjustment of amplification especially of the TGC and the movement of probe is well done a ultrasonic brightness image of the tumor is clearly visible.
The mamma tumor is the most common malignant alteration of the female breast. Besides the mammography (X-ray investigation) the mamma sonography is the most important examination for diagnosis. The sonography is applied in the early diagnosis of breast cancer. Its strong point lies especially in the distinction between liquid filled cavities (cysts) or alteration of tissue. By means of this method also aiming biopsy from the breast are carried out. Immediately before the operation the ultrasound investigation can show the precise position of the alteration and facilitate the surgeon an operation to the point. Especially after a cancer operation the remaining tissue can be better controlled by means of mamma sonography. Scar
Results:
Purpose:
Procedure:
Basics:
HF = heart frequency.
Distance of the pulses [mm]: 12, 12, 12, 12, 13, 11, 12, 13 ESD (max. distance between pulse and zero line [mm]: 21, 22, 21, 19, 20, 22, 20, 21, 22
order no GAMPT-10121 order no GAMPT-10131 order no GAMPT-10221 order no GAMPT-70200
tissue or the changed tissue density distort the image of the mammography. The mamma sonography complements so the mammography. For young patients the mamma sonography can be sufficient without mammography. An experienced physician using a advanced device detects knots in the breast up about 0.1 cm size. After recent investigations detection rate in comparison to mammography nearly the same. In big and dense breasts ultrasound is the better method of detection of knots. If mamma sonography is applied additionally to mammography the detection rate improves by circa 30 per cent.
Basics:
The dependencies of the ultrasound-Doppler-effect on the velocity of flow and the Doppler-angle is investigated.
The pump is switched on and the speed is adjusted in a middle range (ca. 4000min-1). The mode is GK (continuously, venous). With the Doppler probe and coupling gel the arm model is scanned for a vessel with a significant audio signal. The flow in the spectral image is analyzed for negative and positive components. The probe direction is switched 180°. Then the vessel is scanned for changes in the spectral image (Stenosis) and the differences between the images of the „healthy“ vessel and the stenosis will be characterized. Lastly the pump is switched to P1 and P2 mode (pulsatil) the images are analyzed and the pulse rate is determined.
Setup: Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Breast dummy with tumor Ultrasonic gel
From the recorded M-mode image first the mean heart frequency is determined over some heart cycles. For this the time distances of two heart cycles are measured and the average is calculated: time scale: 1s = 12 mm mean: 12,12 mm pulse duration: $T = 12,12 mm/12 mm s-1 = 1,01 s heart frequency: HF = 1/$T = 0,989 Hz
Ultrasonic Doppler effect order no GAMPT-10121 order no GAMPT-10134 order no GAMPT-10220
HZV = (EDS-EDV) * HF
Procedure: After filling the heart model with water the probe shall be fixed at a tripod in such a way, that the echo of the membrane appears at a sufficient distance to the impingement surface. Since in water the attenuation of the ultrasound wave is negligible the measurements can be performed without use of the TGC. The software parameter „sound velocity” is adjusted to water (1480 m/s). After that one switches in the software to the M-mode. By periodically compressing the rubber ball the rubber membrane simulates the heart wall motion. The periodical motion of the membrane is recorded in the M-mode and can then printed.
For all heart cycles the end-systolic diameter ESD (distance of the maximum of the curve from state of inactivity) of the heart model is determined. ESD = 20,89 mm
essential in many areas such as determining reverse blood flow in the liver vasculature in portal hypertension. The Doppler information is displayed graphically using spectral Doppler, or as an image using colour Doppler.
Doppler sonography use the Doppler effect to assess whether structures (usually blood) are moving towards or away from the ultrasound probe, and its relative velocity. By calculating the frequency shift of a particular sample volume, for example a jet of blood flow over a heart valve, speed and direction of this sample volume can be determined and visualised. Doppler frequency shift is the difference in ultrasonic frequency between transmitted and received echoes, i.e. the echo frequency minus the transmitted frequency. The Doppler frequency is proportional to the blood flow velocity. Doppler sonography is particularly useful in cardiovascular studies (sonography of the vasculature system and heart) and
Basics: In the echo cardiography a special ultrasound method is applied for the investigation of the heart movements. The timemotion-mode, called also TM- or short M-mode, is indicated particularly as one dimensional technique but shows still two dimensions: one spatial dimension (superimposed interfaces or structures) and one temporal dimension (changes of the structures in the systole and diastole). By means of the TMmode the motion of heart structures (cardiac wall, septum or cardiac valve and vessel valve) are displayed as picture points of different brightness. This form of recording yields an anatomically unusual image. For the determination of cardiac extensions, e.g. of cardiac walls and cardiac cavity diameter, the TM-mode is the investigation technique of choice. But also the judgment of the opening of heart and vessel valves is a domain of the TM-mode. For image recording first a appropriated region of the heart is chosen in the B-image (e.g. the long heart axis), then the M-mode is activated and the motion of
The end-diastolic volume is taken as zero in this model case. So that the heart time volume can be calculated. HZV = ESV * HF = 10,9 ml/s
Doppler sonography Purpose:
Purpose: In this experiment a typical application of ultrasound in medical diagnostics is given. At a realistic breast model a not-malignant tumor is diagnosed and by means of the brightness scan imaging method it is localized and measured.
Heart Systole
The heart volume is obtained under the assumption of a cone as model volume ( V = 1/12 * P * D² * h) with a diameter of 45 mm: From that follows: ESV = 1/12 * P * D² * ESD = 11,07 cm³ = 11,07 ml
echo of the double hole with the 4 MHz probe
The goal of the experiment is to learn how blood flow measurements with Doppler ultrasound works. A realistic arm model is used to show the differences between continuously (venous) and pulsatile (arterial) flow and between normal blood flow and a stenosis.
order no GAMPT-10121 order no GAMPT-10134 order no GAMPT-10220
the cardiac wall and the valves are recorded. From the changes of the cardiac wall distances and of the cavity area in the B-image the cardiac output can be calculated. From the measurement of the end-diastolic and the end-systolic ventricular diameter (distance of the cardiac walls) the corresponding heart volumes EDV (end-diastolic volume) and ESV (end-systolic volume) are determined. From this the heart time volume comes out via:
where tO is the measured time of flight without the sample (the path length s is constant).
Procedure:
The methods of investigation with ultrasound systems are based on the exact correlation of the information of a point in the region of examination to a recorded ultrasound echo. The smallest distance of two points the echoes of which can be just resolved is called the resolution power. The length of the sound pulse limits the axial resolution whereas the lateral resolution power is limited by the geometry of the sound field of the probe. Both effects depend strongly on the frequency. With increasing frequency the sound pulses become shorter so that the axial resolution power increases. However the depth of penetration decreases with increasing frequency.
Ultrasonic investigation with the breast dummy
Purpose: Using a simple heart model the wall motion is recorded by means of the ultrasonic time-motion method (M-mode). From the M-mode recording the heart frequency and the heart volume (HZV) are determined,
The sound velocity of the acrylic block was estimated with 2680 m/s. With the compound scan the test block can shown with high image quality. The biggest problem for the lateral resolution are movement artefacts, because the probe is moved by hand. The illustration of the upper 5 holes in the oblique group (hole diameter = 3 mm) shows the third hole with the best lateral resolution. The reason for this is the used 1 MHz probe has the focus zone ca 2.5 cm (focus distance of a round sound generator : x = R² /l, radius R=8 mm, wavelength l = 2.7 mm) The brightly ground echo is discontinued with dark ranges, because the holes above produce acoustic shadows. Especially in the range under the big hole on the right sight no measurements are possible, because there is no sound in it.
Results: Measured: length s= 150 +/-0,1 mm, time of flight t = 112,1 +/-0,3 µs, Calculated velocity of sound c = 2976 +/- 9m/s From determined distances calculated hole sizes in comparison to the actual hole sizes (all given in mm). Hole 1 and 2 cannot be separated by the 1 MHz probe. Hole 10 can be measured only from one side (acoustic shadow of hole 11). hole nr. echo S1 echo S2 hole size caliper
back 80,1
1/2 18,6 60,0
80,0
1,5
3 61,4 14,2 4,5 6,0
4 53,9 22,3 3,9 5,0
5 46,6 30,6 2,9 4,0
6 39,1 39,5 1,5 3,0
7 31,0 47,2 1,9 3,0
8 23,3 55,2 1,6 3,0
9 15,2 63,3 1,6 3,0
10 7,9 3,0
11 55,5 15,9 8,7 10,0
Figure 4
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Ultrasonic experiments
Ultrasonic Doppler methods Ultrasonic pulse Doppler “FlowDop” The pulse Doppler device generates pulses of transmission with a frequency of 2 MHz which are send as ultrasonic waves by a connected transducer. If these waves are scattered or reflected at moved particles or bubbles they suffer a frequency shift (Doppler effect). The device registers and evaluates these scattered waves. An audio signal is created. The audible volume is a measure of the amplitude of the reflected signal, the frequency is a measure of the speed of the scatterer. Simultaneously the amplitude is indicated as a deflection of a LED bar. Moreover the device can pass on the measured data to a PC in order to perform records and evaluations in detail. Sensitivity and volume can be adjusted on the device by means of control knobs. Technical data: Frequency Amplification Visualization PC connection Size Main voltage Power of electricity
2 MHz 10 - 40 dB LED-bar, acoustical signal volume controlled USB (parallel on request) 256 x 185 x 160 mm 90-230 V, 50/60 Hz 100 VA
By means of the supplied software “DopView” the data measured by the device can be evaluated on a PC/laptop. The connection to the device is realised via a USB interface. During the measurement the software shows the current Doppler signal. The evaluation uses a transformation into the frequency space by means of a Fourier-transformation. In this way the most frequent occurring or the highest occurring frequencies are determined which are a measure of the speed in the stream. These frequencies and the there out calculated velocities and flow values are displayed on the screen as values or as time curves, respectively. Additionally the energy content of the signal is displayed. Further evaluation functions are the representation of the spectrum with color-coded intensities over the time range or the examination of the pulsatility of the flow. By varying the sample volumes information from different layers of the stream can be obtained. In this way the velocity and concentration profile can be built. Experiments: PHY13 PHY14 PHY15
Ultrasonic Doppler effect Flow profiles Fluid mechanics
IND05 MED03
Flow measurement Doppler sonography
Order no: 50100
Doppler prism The Doppler prism serves as a connector between the ultrasonic probe and the tube. With this construction it is easy to contact the tube. On the other hand the three plane surfaces of the prism guarantee a good coupling to the probe. The size of the frequency shift depends essentially on the angle between incidence sound wave and streaming direction. The Doppler prism enables three different incidence angles and helps to demonstrate the dependence of the frequency shift on the Doppler angle. Technical data: Material Adaptation to flexible tubes Incident angle Doppler angle Approach distance Size
acrylic 1/2“, 3/8”, 1/4“ 15°, 30°, 60° ~8.8°, ~15.3°, ~28.8° 30 mm 60 x 40 x 25 mm
Experiments: PHY13 Ultrasonic Doppler effect PHY14 Flow profiles
PHY15 IND05
Fluid mechanics Flow measurement
Order no: 50111 (1/2“ tube) Order no: 50112 (3/8“ tube) Order no: 50113 (1/4“ tube) 28 Ultrasonic experiments
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Ultrasonic Doppler methods Set flow pipes and Doppler prisms For the investigation of flow phenomena there are pipes with three different inner diameters. The connectors are designed for 3/8” tubes. By means of the Doppler prism for the coupling to the pipe velocity or profiles of the stream can be measured. The advantage of pipes compared to flexible tubes is that no tripod materials are needed. Furthermore in a straight pipe develop rather laminar stream conditions. The stream pipes can be combined with riser pipes for pressure measurements and the centrifugal pump. A lot of interesting experiments can be realised in the field of flow phenomena with these pipes and prisms. Technical data: Material Length Inner diameter Connectors to
acrylic 300 mm 1/2“ (~ 15 mm), 3/8” (~ 10 mm), 1/4“ (~ 7 mm) 3/8” (~ 10 mm)
Experiments: PHY15
Fluid mechanics
Order no: 50201 (set)
Replacements: Order no: 50151-3 (flow pipes) Order no: 50111-3 (Doppler prisms) Order no: 50121 (tubes) Order no: 50122 (connectors)
Standpipe for pressure measurement To investigate the law of Hagen-Poiseuille or the Bernoulli equation it is necessary to measure the pressure conditions along a stream. A simple but very illustrative way is to use riser pipes. The pressure decrease along a tube is optically shown in the decrease of the filling level in the riser pipes. The scale has four riser pipes, which can be connected by means of the provided flexible tubes and Luer-Look connectors to 3/8” tubes. The connectors can be built in the circuit at the measuring points. By using 3-way-taps more than 4 measuring points are possible. The scale is divided in centimeter and millimeter, so arbitrary fluids can be used. The conversion to according pressures has to be done by the students. Technical data: Material acrylic Length pipes 1000 mm Connectors Luer-Look, male Length flexible tubes 1200 mm, Tube connectors 3/8” with Luer-Look, female (Delivered without tripod)
Experiments: PHY15
Fluid mechanics
Order no: 50150
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Ultrasonic experiments
Ultrasonic Doppler methods Flexible tubes set The acoustical properties are important for the choice of the selected tubes, e.g. if the tube material is too soft, not enough sound can be coupled into the tube to receive measurable data. We have tested the here offered tubes, among others these are used in medicine. By building a circuit with different tube diameters, different pressure and velocity conditions can be created in the circuit. These can be demonstrated clearly by different measuring methods (Doppler -> velocity, riser pipe -> pressure). The flexible tubes are easy to replace and there is no risk of fraction and injury. Technical data: Flexible tubes
1 m with 1/2“ and 1/4“, 3 m with 3/8”, various connectors, 3 way-taps
Experiments: PHY13 Ultrasonic Doppler effect PHY14 Flow profiles
IND05
Flow measurement
Order no: 50120
Centrifugal pump “MultiFlow” To investigate flow phenomena a laminar flow is essential. Therefore a centrifugal pump is a good choice. In contradiction to roller or gear pumps, centrifugal pumps enable a constant controllable flow rate. The pump head has connectors to 3/8´´ tubes. The fluid is completely separated from the drive module. The flow rate can be adjusted constantly and is infinitely variable in a range up to 10 l/min. To generate pulsatile flow rates (e.g. for Doppler examination) the pump can be regulated periodically. Technical data: Connectors Pump power Visualization Main voltage
3/8” max 10 l/min, adjustable Voltage, LCD-display, 90-230 V, 50/60 Hz
Experiments: PHY13 PHY14
Ultrasonic Doppler effect Flow profiles
PHY15 IND05 MED03
Fluid mechanics Flow measurement Doppler Sonography
Order no: 50130
Doppler dummy fluid For the measurement of ultrasonic Doppler signals scattering particles are needed in the fluid. These have to match in size and acoustic impedance to the used ultrasonic frequency. The offered dummy fluid contains encapsulated micro bubbles with excellent scattering properties. Technical data: Dummy fluid in plastic bottle, 1 l Ultrasonic scattering 1-6 MHz
Experiments: PHY13 Ultrasonic Doppler effect PHY14 Flow profiles
PHY15 IND05
Fluid mechanics Flow measurement
Order no: 50140 30 Ultrasonic experiments
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Ultrasonic Doppler methods Arm dummy with stenosis This very realistic model of a human arm gives medical students an introduction in the methods of ultrasonic Doppler diagnostics. These methods require a high level of knowledge about the Doppler sonography and their results. With the arm model it is possible to show all the basic principles of these diagnostic methods. The model contains several vessels and one stenosis. Together with the MultiFlow pump and the ultrasonic device FlowDop a high number of experiments can be realised. In the experiments the students can measure the typical spectra of continuous and pulsed flow. With the measured curves the flow index, the pulse-index and the resistanceindex are calculable. Additional measurements are the maximum and the mean flow and the profile of the flow. In the area of the stenosis the positive and negative flow components before and behind the seal of vessel are detectable. Technical data: Skin of silicone Body of uretane Silicone tubes with 1 stenosis Experiments: MED03
Doppler Sonography
Order no: 50160 (set)
Replacements: Order no: 50161 (dummy fluid arm)
Ultrasonic Doppler probe The ultrasonic Doppler probe with a frequency of 2 MHz is designed especially for measurements with the arm dummy. The pencil form and the small probe area result in a good handling and an adequate local resolution. The delay line with a determined angle of 30째 is responsible for a constant Doppler angle and a significant Doppler frequency shift. In this way a quantitative analysis to determine the flow velocity is possible. Technical data: Frequency 2 MHz Size: L= 200 mm, D= 15mm Cable 1 m Special plug connector for connection to FlowDop
Experiments: MED03
Doppler Sonography
Order no: 50135
Ultrasonic coupling gel For the acoustic coupling of ultrasonic probes to samples a coupling medium must be used. For this various oils and first of all water are utilised. For lab course the use of ultrasonic gel from medical diagnostics is recommended. These gels have a high viscosity but do not contain any oily components (there is no danger of contamination). The ultrasonic gel is water-soluble, skin-friendly and not poisonous. Technical data: Water-soluble, hypo allergenic Bottle with ultrasonic gel 250 ml
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Ultrasonic experiments
Ultrasonic scanning methods Computerised Tomography scanner (CT-scanner) Computerised tomography is an important method to investigate inner structures not only in medical diagnostics but also for testing materials. Thereby the principles of the generation of tomographic images are independent of the measuring method. Beside the well known procedures X-ray or NMR (nucleus magnetic resonance) also other measurement readings like positron emission tomography or ultrasonic tomography will be recorded. Our CT-scanner realises the rotation and the linear shift of a sample piece, which is the precondition for the calculation of tomographic images. In connection with the CT-control unit and the ultrasonic device GAMPT-Scan one can built a computer tomograph which is very versatile. The scanner has a sample holder for the interesting objects. This sample holder will be rotated exactly with a stepper motor. A second stepper can realise a linear shift with a local resolution < 10 µm. The sample holder will dip into a water filled tank. On the outside of this tank two ultrasonic probes are localised in opposition. During the measurement the holder will be moved between the probes corresponding to the ct-algorithm. The whole holder can be moved vertically, in this way the interesting area of the sample is adaptable. Furthermore the scanner enables a series of experiments to illustrate the generation of cross section images. Therefore a GAMPT ultrasonic probe (1,2 or 4 MHz) is attached to the sample holder. The sample object (e.g. test block or breast dummy) is placed into the bath and then scanned with assistance of the scanner control unit. The scanner can be controlled manually or with the delivered software. The recorded B-scans are free of motion artifacts and have a high local resolution, the quality can be improved by increasing the measurement time. Technical data: Linear movement Rotation Size
~400 mm, resolution <10 µm speed maximal 18 cm/min 360°, resolution 0.225° speed maximal 1 rotation/s 500 x 400 x 200 mm
Experiments: PHY09 PHY10
Ultrasonic computer tomography Characteristic of sound field
Order no: 60100 (set)
PHY16
Mechanical scan methods
Replacements: Order no: 60124 (sample holder)
CT-control unit with software The control unit for the CT-scanner can be connected to a serial interface of a PC or laptop. Together with the ultrasonic device GAMPT-Scan and the tomography software USCTView one receives an efficient computer tomograph and B-scan scanner. Using a micro controller 3 stepper motors can be controlled (rotate, linear shift and possibly a second linear direction). With PC and electronic the moving velocity of the scanner can be adjusted, the limit switches are observed and the positioning of the sample holder can be controlled. With push buttons, one for positive and one for negative direction, each stepper motor is controlled manually. Technical data: Output 3 x stepper motor control, bipolar, 5 V, max 2 A 6 x limit switches Interface PC serial, COM 1-4 Size 250 x 180 x 170 mm Main voltage 90-230 V, 50/60 Hz Power of electricity < 50 VA Software With the software USCTView it is possible to regulate the scanner control unit (60110) and to record data via the GAMPT-Scan (10121). Scanned B-scans as well as tomography images can be generated. The complete ct algorithm including different filter functions (non filter, rectangle, Ramachandran & Lakshminarayanan und Shepp & Logan) is integrated as well as all features for the signal representation known from the A-scan software. The current amplitude scan, the adjustments of time gain control tgc and amplifier, position [mm] and rotation angle [°] of the scanner are displayed. After each A-scan the tomography image will be updated and
32 Ultrasonic experiments
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Ultrasonic scanning methods built up step by step, so the student can understand and follow the generation of tomography images in detail. The ct- or B-scans can be exported or printed. Number and size of the steps in linear positioning as well as angle rotation are variable.
Experiments: PHY09 PHY10
Ultrasonic computer tomography Characteristic of sound field
PHY16
Mechanical scan methods
Order no: 60110
Water tank The water tank is made of thin Plexiglas plates. Therewith good acoustic coupling properties between the bath walls and the ultrasonic probes are guaranteed. The differences for the acoustic impedance between Plexiglas and water are relatively small (in comparison to glass), in this way reflections can be widely avoided. Technical data: Size Thickness
430 x 150 x 150 mm 4 mm
Experiments: PHY09 PHY10
Ultrasonic computer tomography Characteristic of sound field
PHY16
Mechanical scan methods
Order no: 60120
CT sample In the ultrasonic tomography two measuring values can be recorded, absorption and sound velocity. The sample is a black synthetic cylinder with inhomogenities inside. Technical data: Diameter Height
40 mm 60 mm
Experiments: PHY09
Ultrasonic computer tomography
Order no: 60121
Hydrophone holder The hydrophone holder helps to adapt the hydrophone to the CT sample holder (Order no: 60124 ) So the hydrophone can be easily used with the CT scanner for sound field measurements. (The holder is also used in the hydrophone set to adapt the hydrophone to the hydrophone plate). Technical data: Diameter 25 mm Height 25 mm
Experiments: PHY10 PHY19 PHY20
Characteristic of sound field Phase and group velocity Determination of the focus zone
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Ultrasonic experiments
The following examples of laboratory experiments can be classified into three sectionheadings:
• PHY (Physics) includes the basics of generation, expansion and interaction of ultra sound and the principles of ultrasonic methods
• MED (Medicine) includes examples of experiments with medical applications and • IND (Industry) contains selected industrial applications of ultrasound and the topic of non-destructive testing.
The individual experiments are presented under the following headings:
• PURPOSE describes the learning objectives of the experimental set, including the knowledge, skills and understanding a student would expect to gain
• BASICS gives a short theoretical introduction to the topic and related applications • SET UP lists all the equipment required with order-numbers and includes a photo graph of the experiment
• PROCEDURE explains the experimental method, measurements taken and pos sible sources of error
• RESULTS are arranged as tables or graphs. Some short explanations and interrelations of the results can be found there.
The experimental instructions are updated and extended permanently and can be downloaded under www.gampt.de.
34 Ultrasonic experiments
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Puls - Echo Laboratory Ultraschallverfahren experiments Accessories Content Experiments
34-67
PHY01
Ultrasonic echography (A-Scan)
36
PHY02
Velocity of ultrasound in solid state materials
37
PHY03
Attenuation of ultrasound in solid state materials
38
PHY04
Attenuation of ultrasound in liquids
39
PHY05
Spectral investigations
40
PHY06
Frequency dependence of resolution power
41
PHY07
Shear waves in solid state materials
42
PHY08
Ultrasonic B-Scan
43
PHY09
Ultrasonic computer tomography
44
PHY10
Characteristic of the sound field
45
PHY11
Debye-Sears effect
46
PHY12
Projection of standing waves
47
PHY13
Ultrasonic Doppler effect
48
PHY14
Flow profiles
49
PHY15
Mechanics of flow
50
PHY16
Mechanical scan methods
51
PHY17
Sound velocity in water, acoustic lattice
52
PHY18
Phase shift on the acoustic lattice
53
PHY19
Phase and group velocity
54
PHY20
Determination of the focus zone
55
IND01
Non Destructive Testing
56
IND02
Rayleigh waves
57
IND03
Level measurement
58
IND04
Concentration measurement
59
IND05
Flow measurement
60
IND06
Angle beam measurement
61
IND07
Time of flight diffraction technique (TOFD)
62
IND08
Detection of discontinuities
63
MED01
Ultrasonic TM-mode
64
MED02
Ultrasonic investigation with the breast dummy
65
MED03
Doppler sonography
66
MED04
Ultrasonic investigation with the eye dummy
67 35
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Ultrasonic experiments
PHY01
Ultrasonic echography (A-Scan)
Purpose:
Setup:
The relationship between time of flight of ultrasonic echoes, the velocity of sound and the distance between ultrasonic transducer and defect (reflector) for different size of defects is determined. Thus the velocity of the sound passing through the sample is calculated and the position and size of the defect is measured.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Ultrasonic test block transparent or black Ultrasonic gel
(1)
order order order order order
no no no no no
10121 10131 10201 10204 70200
s = c*t/2.
By knowing the velocity of sound of the material under investigation, the distance of a defect can be determined directly from the time of flight. The amplitude of the ultrasonic echo depends on the damping of the material between probe and defect, on the difference of the impedance of the material and defect as well as on the geometric form and orientation of the defect.
Procedure: The longest side of the sample (GAMPT-10201) is measured by a calliper or ruler. Then the ultrasonic transducer is coupled by a coupling gel to the sample and the echoscope is adjusted by variying the power of the transmitter, basic amplification and TGC so that the echo of the back is clearly visible. The time of flight up to the echo is measured and by using the edge length after (1) the velocity of sound of the material is determined. This is fed into the software and the display switched to â&#x20AC;&#x17E;depthâ&#x20AC;&#x153;. Now the distance to the defect can be measured directly. All defects of the sample are measured either relative to both long sides (so the extension of the defect can be determined) or are measured from two sides perpendicular to each other in order to find the precise position of the defect.
Basics: Using the ultrasonic echoscope an ultrasonic probe coupled to the medium under investigation is excited by a short pulse. The emitted ultrasonic wave is reflected at inhomogeneities of the sound impedance and this reflection is detected by the same transducer. The time of flight (t) between the start of pulse at the transmitter and the appearance of the echo is related to the velocity of sound (c) of the medium with the distance (s) of the defect from the ultrasonic probe in the following way:
Results: Measured: length s= 150 +/-0,1 mm, time of flight t = 112,1 +/-0,3 Âľs, Calculated velocity of sound c = 2976 +/- 9m/s From determined distances calculated hole sizes in comparison to the actual hole sizes (all given in mm). Hole 1 and 2 cannot be separated by the 1 MHz probe. Hole 10 can be measured only from one side (acoustic shadow of hole 11). hole nr. echo S1 echo S2 hole size caliper
back 80,1
1/2 18,6 60,0
80,0
1,5
3 61,4 14,2 4,5 6,0
4 53,9 22,3 3,9 5,0
5 46,6 30,6 2,9 4,0
6 39,1 39,5 1,5 3,0
7 31,0 47,2 1,9 3,0
8 23,3 55,2 1,6 3,0
9 15,2 63,3 1,6 3,0
10 7,9 3,0
11 55,5 15,9 8,7 10,0
36 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Velocity of ultrasound in solid state materials Purpose:
Setup:
The velocity of sound in acrylics shall be determined by time of flight technique with the echoscope. For this the measurement is done at three cylinders of different length in reflection as well as in transmission by ultrasound probes of different frequencies.
Ultrasonic echoscope GAMPT-Scan 2x ultrasonic probe 1 MHz 2x Ultrasonic probe 2 MHz Ultrasonic test cylinder set Ultrasonic gel
order order order order order
PHY02
no no no no no
10121 10131 10132 10207 70200
This error can be eliminated if the speed of sound is determined by a difference calculation from two measurements of different sample lengths: (3)
vP =(sP1-sP2)/(tP1+tAS-(tP2+tAS))=(sP1-sP2)/(tP1-tP2)
Procedure:
Basics: From the known distance (s) between the ultrasonic probe and the boundary of the solid and also the measured time of flight (t) the longitudinal velocity of sound (cl) can be determined for perpendicular incidence of sound in the following way: for measurements in reflection (1) cl = 2s/t for measurements in transmission (2) cl = s/t Since nearly all ultrasonic probes are produced with a protective layer on the active surface (ceramics) this causes an error in measurement of the velocity of sound because the time of flight is measured through this layer. That means the measured time of flight (tM) is built from the time of flight in the protective layer (tAS) and the time of flight in the sample (tP).
Results:
time of flight [µs]
values: cylinder 1: 40,2 mm cylinder 2: 79,8 mm cylinder 3: 119,2 mm
cylinder 1 cylinder 2 cylinder 3
1 MHz sP ∆sp tM ∆tM cP (1,2) ∆cP [mm] [mm] [µs] [µs] [m/s] [m/s] 40,2 0,1 15,7 0,2 2561 39 79,8 0,1 30,6 0,2 2608 20 80,4 0,2 30,8 0,2 2610 23 119,2 0,1 45,3 0,2 2631 14 159,6 0,2 60,6 0,2 2634 12 238,4 0,2 90,2 0,2 2643 8
cP (3) ∆cP [m/s] [m/s] 2658 2662 2669 2659 2660
85 90 43 30 13
The lengths of three different cylinders made from acrylics are measured. Then both the time of flight in reflection as well as in transmission are measured with a 1 MHz probe. This measurement is then repeated with a 2 MHz probe. The measurement of the time of flight is always done from the beginning of the transmitter pulse up to the beginning of the echo (received pulse). The velocity of sound is determined for each single measurement after the formula (1) and (2), respectively as well as for the differences referring to the smallest distance after (3). The determined velocities of sound are compared with each other and statements concerning errors in measurement, systematic errors and possible frequency dependencies are made.
1 MHz reflex. trans. 30,6 15,7 60,6 30,6 90,2 45,3
tM [µs] 15,5 30,4 30,6 45,1 60,4 90,0
2 MHz reflex. trans. 30,4 15,5 60,4 30,4 90,0 45,1
2 MHz ∆tM cP (1,2) ∆cP [µs] [m/s] [m/s] 0,2 2594 40 0,2 2625 21 0,2 2627 24 0,2 2643 14 0,2 2642 12 0,2 2649 8
cP (3) ∆cP [m/s] [m/s] 2658 2662 2669 2659 2660
85 90 43 30 13
The velocities of sound calculated after (1) and (2) show a systematic error, whose influence becomes smaller with increasing measuring length. This error is larger for 1 MHz than for 2 MHz (the protective layer is larger for 1 MHz). The after (3) calculated values show by their homogeneity that this error has been eliminated. The mean value is 2662 m/sec for 1 MHz and 2 MHz. Moreover it appears that the error caused by the protective layer is larger than the error in measurement of the measuring set up. A comparison of the measurements for 1 MHz and 2 MHz shows that in this frequency range a frequency dependence of the velocity of sound (dispersion) does not occur for acrylics. Literature value: longitudinal sound velocity of acrylics =2600-2800 m/s
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
PHY03
Attenuation of ultrasound in solid state materials
Purpose:
Setup:
The damping of ultrasound in solids shall be determined for 3 different frequencies in reflection as well as transmission and be compared with values from the literature. Moreover the frequency dependence of damping is dealt with.
Ultrasonic echoscope GAMPT-Scan 2x ultrasonic probe 1 MHz 2x ultrasonic probe 2 MHz 2x ultrasonic probe 4 MHz Ultrasonic test cylinder set Ultrasonic gel
order order order order order order
no no no no no no
10121 10131 10132 10134 10207 70200
account that the intensity (I) is proportional to the square of the amplitude (A²) and that the conversion into the commonly used unit dB/cm results in (2)
µ [1 / c m] bzw. [ Neper / c m] =
µ
Basics:
I
=
µ [ d B / c m] 8.686
A 2 * 8.686 Ln 2 ( x1 − x2 ) A1
Procedure:
A sound wave running through a medium loses energy at different processes (scattering, absorption, reflection). This is called attenuation. The intensity I of the wave obeys the attenuation law (1):
=
µ [ d B / c m] 2 0 L g (e)
= I 0 e−µ x
where (IO) is the initial intensity, (x) is the path length in the medium and (µ) is the attenuation coefficient. By measuring two samples of the same material but of different lengths the material specific attenuation coefficient (µ) can be determined by (2) that comes from (1) by rearrangement. Here is taken into
By means of a measuring cursor for the determination of amplitudes the amplitude (A) of the (a) back wall echo and the (b) transmission pulses is determined for three acrylic samples of different length. This is done for 1 MHz as well as for 2 and 4 MHz probes. The lengths of the samples are measured by a calliper. From the measured amplitudes the damping values are calculated after (2). Because of deviations in the characteristics of the probes only measurements of the same frequency and type of measurement (reflection or transmission) are in proportion. Moreover in all cases the adjustment of amplification must be identical.
Results: Measurement value cylinder 1: 40,2 mm cylinder 2: 79,8 mm cylinder 3: 119,2 mm 1 MHz s [mm]
A [mV]
40,2 832 79,8 315 119,2 125 80,4 702 159,6 103 238,4 23 mean SD
µ [dB/cm] 4,26 4,17 4,21 3,76 4,10 0,23
2 MHz A [mV] 928 272 73 872 69 8
4 MHz
µ [dB/cm]
A [mV]
µ [dB/cm]
4,90 5,35
829 102 14
9,19 8,97
5,09 4,92 5,07 0,21
9,08 0,15
The attenuation coefficients amount to 4,1 dB/cm for 1 MHz, 5,1 dB/cm for 2 MHz and 9,1 dB/cm for 4 MHz. That means that in acrylics the attenuation increases strongly with the increasing frequency. Measurements with 4 MHz in reflection are not possible anymore because the damping is too large to allow measuring of all lengths with comparable adjustments. The attenuation coefficients do not differ much for transmission and reflection, so that the influence of sound field does not play any role.
38 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Attenuation of ultrasound in liquids Purpose:
Setup:
The attenuation of sound in various liquids is measured depending on the layer thickness and is displayed graphically. By linear regression and by means of the law of attenuation the attenuation coefficients are calculated for particular materials.
Ultrasonic echoscope GAMPT-Scan 2x ultrasonic probe 2 MHz Aluminium sample for shear wave Shear wave set Ultrasonic gel
order order order order order
PHY04
no no no no no
10121 10132 10213 10210 70200
In liquids the amplitudes of the reflected signal for different distances are determined easily by means of a movable reflector. The attenuation coefficient alpha is then calculated for two layer thicknesses x1/2 and x2/2 (for measurements in reflection the path length of sound is two times the layer thickness) after the following equation:
α
=
1 A Ln 2 ( x1 − x2 ) A1
The unit of the attenuation coefficient is in this case [1/cm] or [Neper/cm]. Generally the unit [dB/cm] is used for the attenuation coefficient for the sound intensities I ~A². With the conversion of the dB-scale: dB = 20 Lg (e) the attenuation coefficient alpha is calculated by:
Basics:
α [dB/cm] = 2 α [Neper/cm]* 8,686
During the extension in liquids the sound wave suffers an attenuation that is caused by a loss of energy (absorption), reflection, scattering and geometry of the sound field. For the total damping holds: DGes = DAbs DRef DStreu DGeo Reflection and scattering can be neglected for many liquids. The influence of the sound field geometry can be estimated by comparison within water (absorption is negligable at low frequencies). For the attenuation of the signal amplitude the general attenuation law holds:
A =
A0 e −αx
Procedure: First of all the velocity of sound in the liquid is determined in transmission. For this the sample vessel is transmitted once in longitudinal and then in cross-direction, the time of flight and distance of transducers are measured. From ratio of the differences the velocity of sound in the liquid is calculated. The values can be put into the program, so that the layer thickness can be determined directly from the measurements of times of flights. For the recording of the measuring curve it is advisable to carry out all measurements with the same adjustment of amplification. For each measurement the reflector has to be adjusted for maximum signal amplitude.
Results: With an external program the attenuation coefficient alpha can be determined in an easier way from a linear fit if the function
2∗ L n
A0 ∗ 8,686 Ai
water glycerine sun flower oil
= α ( xi − x0 )
is plotted corresponding to linear equation: y = a x + b. A0 is the amplitude of the first measurement from the sight of the ultrasound probe. All the following measurements (i) are related to this value, so that for large distances the error of measurements becomes smaller. The measurement in comparison with water does not show a measurable damping at the applied frequency of 2 MHz, so that the influence of the geometry of the sound field can be assumed negligible for these measurements.
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
PHY05
Spectral investigations
Purpose:
Setup:
Using a simple model of the multiple reflection at a plate the difference between a spectrum of a pulse and the spectrum of periodic signals is demonstrated. Moreover the cepstrum shall be built from a periodic spectrum and the length of period of the signal be determined from the spectrum as well as from the cepstrum. The length of period is proportional to the plate thickness. From the received length of period the particular plate thickness shall be determined.
Ultrasonic Ultrasonic Ultrasonic Ultrasonic
Basics: By means of Fourier transformation (FFT) it is possible to decompose a time variable signal into the frequency components contained within it. From the generated spectrum one derives additional properties of the object under investigation. The influence of a periodic excitation (here multiple reflections) manifests as spectral maxima at multiples of the fundamental frequency FO Thus as multiplicative superpositions of the fundamental spectrum of the probe with an undulation in form of equidistant maxima in the spectrum, the distance of which corresponds to the fundamental frequency FO. From the distance of maxima follows via TO = 1/FO the time of flight between the reflexes. By means of the so-called cepstrum method the spectrum can be smoothed and the length of the period TO be determined directly. The cepstrum arises by a FFT of the logarithmised spectrum. By logarithmis-
echoscope GAMPT-Scan probe 2 MHz test plates gel
order order order order
no no no no
10121 10132 10202 70200
ing the multiplicative superposition of the periodicity and the fundamental spectrum becomes an addition. If FO and the fundamental frequency are wide apart from each other (e.g. 200 kHz and 2 MHz), the now additive parts can be separated by a further FFT in the generated cepstrum. If a filter is applied in the cepstrum between the frequency parts the fundamental spectrum can be restored by an inverse Fourier transformation.
Procedure: The reflection signal generated at the combination of delay path (40 mm cylinder) and the plate is adjusted by means of TGC to nearly the same height for all reflexes. The distances of the multiple reflexes are measured, then a spectrum of the first reflex, and respectively a spectrum and cepstrum (software function FFT) of the whole time range of the multiple reflexes are built. From that the mean frequency distance and the first peak in the cepstrum is measured, resp. in order to determine the time of flight of one reflex. With the known velocity of sound of the plate (2670 m/sec) the thickness is calculated.
Results: The echo image shows the first reflex at the transition of the delay path to the reflection plate. The multiple reflexes appear inside the plate. If one measures the distances between the particular multiple reflexes, one obtains 6,9 µs resp. and with a velocity of sound of 2670 m/s a thickness of 9,2 mm. A FFT over the first reflex at the plate yields the spectrum of the probe (Fig. 1) with a maximum at 2 MHz. A FFT over the three multiple reflexes in the plate gives a spectrum (Fig. 2) in which the parts of the probe and the periodic parts of the reflections at the plate are superimposed. If one determines the distance between the maxima one obtains a mean difference of frequency of 144 kHz. This corresponds to a time of flight of 6.95 µs, which gives a plate thickness of 9,3 mm. Creating (from this spectrum) the cepstrum (Fig. 3) from the first maximum a periodic time of flight of 6,9 µs can be read directly. In this way the spectral evaluation methods provide further possibilities for thickness measurements and the determination of scattering distances for small periodic structures.
40 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Frequency dependence of resolution power Purpose:
Setup:
By means of two neighbouring defects the different axial resolution power of a 1 MHz and a 4 MHz ultrasonic probe is examined. Thus the relationship between wavelength, frequency, pulse length and resolution power is illustrated.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Ultrasonic probe 4 MHz Ultrasonic test block transparent or black Ultrasonic gel
order order order order order order
PHY06
no no no no no no
10121 10131 10134 10201 10204 70200
Procedure: First of all the frequency of the probe is determined at a slightly damped echo. For this the echo of a localised defect near the surface is examined at a test block. By adjusting the power of the transmitter and receiver and the TGC a suitable RF-signal is adjusted. With both measuring lines the pulse length and the distance are measured for a number of oscillations in the time range and from this the frequency is calculated. It is recommended to use the zoom function for the 4 MHz probe. Then consequently the double defect of the test block is investigated with the 1 MHz and 4 MHz probe respectively. In the echogram the distance of both defects is measured.
Basics: The methods of investigation with ultrasonic systems are based on the exact correlation of the information about a point in the region of examination to a recorded ultrasonic echo. The smallest distance between two points whose echoes can be just resolved is called the resolution power. The length of the sound pulse limits the axial resolution whereas the lateral resolution power is limited by the geometry of the sound field of the probe. Both effects depend strongly on the frequency. With increasing frequency the sound pulses become shorter so that the axial resolution power increases. However the depth of penetration decreases with increasing frequency.
Results: The determination of the frequency of probes from the echo in the time range shows deviations from the nominal frequency: 1 MHz: T = 4,7 µs / 5 periods f= 1,06 MHz 4 MHz: T = 1,3 µs / 5 periods f= 3,85 MHz These deviations are caused by the frequency dependent damping, the large bandwidth of a pulse probe and the relative large error in measurement at the time limited resolution of the echoes. The determination of the pulse length shows distinctly longer pulses for lower ultrasound frequency. Pulse length: 1 MHz 10 µs 4 MHz 3 µs During the investigation of the double defect it appeared that the holes could not be resolved by the 1 MHz probe. There is only one peak for both holes. The echogram using 4 MHz shows two distinctly separated peaks. The time distance of the peaks was determined to 1.3 µs. With a velocity of sound of 2680 m/s the hole distance amounts to 1,7 mm. (Control measurements by the calliper: 1.6 mm)
echo of the 1 MHz probe
echo of the 4 MHz probe
echo of the double hole with the 1 MHz probe
echo of the double hole with the 4 MHz probe
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
PHY07
Shear waves in solid state materials
Purpose:
Setup:
Using sound transmission through a parallel plate at different angles the origin and transmission of longitudinal and shear sound waves are shown in solids. From the relationship between amplitude and angle the longitudinal and shear velocity of sound of the plate material is determined and from that the elastic coefficients of the material are found.
Ultrasonic echoscope GAMPT-Scan 2x ultrasonic probe 1 MHz Shear wave set Aluminum sample for shear waves Ultrasonic gel
order order order order order
no no no no no
10121 10131 10210 10213 70200
(this applies analogously for the total reflection of the shear wave). From the velocities of sound cT and cL knowing the density of the material the elastic coefficient µ (Poisson number), the elasticity module E and the shear module G are determined by:
cL 2 (1 − µ) = (3) cT 1 − 2µ
(5)
cL
=
(4)
cT
=
G ρ
E 1− µ ρ (1 + µ ) (1 − 2 µ )
Procedure:
Basics: At oblique incidence of an ultrasonic wave from a liquid at a solid longitudinal as well as shear sound waves are excited in the solid. Since the transmission of the shear wave through the plate is maximal at an angle of 45° from the maximum of the shear amplitude curve this incident angle φ is determined and by that the shear velocity of sound is calculated by (1) (1)
cT
=
1/ 2 cF sin(φ)
(cF is velocity of sound in the liquid). From the angle of first total disappearance of the longitudinal wave (total reflection) the longitudinal velocity of sound is determined after (2) (2)
cL
=
1 cF sin(φ)
Using two different materials (acrylics, density = 1,2 g/cm³ aluminum, density = 2,7 g/cm³ ) the transmission amplitudes of the longitudinal and shear sound waves are measured for different angles of incidence in very small steps (2,5°), starting at perpendicular incidence up to angles with vanishing signals. Since the sound velocity of the shear wave is distinctly smaller than that of the longitudinal wave the echoes can be separated quite easily because of the difference in time of flights. The following ranges can be distinguished (as example acrylics): 1. angle of incidence 0°, only the peak of longitudinal sound wave exists with possible multiple reflexes (no shear forces); 2. small angle (<=10°), multiple reflexes disappear, longitudinal amplitude becomes smaller; 3. angle range between 10 - 30°, peaks of longitudinal as well as shear waves exist; 4. angle range > 30°, only shear wave exists with decreasing amplitude at increasing angle. For other materials the situation is similar at other angles. The measured amplitudes are plotted versus the incidence angle from the normal. From the angle of total reflection of the longitudinal wave and the angle of maximal amplitude of the shear wave the velocities of sound are determined after (2) and (1) and the elastic coefficients are calculated after (3) and (5), the results are compared with values from the literature.
Results: The following values of angles φ can be read from the measured numbers or be determined by means of interpolation (angle of maximum) or extrapolation (angle of total reflection) and from these the velocities of sound are calculated by (1) and (2) ( velocity of sound in water = 1480 m/s): maximum total reflection total reflection shear shear longitudinal material
φ[°]
vT [m/s]
φ[°]
vT [m/s]
φ[°]
vL [m/s]
acrylic
41
1595
86
1484
33
2717
aluminium
17
3579
29
3053
13
6579
By comparison with values from the literature (aluminium vL=6320-6420 m/s, vT=3040-3160 m/s), we find in this case that the plate is not pure aluminum but an alloy. For acrylics (vL=2610-2780 m/s, vT=1430-1450 m/s) shows that the determination from the maximum angle gives too large values. For this, effects of damping and geometry can play a role. Therefore the calculation of the elastic coefficients by (3) to (5) the values determined from the total reflection were used. acrylic
aluminium
coefficient calculated literature calculated literature ρ [g/cm³]
1,2
2,7
υ
0,29
0,30
0,36
0,33
E [MPa]
6800
3300
69000
70000
G [MPa]
2600
1700
25000
26000
42 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Ultrasonic B-Scan Purpose:
Setup:
The basics of generation of ultrasonic B (Brightness) -scans are shown with a simple sample object. The the characteristics of image quality are explained, like focus zone, resolution power and artefacts.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Ultrasonic probe 2 MHz Ultrasonic test block transparent or black
order order order order order
PHY08
no no no no no
10121 10131 10132 10201 10204
Procedure: To generate a B-scan, first estimate the sound velocity of the acrylic block. Following this the test block will be measured using the Ascan with suitable adjustments for transmitter and receiver, so that the signal amplitudes from objects near the surface are not saturated. Important beyond everything else for this is the TGC. For the acoustic coupling of the ultrasonic probe the use of a water film is recommended as the ultrasonic gel has a strong static friction. Input the size and the sound velocity of the test block into the B-scan software. After starting the measurement move the probe with constant speed over the block. The dependence of the image quality can be shown by variation of the adjustments and the scan speed. Additionally the effect of the ultrasonic frequency on the lateral resolution can be shown by using a 2 MHz probe.
Basics: At the ultrasonic section image the echo amplitude is shown as a gray scale value (brightness -> B-scan) and the time of flight as penetration depth. The lining up of several adjacent A-scan lines results in the section image. For this the probe will be moved lengthwise over the area of interest, the local assignment alongside this movement is done with the position and the speed of the probe. A simple way to generate the B-scan is by slowly moving the probe by hand (compound scan). Thereby a precise lateral local power resolution is only possible with additional systems to get the coordinates (i.e. linear scanner). However, with the arbitrary slow scan speed it is possible to generate images with high quality in a wide area of interest. The image quality depends on the following parameters: -precise registration of the coordinates (scanner system) -axial power resolution (ultrasonic frequency) -lateral power resolution (ultrasonic frequency, geometry of the sound field) -gray scale resolution (transmission power, amplification, TGC) -number of scan lines (speed of probe movement) -aberrations (sound shadows, movement artefacts, multiple reflections)
Results: The sound velocity of the acrylic block was estimated with 2680 m/s. With the compound scan the test block can be shown with high image quality. The biggest problems with lateral resolution are movement artefacts, because the probe is moved by hand. The illustration of the upper 5 holes in the oblique group (hole diameter= 3 mm) shows the third hole with the best lateral resolution. The reason for this is that the 1 MHz probe has the focus zone ca 2.5 cm (focus distance of a round sound generator: x= R² /l, radius R= 8 mm, wavelength l= 2.7 mm) The brightly illuminated ground echo is discontinuous with dark ranges, because the holes above produce acoustic shadows. Especially in the range under the big hole on the right side no measurements are possible because there is no sound in it.
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
PHY09
Ultrasonic computer tomography
Purpose:
Setup:
The several steps of the formation of a computed tomography are illustrated. The difference between damping and sound velocity as measuring parameters is analysed. The influence of filtering and image processing is investigated.
Ultrasonic echoscope GAMPT-Scan Computerised Tomography Scanner CT control unit 2x ultrasonic probe 2 MHz CT sample Water tank Ultrasonic gel
order order order order order order order
no no no no no no no
10121 60100 60110 10132 60121 60120 70200
of flight is used as the measuring quantity and the following is valid: (2)
c∝
t0 t
where tO is the measured time of flight without the sample (the path length s is constant).
Procedure:
Basics: To form the image the attenuation of sound and the sound velocity are utilised. The attenuation coefficient of sound µ results from the measured amplitude A and the amplitude without sample A0 after the law of attenuation: µ ∝ Ln
(1)
The sample (damping or velocity sample) is attached to the sample holder and by means of the scanner control is positioned exactly between the two sensors. Then the sample holder is moved half of the scanning way, the accuracy of scanning and the number of angle intervals are adjusted and the CT scan is started. During the measurements the individual line scans are observed and the generation of the tomograms by superposition of the projections of line scans is studied. The resulting images are optimised by means of various filters and by brightness and contrast adjustments, then the damping tomogram is compared with the velocity tomogram.
A0 A
For the generation of the sound velocity tomogram the time
Results: The transmission signal (the diagram left above) has been measured with regard to maximal amplitude and time of flight of the maximal amplitude and from this a line profile (scan at one angle, 500 µm point distance) has been built (diagram left below). The superposition by means of the CT-algorithm (25 angle intervals) yields for sound attenuation to the image left above (non filtered, contrast changed) and for the sound velocity to the image right above (also non filtered, contrast changed). Filtering the attanuation image improves the contrast so the edges become visible (reflection losses). The inner part hardly distinguishes from the surrounding water, in the sound velocity image (right) the sample and the inclusion are clearly visible as homogeneous regions of a different sound velocity.
44 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Characteristic of sound field Purpose:
Setup:
The sound pressure amplitude of an ultrasonic probe (here 2 MHz) is determined along the sound field axis by means of a hydrophone and from the distribution of amplitudes the near field length is examined and compared with the theoretical value. Then the sound pressure amplitude is measured in the region of the near field and at two additional positions perpendicular to the sound direction, in order to get information about the sound field width.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Hydrophone Hydrophone holder Water tank Computerised Tomography Scanner CT control unit Ultrasonic gel
Basics: Ultrasound spreads out from the sound source into the neighbouring medium. The energy connected with the sound fills a region called the sound field. The sound field quantities (e.g. velocity of sound, sound pressure, sound intensity) indicate quantitatively the sound phenomenon within the spreading medium. The sound field, generated by a transducer in the medium, is classified into two regions, the near field or Fresnel zone and the far field or Fraunhofer zone. The pressure distribution shows in the near field strong position dependent fluctuations due to interferences. These fluctuations decrease continuously in the far field. For a piston oscillator the near field length (S) can be determined from the radius (a) of the probe and the wavelength (l) in the spreading medium: S=
a2 l
The near field length is defined as the last maximum on the acoustic axis. The theoretical sound pressure distribution on
order order order order order order order order
PHY10
no no no no no no no no
10121 10132 10250 60123 60120 60100 60110 70200
the transducer axis is represented for a continuous working transmitter with a diameter of 16 mm and a hydrophone with infinitesimal small surface (green curve) and for 2 mm radius (blue curve) in the following diagram. By the finite extent of the hydrophone the strong interferences in the near field range are smoothed. In the range of the near field length the sound field of the piston oscillator has a natural focus zone, i.e. the strongest lateral decrease of the amplitude.
Procedure: The probe with the support is coupled to the short side of the vessel and is adjusted perpendicular to the hydrophone. Then the hydrophone is moved into the far field region (ca 20 cm distance from the transducer) and their height adjusted for maximal amplitude. The hydrophone is positioned up to the vessel wall, the central positioning is checked and a scan is carried out along the axis of the transducer (ca 20 cm). From the last maximum the near field length is determined and compared with theoretical values. At the position of the near field length and at two further positions a scan perpendicular to the sound axis is carried out after having rotated the sample vessel by 90째. From the measured distributions the 6-dB-width (amplitude decrease to the half) is determined and is compared for the different positions.
Results: Fig. 1 shows the line scan along the sound field axis. The maximum comes up to about 95 mm distance of probe. The theoretical value after (1) is 86 mm for a probe with 16 mm diameter and 2 MHz frequency in water (c=1480 m/s). One observes from the theoretical calculation that the value from the hydrophone measurement is slightly shifted to the right. Furthermore one has to keep in mind that the measurement is done with a pulse transducer. This results in further decreasing interferences clearly visible in the measurement. The lateral sound field distributions are shown in Fig. 2 to 4, where the measurements have been carried out at probe distances of 27 mm (Fig. 2), 47 mm (Fig. 3) and 95 mm (Fig. 4). From the diagrams 6-dB-widths of 13 mm, 11 mm and 7 mm are determined. A distinct focussing in the range of the near field length can be observed.
Abbildung 2
Abbildung 3
Abbildung 1
Abbildung 4
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Ultrasonic experiments
PHY11
Debye-Sears effect
Purpose:
Setup:
The light diffraction at a progressing ultrasonic wave can be demonstrated (Debye-Sears effect). For this the dependence of the diffraction maxima on the wavelength of light (red and green) and on the frequency of the ultrasound will be investigated. From the geometry of the diffraction image the sound velocity of a test liquid (here distilled water and alcohol) is determined.
Ultrasonic wave generator SC500 Complete set Debye-Sears Laser module green Sample reservoir with laser support Tap for sample reservoir water, alcohol
order order order order order
no no no no no
20100 20200 20211 20225 20223
x between the -N th and +N th order of diffraction must be determined. From the known wavelength of the laser light lL the wavelength of the ultrasonic wave λS can then be calculated via (1). lS =
Basics:
(1)
In 1932 Debye and Sears showed for the first time that light crossing a liquid that is excited by a high frequency oscillation undergoes a diffraction. The density maxima and minima of a standing or continuously progressing wave act like lattice elements of an optical diffraction lattice. The lattice constant corresponds to the wavelength of the ultrasound and therefore depends on their frequency and the sound velocity of the medium. From the diffraction images of the Debye-Sears experiment the wavelength of the sound wave can be determined and with that the sound velocity in the liquid can be calculated. Therefore the distance s between the ultrasonic source and the diffraction image must be measured, the number N of diffraction maxima and the distance
Procedure:
2 N lL s x
The distance s between the ultrasonic transducer and the diffraction image is measured by a ruler. The maximum order of diffraction N is determined and the distance between the -Nth and the +Nth order of diffraction x is measured by a calliper or a ruler. The measuring is carried out for all frequencies in the range from 1 MHz on in 1MHz steps, as long as diffraction maxima are visible and separable. The measurement is performed for red as well as green laser light. From the measured values the wavelength of sound λS is determined after (1) and with the known frequency f the sound velocity c is obtained using c=f*λS. The measurement should be done also for the second liquid (e.g. alcohol).
Results: As expected from equation (1) with increasing ultrasonic frequency an increase of the distance of diffraction orders can be seen. When comparing the distances of diffraction orders for the same ultrasonic frequency but with different laser lights, red light gives larger distances. The number of diffraction orders is determined mainly by the transmission characteristics of the probe and the frequency attenuation. The main error results from measuring the distances of the diffraction orders x. This can be reduced applying a larger distance s or a suitable optical projection. The mean sound velocity of 1479 m/s lies near the theoretical value of 1482 m/s at 20 C.
f N [MHz] 1 2 3 4 5 6 7 8 9 10 11 12
5 4 3 2 2 2 2 2 2 1 1
x [cm]
x/(2N) [cm]
2,4 2,9 2,8 2,3 2,8 3,2 3,7 4,2 4,6 2,6 2,8
0,240 0,363 0,467 0,575 0,700 0,800 0,925 1,050 1,150 1,300 1,400
lS
c [m/s]
720,4 477,0 370,5 300,7 247,0 216,1 186,9 164,7 150,3 133,0 123,5 mean SD
1441 1431 1482 1503 1482 1513 1495 1482 1503 1463 1482 1479 26
green laser: λL=532 nm, s=325 cm f N [MHz] 1 2 3 4 5 6 7 8 9 10 11 12
9 5 5 3 3 2 2 2 2 1 1 1
x [cm]
x/(2N) [cm]
2,5 2,8 4,3 3,5 4,3 3,5 4 4,6 5,2 2,8 3,2 3,5
0,139 0,280 0,430 0,583 0,717 0,875 1,000 1,150 1,300 1,400 1,600 1,750
λS
c [m/s]
1525,7 756,8 492,8 363,3 295,7 242,2 211,9 184,3 163,0 151,4 132,4 121,1 mean SD
1526 1514 1478 1453 1478 1453 1483 1474 1467 1514 1457 1453 1479 26
red laser: λL=652 nm, s=325 cm
46 Ultrasonic experiments
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www.gampt.de
Projection of standing waves Purpose:
Setup:
Using divergent laser light the image of a standing ultrasonic wave can be demonstrated. By means of the originating projection image the dependence on the wavelength of light (red and green) and on the frequency of the ultrasonic wave is investigated. From the geometry of the projection image the velocity of sound of the test liquid (here distilled water) is determined.
Ultrasonic wave generator SC500 Complete set Debye-Sears Laser module green Projection lens Ultrasonic absorber
At exact alignment of the ultrasonic probe to the bottom of the vessel a standing wave arises. This can be displayed in transmission with divergent light because the sound pressure generates periodic changes of the refraction index. On the screen the density distribution of the standing wave will be shown as modulation of brightness. The distance of brightness maxima follows from x=
no no no no no
20100 20200 20211 20230 20227
The distance a1 between the sound field and the glass wall on the side of the lens can be taken approximately as half the inner dimension of the vessel minus half of the transducer diameter (a2 follows then from the inner dimension minus a1, N is the number of brightness maxima and x the belonging distance). The sound velocity of the medium c follows from the frequency f after (2) as c=ls*f.
Basics:
(1)
order order order order order
PHY12
Procedure: The projection lens is inserted into the laser support and by that into the optical path. The distance between the edge of the vessel and the diffraction image s is measured by a ruler. The number of brightness maxima N is determined and the distance x is measured by a calliper or a ruler. The measurement is done for all frequencies in the range from 1 MHz on in steps of 1 MHz, as long as a projection image can be observed. The measurement is carried out for red as well as for green laser light. From the results of measurement the wavelength of sound ls is determined after (1) and using the known frequency f the velocity of sound c is determined after (2). The values are compared for the different laser wavelengths and deviations to values from the literature discussed. With the ultrasonic absorber can be demonstrated that the standing waves and the projection image disappear but the diffraction stays (Debye-Sears effect).
lS f − a1 − g1 2 s − ( f − a1 − a 2 − g1 − g 2 )
For the exact determination of the wavelength from the image and the geometry the refraction corrections through the glass walls and the measuring liquid have to be considered beside the focal distance f of the lens in air (concerning the geometry see the following scheme). Furthermore one has to consider, that by using monochromatic light the focal distance of the lens f as well as the refraction index are functions of the wavelength of light. For the exact determination of the wavelength the method of light diffraction is recommended as described in the experiment of Debye-Sears effect.
Results: a1 = 4,05 cm a2 = 5,65 cm s = 280 cm g1= 4,9 mm g2 = 3,9 mm f = 10 cm (with 652 nm red laser) , red laser: λL=652 nm, s=325 cm sound velocity of water: 1482 m/s at 20°C f [MHz]
N
x [cm]
λS
c [m/s]
f [MHz]
N
x [cm]
λS
c [m/s]
2
2
4,1
793
1626
2
4
7,7
763
1527
3
3
4,0
529
1586
3
7
9,0
510
1530
4
4
4,0
407
1586
4
7
6,9
391
1564
mean
1573
red
mean
1540
green
Red laser: l =652 nm, Green laser: l=532 nm As expected from equation (1) the distance of brightness maxima decreases with increasing ultrasonic frequency. The determined sound velocity value is always too large and is larger for green light too. This error results from the change of the focal length of the lens due to transmission through the glass plates and the measuring liquid. The difference between green and red light is explained by the wavelength dependence of the refraction indices.
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
PHY13
Ultrasonic Doppler effect
Purpose:
Setup:
The dependencies of the ultrasonic Doppler effect on the velocity of flow and the Doppler angle are investigated.
Ultrasonic pulse Doppler „FlowDop“ Ultrasonic probe 2 MHz Doppler prism 3/8“ Flexible tubes set Centrifugal pump „MultiFlow“ Doppler dummy fluid Ultrasonic gel
order order order order order order order
no no no no no no no
50100 10132 50112 50120 50130 50140 70200
The applications of the Doppler effect in the medical diagnostics are at the investigation of running movements and moving structures as in cardiologic diagnostics, arterial and venous blood vessels, brain blood circulation and postoperative blood vessel control.
Procedure: The Doppler prism is attached to a 3/8“-tube as measuring distance. On the control of the centrifugal pump three different flow velocities (voltages) are adjusted and at each angle of the prism (aP= 15° , 30° and 60° ) the shift of Doppler frequency is determined for each velocity. From the known sound velocities in the liquid (cl=1490 m/s) and in the prism (cP=2670 m/s) the respective Doppler angle can be calculated (law of refraction)
Basics:
(3)
If an ultrasonic wave of frequency fo is hitting a moving object then this causes a frequency shift due to the Doppler effect. For a small velocity of movement of the object v in comparison with the sound velocity c in the medium equation (1) applies: (1)
∆f = f 0
α = 90° − arcsin ( sin α P
cL ) cP
By means of the Doppler angle and the measured Doppler frequency shift Df the mean flow velocity is calculated via (2) (fo=2 MHz).
v ( cos α + cos β ) c
where a and b are the angles between v and the wave normal. For a pulse-echo-system with an ultrasonic sensor a =b is valid and therefore: (2)
∆f = 2 f 0
v cos α c
Results: Values calculated with formula (3): angle of prism 15° 30° 60°
Doppler angle 81,7° 73,8° 61,1°
cos (α) 0,144 0,279 0,483
results and velocity of the movement: 15° pump voltage [V] 3,00 5,00 7,00
30°
60°
∆f [Hz] v [cm/s] ∆f [Hz] v [cm/s] ∆f [Hz] v [cm/s] 185 285 405
48 74 105
342 515 700
46 69 93
570 920 1320
44 71 102
The upper diagram shows that the Doppler frequency shift increases with increasing voltage (velocity) and decreasing Doppler angle. The lower diagram shows that for one velocity the ratio of DF/cos(a) is constant therefore no angle dependent error measurement occurs.
48 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
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Flow profiles Purpose:
Setup:
By means of an ultrasonic Doppler device the difference in the velocity distribution and the concentration distribution of a test liquid shall be demonstrated for laminar and turbulent flows.
Ultrasonic pulse Doppler „FlowDop“ Ultrasonic probe 2 MHz Doppler prism 3/8“ Flexible tubes set Centrifugal pump „MultiFlow“ Doppler dummy fluid Ultrasonic gel
order order order order order order order
PHY14
no no no no no no no
50100 10132 50112 50120 50130 50140 70200
turbulences a quadruplicating of the pressure loss over the same tube section. In a laminar flow a parabolic flow profile results where the maximal velocity in the middle of the tube is twice as large as the mean velocity. In turbulent flow the flow profile flattens distinctly and the mean velocity of flow shifts closer to the maximal flow velocity.
Procedure:
Basics: In a liquid involving friction the flow is laminar for small velocities. That means the coaxial layers of the liquid are pushing side by side without mixing. All liquid particles describe linear pathways parallel to the axis of the tube whereas the velocity increases continuously from the wall of the tube to the inside. At exceeding of a certain velocity suddenly a turbulent movement occurs and the liquid particles do not move on axis-parallel paths anymore. This critical velocity vk results after Reynolds from:
(1)
vK = R e
η ρd
where are r the density, h the dynamical viscosity of the liquid and d the tube diameter. The Reynolds number Re is a dimensionless constant of a value of 2320. For laminar flows the mean velocity of the flow is strictly proportional to the pressure. For turbulent movement the resistance is essentially proportional to the square of the increasing velocity. That means a doubling of the velocity causes at
Using the software the measuring window (gate) can be varied at the FlowDop in the depth. In this way it is possible to get signals only from a limited tube section. The measurement is carried out using a 3/8“ tube with a 15° angle of the Doppler prism (best resolution) for a slow and the maximal flow velocity (adjustment of voltages at the centrifugal pump). The gate is moved in steps of 0.75 mm starting at 30 mm measuring depth for about 15 mm and each time the flow velocity and the intensity value of scattering is measured and plotted in dependence on the measuring depth.
Results: Fig. 1 shows the intensity distribution normalised to the related maximum (corresponds to the concentration in the measuring volume). In the laminar flow an enhanced concentration results in the middle of the tube due to the central migration along the velocity gradient. Because of the updraft (scatterer are lighter than water) an additional enhanced concentration occurs in the upper (transducer-near) region of the tube. The distribution is distinctly expanded in the turbulent flow since a significant gradient does not exist any more. Fig 2 shows flow profiles normalised to the corresponding maxima. For a slow flow rate the typical parabolic course of velocity can be seen that flattens clearly at the transition to turbulence.
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Ultrasonic experiments
PHY15
Mechanics of Flow
Purpose:
Setup:
The fundamental characteristics of stationary laminar flowing liquids are investigated in a tube circulation. The relationship between flow velocity and tube cross section (continuity condition) as well as between flow resistance and tube diameter (law of Hagen-Poiseuille) are examined.
Ultrasonic pulse Doppler „FlowDop“ Ultrasonic probe 2 MHz Set prisms and pipes Centrifugal pump „MultiFlow“ Doppler dummy fluid Standpipe for pressure Ultrasonic gel (2) .
order order order order order order order
no no no no no no no
50100 10132 50201 50130 50140 50150 70200
1 ρ v 2 = p0 2
p+
Only in a friction-less liquid p0 is constant. In a flow pertaining to friction the total pressure decreases in dependence on the viscosity h, the length l, the cross-section A of the passing through region and the flow rate V. For liquids with not too high flow velocities (laminar flow) in narrow tubes the HagenPoiseuille law is valid for the pressure drop Dp: •
(3) ∆p = R V
(4)
R=
8 l η p r4
where R is the radius of the tube and l is the length. That means that a reduction of the diameter of the vessel to half results in an enhancement of the flow resistance to 16 times. By this principle blood vessels regulate the blood distribution between extremities and inner organs.
Procedure:
Basics:
A circulation is built consisting of 3 tube lines of equal lengths but different diameters (1/2“, 3/8“, 1/4“). At the beginning and end of each line is a measuring point of equal diameter (3/8“). At the tube lines the mean velocity is measured for 3 different flow rates (3 different voltages at the centrifugal pump) by means of the Doppler prism and the FlowDop. Knowing the measured flow velocities the flow rate can be determined after (1) and compared. At the measuring points the pressure drop due to the flow resistance can be measured. Calculating the flow rate from (1) the flow resistance can be determined after (4) and from this using the known geometry the dynamical viscosity of the liquid is obtained.
A stationary flowing liquid is characterised by a constant flow of liquid at each point of the system. Therefore the continuity equation for two different tube areas A1 and A2 results as: •
A1 v1 = A2 v 2 = V = const.
(1)
v1 and v1 being the mean velocities in the respective section and V the flow rate (volume per time unit). The static pressure in a flowing liquid is always smaller than in a motionless liquid, and reduces the greater the flow velocity is (Bernoulli equation). For the flow through a horizontal tube (without gravity pressure) the total pressure pO is:
Results:
A (1/2”)=1,1 cm²; A (3/8”)=0,66 cm²; A (1/4”)=0,32 cm² 1/2”
3/8”
1/4”
U [V]
v [cm/s]
v*A [l/min]
v [cm/s]
v*A [l/min]
v [cm/s]
v*A [l/min]
2
16,0
1,06
27,1
1,08
55,6
1,07
3
26,4
1,74
45,3
1,79
92,2
1,77
4
35,7
2,36
57,4
2,27
118,5
2,28
The diagram shows that the flow rate calculated from the measured velocity and the area is nearly the same at all tube diameters for equal voltages and therefore the continuity equation is fulfilled. 1/2”
3/8”
1/4”
U
∆p
R
∆p
R
∆p
R
[V]
[mm H2O]
[g/(s cm4)]
[mm H2O]
[g/(s cm4)]
[mm H2O]
[g/(s cm4)]
2
0,3
16,8
0,8
44,9
3,4
218,3
3
0,5
16,9
1,5
50,8
8,5
902,7
4
0,9
23,5
3,1
80,9
18,0
2484,0
Length of the tube sections: 30 cm d
R
η
[cm]
[g/(s cm4)]
[g/(s cm)]
1,18
16,8
0,027
0,92
44,9
0,026
0,64
218,3
0,030
The mean dynamical viscosity amounts to 0.027 g/(s cm) and this is in the range of the viscosity of water (0.01 g/(s cm)).
50 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Mechanical scan methods Purpose:
Setup:
By means of a computer controlled scanner the B-image of a sample is recorded for 2 different frequencies (1 MHz and 2 MHz) and different local resolutions and the consequences on the resolution power are compared.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Ultrasonic probe 2 MHz Ultrasonic test block transparent or black Computerised Tomography scanner CT control unit Water tank Ultrasonic gel
order order order order order order order order order
PHY16
no no no no no no no no no
10121 10131 10132 10201 10204 60100 60110 60120 70200
Procedure: The sample is put into the water-bath and the respective probe is adjusted in a way that it is moved only a very short distance over the sample surface. With that one avoids the multiple reflections of the surface superimposed with reflections of the sample holes. The scan parameters (sampling rate and total length) are given into the software and the scan for 1 MHz and 2 MHz is carried out at different line densities (250 µm, 1 mm). The images are compared mutually for the same contrast adjustments and judgments about resolution power and focus zone are made.
Basics: To generate a B (Brightness) -image (scan image in sound direction) it is necessary to move the sound head or sound beam, respectively. For this a number of mechanical and electronic sampling methods have been developed. The advantage of automatic mechanical systems is the high image quality due to a good resolution power and a free selectable line density. The disadvantage is a low frequency of image succession and the necessary coupling. For real-time images and moving structures electronic multi-element scanners are therefore used. For the sampling geometries, line scan and divergent resp. convergent sector-scan can be distinguished.
Results: Fig. 1 shows a B-image of the acrylic block (holes are filled with water) recorded with a 1 MHz probe at a sampling rate of 250 µm. Acoustic shadows are distinctly visible in the bottom echo, as well as the reflexes at the beginning and end of the respective holes. The near-field lies in the region up to 2.5 cm and is not very pronounced. Fig. 2 shows a B-image recorded by a 2 MHz probe with the same sampling rate of 250 µm. Since the sound pulse for 2 MHz is distinctly shorter, the axial resolution is improved and the images of the edges of the holes are much sharper. The clearly larger near-field range results in the effect that the surface-near holes are displayed too large. The group of test holes for resolution in the upper left is resolved approx only by the 2 MHz probe. Fig. 3 is a B-image taken by a 1 MHz probe at a sampling rate of 1 mm. There is no significant difference to the measurement with 250 µm, that can not be expected either for a probe of a diameter of 16 mm and a sound field width in the focus of about 5 mm.
Figure 1
Figure 2
Figure 3
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Ultrasonic experiments
PHY17
Sound velocity in water, acoustic lattice
Purpose:
Setup:
Characterisation of the interference maxima developing at the diffraction on a standing acoustic wave regarding amplitude and phase shift. Determination of the sound velocity in a test liquid by frequency variation.
Ultrasonic wave generator SC500 Complete set Debye-Sears Semipermeable reflector 2x adjustable reflector 2x photodiode oscilloscope
For waves is:
l=
c f
order order order order order
no no no no no
20100 20200 20301 20302 20303
,
therefore m can be calculated from:
m=
and for the sound velocity follows now:
∆m ⋅ f m ∆f c=
2 ⋅ h ⋅ ∆f ∆m
.
The sound velocity can be determined by variation of the ultrasonic frequency and the determination of the modulation maxima (standing wave).
Procedure: Basics: The interference maxima developed at the diffraction on a standing ultrasonic wave are amplitude modulated. Thus is caused by the periodic change of the standing ultrasonic wave. The 0-th order has its maximum at the minimum of the standing wave (no diffraction), the n-th orders at the maximum of the standing wave. Minima and maxima appear two times per period at a standing wave. This effect of the light intensity modulation by an acoustic wave is used for acoustooptical modulators (AOM). The modulation amplitude is the largest for the best approximation of the geometry on a standing wave. In this case is:
h = m⋅
l 2
(h...distance between sender and bottom of the reservoir; m... number of half wave lengths n h). Because of the change in frequency the number of half wavelengths will be reduced by (Delta)m. It follows:
h = (m + ∆m) ⋅
l m + ∆m 2
(for the particular modulation maximum)
1. The laser, the adjustable and the semipermeable reflectors and the probe shall be adjusted in a way, that an optimal diffraction image will develop. The intensity of the higher orders and the distances between the diffraction maxima should be as large as possible. (wenn Platz Skizze einfügen). Ultrasonic frequencies around 5 MHz are very suitable for this. With a photodiode the 0-th order will be detected on the oscilloscope and with the second photodiode a higher order (1-st, 2-nd ...). The modulation shall be measured compared to the total amplitude. The phase shift between the orders shall be measured. The frequency of the modulation shall be measured. 2. Only one photodiode without a semipermeable reflector will be used. It shall be adjusted in a way that the 0-th order hits the photodiode. It requires a long light way since the best results will be achieved with sound frequencies between 3 and 5 MHz, but the diffraction maxima are very close together at these frequencies. The complete setup (also the ultrasonic probe) shall be readjusted until the amplitude modulation is maximal. The the generator`s frequency shall be attuned in 100 Hz steps until the amplitude modulation reaches a maximum again. The frequency change shall be registered and the procedure repeated ca. 5 times. With the measured distances between the bottom side of the ultrasonic probe and the bottom of the reservoir and the frequency changes the sound velocity of the test liquid can be calculated.
Results: 1. Modulation amplitude at 0-th ordner: 1-st order: 2-nd order: Phase shift 0-th to 1-st order: Phase shift 0-th to 2-nd order: Phase shift 1-st to 2-nd order: Modulation frequency: 2. h fm
= =
72 mm 4,7300 MHz
f= 4,73 MHz 600-800 mV 200-300 mV 50-100 mV 180° 180° 0° 9,46 MHz
∆m
f [MHz]
∆f [kHz]
c [m/s]
1
4,7403
10,3
1483
2
4,7507
20,7
1490
3
4,7610
31,0
1488
4
4,7714
41,4
1490
5
4,7818
51,8
1492
mean
1489
test liquid: water (20°C) , theoretical value: 1482 m/s
52 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Phase shift on the acoustic lattice Purpose:
Setup:
Characterisation of the interference maxima which develop at the diffraction on a travelling acoustic wave regarding their frequency shift.
Ultrasonic wave generator SC500 Complete set Debye-Sears Semipermeable reflector 2x adjustable reflector Photodiode Ultrasonic absorber oscilloscope Doppler effect:
order order order order order order
PHY18
no no no no no no
20100 20200 20301 20302 20303 20227
c sin (ϕ n ) n n = n 1 + c L
with cL being the sound of light. With c = l f, cL = L n and the conditions of the n-th interference order
L ⋅ sin (ϕ n ) = n ⋅ l follows: (1)
n n =n + n f
Procedure: Basics:
Unlike a standing acoustic wave the light diffraction on a travelling acoustic wave is time-constant. The amplitude of the density modulation does not change, the wave just propagates. It is a time-constant, local variable lattice. A standing wave shows a time variable, local-constant lattice. The intensity of the light beam is time-constant in all orders. The beam will only be deflected but not amplitude modulated. This effect finds its application as acousto-optical deflector (AOD). However, the movement of the acoustic lattice causes/generates a frequency shift of the laser light. At a travelling sound wave with the velocity c a frequency shift in the diffracted beams is generated for the frequency of light n due to the
An ultrasonic absorber in the reservoir impedes the development of a standing wave. The frequency shift of the laser light is very small since the ultrasonic frequencies are in the area of 5-10 MHz. To measure this frequency shift two beams of different orders and different frequencies have to be mixed on the photodiode. On the signal an interference with the frequency difference of both orders will be developed. Therefore both beams have to hit the photodiode parallel which can be realised with a good adjustment of the reflectors. To receive a larger interference amplitude signal it is recommended to reflect the weaker beam (e.g. -1-st order) directly with the semipermeable reflector and the stronger beam (e.g. 0-th order) with a circuitous over the adjustable reflectors to the photodiode. If possible the interference between the -1-st and 1-st and 2-nd orders shall be measured. After equation (1) the interference frequency in these cases is 2f and 3f.
Results:
The following images demonstrate the superposition of the diffracted beams of different orders. The sound frequency is ca. 9 MHz. It can be seen that the interference frequency increases linear with the distance of the order number from f @ 9 MHz (a) to 3f @ 27 MHz (c).
a. Superposition of the -1-st and 0-th orders
c. Superposition of the -1-st and 2-nd orders
b. Superposition of the -1-st and 1-st orders
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Ultrasonic experiments
PHY19
Phase and group velocity
Purpose:
Setup:
The ultrasonic phase velocity shall be determined in a test liquid for various frequencies. Additionally, the group velocity of a short ultrasound impulse will be measured. The dispersion of the sound velocity in the test liquid depends on phase and group velocity.
Ultrasonic wave generator SC500 Hydrophone set Multifrequency probe Ultrasonic gel oscilloscope
order order order order
no no no no
20100 10251 20138 70200
Since the frequencies are known, the phase velocity can be calcP = f * l culated without any other measurements: The group velocity can be calculated from the time of flight t and the distance probe- hydrophone s: cG = s / t
Procedure: The multifrequency probe will be connected to the water filled reservoir using ultrasonic gel and the hydrophone with holder will be placed in the reservoir. The hydrophone signal will be connected to an oscilloscope (channel 1). The sinus signal output of the ultrasonic generator will be connected to channel 2 of the osci. For measurements in the frequency area of 5-10 MHz the time base on the osci is 100 ns/div or 50 ns/div. The amplitude of hydrophone and sinus output shall be calibrated to one another. The distance between probe and hydrophone will be measured. Afterwards, slow and steady the hydrophone will be moved away from the probe and the number of detected zero crossings of the curves can be measured. The distance between shall be again measured after a certain amount of phases to determine the difference to the starting point. This should be repeated for 5 distances. Wave length and phase velocity then can be determined. The whole process should be performed for various frequencies in the area between 5 and 10 MHz to receive information if the phase velocity depends on the frequency. The time of flight of an ultrasonic impulse can be measured (TTL exit as trigger) by switching to pulse mode on the ultrasonic generator and choosing 1kHz repetition rate. The group velocity will be calculated out of the measured distance between probe and hydrophone and the time of flight.
Basics:
The effect of dispersion demonstrates how the phase velocity depends on the wave length. The group velocity cG follows by phase velocity cP after: dc cG = cP − l P dl If the distance (Dl) between probe and hydrophone changes, the phases of the signal move on. ∆l ⋅ 2p ∆φ = l The signals overlap repeatedly when moving forward. ∆φ = 2π ⋅ n , n=1,2,... The wave length can be determined from the distance between probe and hydrophone. ∆l ⋅ 2π ∆l l= = ∆φ n
Results:
Dispersion in water
The phase velocities for 6 frequencies and 5 distances were determined, mean values and standard deviations calculated. The distances were measured with a calliper.
f in MHz n
0
20
40
60
80
100
λ
c
5
x
40,3
46,3
52,2
58,1
64
70
λ
0.3
0.298
0,297
0,296
0,297
297,5+/-1,5
1487,4+/-7,4
c
1500
1487,5
1483,3
1481,3
1485
6
x
50,5
55,4
60,5
65,4
70,4
75,4
λ
0,245
0,25
0,248
0,249
0,249
248,2+/-1,9
1489,3+/-11,4
c
1470
1500
1490
1492,5
1494
7
x
43,9
48,2
52,4
56,6
60,7
64,9
λ
0,215
0,213
0,212
0,21
0,21
211,8+/-2,1
1482,8+/-14,5
c
1505
1487,5
1481,7
1470
1470
8
x
36,7
40,4
44,1
47,9
51,5
55,3
λ
0,185
0,185
0,187
0,185
0,186
185,5+/-0,8
1484,3+/-6,1
c
1480
1480
1493,3
1480
1488
9
x
38,2
41,5
44,8
48,2
51,4
54,9
λ
0,165
0,165
0,167
0,165
0,167
165,7+/-1,0
1491,6+/-9,1
c
1485
1485
1500
1485
1503
10
x
42,8
45,8
48,8
51,7
54,6
57,5
λ
0,15
0,15
0,148
0,148
0,147
148,6+/-1,4
1485,7+/-13,9
c
1500
1500
1483,3
1475
1470
sound velocity in m/s
x....distance probe hydrophone n...number of peaks c...velocity
1500 1490 1480 1470 1460 1450 120
170
220
270
320
wave length in 10^-6 m Pulse measurement: l = 10 cm t = 67,3 µs Group velocity v = 1485 m/s. The diagram shows that there is no change in the phase velocity depending on the frequency (dcP/dl). This demonstrates that the phase velocity does not depend on the wave length. No dispersion in water appears in this frequency range. An additional comparison with the group velocity confirms this conclusion.
54 Ultrasonic experiments
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www.gampt.de
Determination of the focus zone Purpose:
Setup:
The sound field intensities of three ultrasonic probes of different frequencies shall be measured along the acoustic axis. The near field lengths (focus zone) of the probes shall be calculated from the measuring curves and compared with the calculated values.
Ultrasonic echoscope GAMPT-Scan Hydrophone set Ultrasonic probe 1 MHz Ultrasonic probe 2 MHz Ultrasonic probe 4 MHz Ultrasonic gel
order order order order order order
PHY20
no no no no no no
10121 10251 10131 10132 10134 70200
Procedure: The exact adjustment of the hydrophone to the sound axis is very important for the measurement along the acoustic axis of a probe. The particular ultrasonic probe shall be connected to the reservoir with a good amount of gel. In reflection mode the signal amplitude shall first be adjusted to a maximum (side adjustment of the probe, height and turning of the hydrophone) while the distance between hydrophone and probe shall be maximised. Now switch to transmission mode and choose the appropriate amplification properties. The amplitude response will be measured along the sound axis by moving the hydrophone holder. It is recommended to measure the position of the hydrophone using the depth scale in the software.
Basics: Ultrasonic probes show a different axial and lateral resolution depending on their frequency. Additionally, the area with the highest resolution can be found in different distances in front of the probe area. The reason for this is because of the different sound field geometries of the probes. Because of interferences a sound field builds up on a round ultrasonic probe which can be classified in two areas. The near field is characterised by strong amplitude modulations. The far field shows a sound beam with decreasing amplitude. The distance of the last amplitude maximum before the monotonically decrease is called near field length (S). It can be calculated for a simple ceramic disk with the radius (r) and the wave length l after the following equation: S = r²/l The sound beam shows here a contraction called focus zone. In this area the biggest lateral resolution of an ultrasonic probe can be expected.
Sound field of a 2 MHz probe with a diameter of 16 mm
Results:
1 MHz, S = 42,6 mm (sound velocity of water: 1500 m/s) 2 MHz, S = 85,3 mm 4 MHz, S = 170,6 mm The measured maxima for the 1 MHz and die 2 MHz probe are located in the calculated near field length. The signal amplitude varies strongly in the whole measurement range for the 4 MHz probe since the measuring area is inside the near field. The probes are a pulsating probes with a very wide spectrum, this explains the strong variations.
1,1
1 amplitude (normalize)
The measured amplitudes for each probe shall be presented in standardised form in a diagram. For each frequency the near field length in water shall be calculated at a probe radius of 8 mm (the active probe area is smaller then the geometrical radius) and charted as vertical lines in the diagram.
0,9 2MHz 0,8
1MHz 4MHz
0,7
0,6
0,5 20
40
60
80
100
120
140
160
180
distance in mm
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Ultrasonic experiments
IND01
Non Destructive Testing (NDT)
Purpose:
Setup:
For a normal probe an adjustment of the ultrasonic device shall be carried out for the location of a discontinuity. The determination of the size of the discontinuity is done by shifting the test head and by using the DGS diagram (distance-gainsize). The DGS diagram shall be examined. By means of timedependent amplification a horizontal evaluation line shall be adjusted in the DGS diagram.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Ultrasonic test block or black Ultrasonic gel
order order order order order
no no no no no
10121 10132 10201 10204 70200
The DGS diagram shows the functional relationship between the depth (D), the relative echo amplitudes (Gain), and the discontinuity size (S). The distance D is represented relative to the near-field length xN: A = x/xN,
xN =0,25* d²/λ
The discontinuity size is given relative to the diameter of the probe ceramic d: G = DU/d The amplitude HU is related to the amplitude of an infinite extended reflector HO with a distance zero: V = 20 log HU/H0
Basics:
Procedure:
In the NDT different test heads are employed for different test tasks. For the pulse-echo-method normal probes are used for longitudinal waves of perpendicular incidence. The discontinuity is located by reflection of the sound wave. The time of flight is a measure for the depth of the discontinuity and is dependent on the respective velocity of the material. Since the echo amplitude depends not only on form and size of the discontinuity, but also on the damping of the material and the characteristic of the sound field, an exact determination of the size is often problematic. The size of the located discontinuity is determined by sampling for large spacial extensions. For that the test head is moved over the whole discontinuity and each time the distance from the full echo to the drop of half of the signal is determined. For smaller discontinuities the measured echo amplitudes are compared with signals of an idealised substituted discontinuity. The amplitude values of the substituted discontinuity are plotted as DGS diagrams.
For the sample the sound velocity of the material is determined using a suitable back wall echo and the display of the GAMPT-scan is adjusted in a way that the depth is directly readable. The amplitudes of the bottom echoes of the test block are determined for two different layer thicknesses and from that the amplitude for the layer thickness zero is calculated via the attenuation law. For the diagonal group of drillings the depth and the amplitude are determined, respectively. For that, the time-dependent amplification (TGC) is adjusted to zero. All holes are measured from all four sides as far as possible. From the measured results the data for the DGS diagram are calculated. By means of the TGC the signals for the row of holes of equal size are adjusted to a constant amplitude. For all holes of the group again the amplitudes are determined from one surface of incidence and the calculated data are entered into the DGS diagram.
Results: Determination of sound velocity: 0,00
-10,00
-20,00 V = 20 log HU/H0
Measured value: t = 60 µs; s = 80,7 mm; c = 2*s/t = 2690 m/s Calculation of near-field length: f = 2 MHz; d = 16 mm; λ = c/f = 1,345 mm; xN = 0,25*d²/λ = 47,5 mm Calculation of the comparative amplitude HO: Attenuation law: H2 = H1 e-µx From this follows for the amplitudes of two different layer thicknesses: µ = 1/(x1-x2) ln (H2/H1); Measured values: x1 = 2*40,6mm = 81,2 mm (twice length for the echo); H1 = 1,029 V x2 = 2* 80,4 mm=160,8 mm; H2 = 0,106 V µ = 0,0286 [1/mm] With that the amplitude for an infinite extended reflector at the distance zero can be calculated: H0 = H1*eµx1 = 10,496 V
-30,00
D=3mm D=4mm
-40,00
D=5mm D=6mm D=3mm mit TGC
-50,00
Bodenechos -60,00 0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1,60
1,80
2,00
A = x/xN
56 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
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Rayleigh waves Purpose:
Setup:
The generation and expansion of Rayleigh waves are investigated in an aluminum specimen. At first the sound velocity of the Rayleigh wave is determined. At cracks of different depth in the specimen the dependence of the transmission amplitude on the crack depth is examined.
Ultrasonic echoscope GAMPT-Scan 2x ultrasonic probe 1 MHz 2x Rayleigh waves attachments Material sample for Rayleigh Waves investigations Ultrasonic gel
IND02
order no 10121 order no 10131 order no 10231 order no 10232 order no 70200
Procedure: For the determination of the velocity of Rayleigh waves an ultrasonic probe with a Rayleigh wave attachment as transmitter is adjusted at one end of the specimen and the receiver with attachment is installed at distances from 5 cm to 50 cm in steps of 5 cm. The distance is measured between edges of probes facing each other. Now the time of flight between the transmitter pulse (ca 0.1 µs) and beginning (or maximum) of the echo is determined. The sound velocity follows from the ratios of the differences of distance and the time of flight per pair of measurements. Thereby the influence of the point of length measurement and of the attachment is eliminated. At cracks of different depths the transmitter and receiver are positioned on both sides at always the same distance from the crack and the transmission amplitude is measured. This is put into proportion to the amplitude without a crack and the coefficient in dB in relation to crack depth is plotted (or the relative crack depth versus Rayleigh wavelength is plotted).
Basics: Rayleigh waves are a member of the group of interface waves, the expansion of which occur along the interfaces of differences of acoustic impedance. The Rayleigh wave (also surface wave) exists at the free interface of a solid and represents a combination of longitudinal and transverse displacements of particles. Rayleigh waves are used in the nondestructive material testing for the verification of surface defects. The generation takes place by means of a 90° test head by mode conversion of longitudinal waves into Rayleigh waves by putting on a perpendicular thickness oscillator with comb (GAMPT-10321, Raleigh wave attachment). The edges of this comb are in resonance with the Rayleigh wavelength. Another possibility to produce Raleigh waves is using the interdigital transducer (IDT). The reflected or transmitted amplitude of the Rayleigh waves can be put into relation to the crack depth in the range of small crack depths (crack depth in the range of the wavelength).
Results: From the measured values, after taking the average, follows a sound velocity of the Rayleigh wave of about 2920 m/s in aluminum. With that a wavelength λ of 2.92 mm follows for a frequency of 1 MHz. The transmission measurement with probe distances of each 5 cm from the respective crack yields the following amplitudes (see next table). A nearly linear relation results between the crack depth and the transmission amplitude in dB corresponding to the exponential drop of amplitude of the Rayleigh wave with the penetration depth.
path [mm] 50 100 150 200 250 300 350 400 450 500
time [µs] puls front
23,3 40,5 58,5 75,4 92,3 109,1 125,7 142,1 159,5 175,9 mean SD literature value
vSUR [m/s]
2907 2841 2879 2899 2914 2930 2946 2937 2949 2911 35 2900-2950
time [µs] puls max.
vSUR [m/s]
29,8 47,6 64,4 80,1 97,0 114,6 131,0 147,2 164,5 181,3 mean SD
2809 2890 2982 2976 2948 2964 2981 2970 2970 2943 58
crack depth [mm]
crack depth/ wave length
amplitude [mV]
attenuation [dB]
0,0 0,8 1,2 2,0 2,8
0,00 0,27 0,41 0,68 0,96
676 469 271 164 92
0,0 -3,2 -7,9 -12,3 -17,3
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
IND03
Level measurement
Purpose:
Setup:
For an arbitrary formed vessel a calibration curve shall be taken for an ultrasonic fill level measurement. Then the calibration is checked by means of a defined filling.
Ultrasonic echoscope GAMPT-Scan order no 10121 Ultrasonic probe 2 MHz order no 10132 Ultrasonic gel order no 70200 Water tank, stand, measuring cylinder
probes configurations for level measurements
material independent level measurements limit switch
level switch
level measurement (material dependent)
Basics: Measurements of fill level play an important role at many industrial processes, e.g. at filling-stations, reactors, reservoirs or tanks. Ultrasonic devices for fill level measurements are suitable particularly for the control of the state of liquids. They are applicable for almost every media, for overlaying of several media, in the case of foaming and also for very aggressive liquids, since the measurement takes place through the vessel wall. According to the damping of the liquid and the demanded accuracy ultrasonic - frequencies from 40 kHz to 5 MHz are applied. Basically two types of measuring devices are in use: Threshold switch and fill level measurement. In the graphic some measuring devices with the corresponding measuring signals are shown. To measure the liquid volume in a tank a sensor is attached at the bottom side and the time of flight of the reflection of the liquid surface is determined.
Procedure: By means of a suitable tripod the 2 MHz probe is fixed to an appropriate vessel in such a way, that a perpendicular direction of incidence from below is achieved. The probe is coupled by ultrasonic gel to the vessel wall. After filling the vessel with a defined liquid volume a good detectable echo of the liquid surface is adjusted by means of the transmitter power, the receiver power and the TGC. Thus the time of flight is determined. Then the vessel is filled in several steps and to each filling volume the time of flight is measured. After evaluating the calibration curve any fill levels of the vessel can be determined.
Results: For the very simple formed vessel used here (conical vessel, truncated cone) the calibration curve of the filling measuring device can be fitted by a second-order polynomial. The filling volume of the vessel follows from the time of flight after the equation: V[ml] = 1,94 + 2,23*TL[µs] + 0,0033*TL² TL….. Time of flight For the measured filling height with a time of flight of 122.5 µs a filling volume of 324.6 ml results. By means of a graduated cylinder a volume of 325 ml has been determined. For very irregularly formed vessels that contain additional installations, the filling volume can be read directly from the calibration curve.
58 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Concentration measurement Purpose:
Setup:
The dependence of sound velocity of a salt solution on the concentration is determined by means of the Debye-Sears effect and is compared with an empirical equation for the sound velocity in sea water after Mackenzie.
Ultrasonic wave generator SC500 Complete set Debye-Sears Salt, stirrer, thermometer
(1)
lS =
IND04
order no 20100 order no 20200
2 N lL s x
The empirical formula for the sound velocity in sea water after Mackenzie (JASA, 70,807-12) is: (2)
c = 1448.96+4.591*T-0.05304*T²+0.0002374*T³ +1.34*(S-35)-0.01025*T*(S-35)
With T = temperature [°C], S = concentration of salt [g salt/ kg sea water.
Procedure:
Basics: With increasing concentration in electrolytes a decrease of compressibility follows. This leads to a concentration-dependent increase of the sound velocity. From the diffraction patterns of the Debye-Sears experiment (PHY11) the wavelength of the sound wave can be determined and with that the sound velocity of the liquid can be calculated. The distance between the ultrasonic source and the diffraction patterns has to be measured, the number of diffraction maxima N and the distance between the -Nth and the +Nth diffraction order x must be determined. From the known wavelength of the laser light lL the wavelength of the ultrasonic wave lS can be calculated:
The distance between the ultrasonic transducer and the diffraction pattern s is measured by a tape. The maximal diffraction order N is determined and the distance between the -Nth and the +Nth diffraction order x is measured by a caliper. The measuring is carried out for a frequency with a large distance of diffraction maxima and still sufficient number of maxima e.g. 9 MHz and with the red laser (larger diffraction distance). From the results of measurements after (1) the wavelength of sound ls is determined and with the known frequency f the sound velocity c is calculated by c=f*ls. A respective amount of rock salt is added in order to enhance the concentration stepwise from 0 to 10 mass per cent. After complete solution the measurement is repeated. The temperature of the solution is measured in order to take into account the dependence of the sound velocity on temperature. The measured and after (1) calculated sound velocities are plotted versus the concentration.
Results: distance s=3220 mm
frequency f=9,0 MHz
c c (2) S x λS mess [m/s] [g/kg] [mm] [µm] [m/s] 0 10 20 30 40 50 60 70 80 90 100
51 50,6 50,1 49,5 48,9 48,3 48,2 47,9 47,3 46,9 46,7
164,7 166,0 167,6 169,7 171,7 173,9 174,2 175,3 177,5 179,1 179,8
1482 1494 1509 1527 1546 1565 1568 1578 1598 1612 1618
wave length red laser λL=652 nm
N=2
T [°C]
1485 21 1496 21 1507 21 1519 21 1531 21,5 1542 21,5 1555 22 1566 22 1577 22 1588 22 1599 22
The sound velocity increases clearly with the increasing concentration of the salt solution and shows in the measuring range (0 - 10% (g/g)) an almost linear dependence. The measured values (red curve) agree in the range of small concentrations (< 3%) with the theoretical values.
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GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
Ultrasonic experiments
IND05
Flow measurement
Purpose:
Setup:
The dependence of the measured Doppler frequency on the flow rate shall be determined for a fixed measuring arrangement (tube diameter and Doppler angle). By means of the investigated dependence a flow meter can be calibrated, by which the flow rate can be measured using a pump.
Ultrasonic pulse Doppler „FlowDop“ order no Ultrasonic probe 2 MHz order no Doppler prism 3/8“ order no Flexible tubes set order no Centrifugal pump „MultiFlow“ order no Doppler dummy fluid order no Ultrasonic gel order no Mariotte-bottle, measurement cylinder, timer
50100 10132 50112 50120 50130 50140 70200
the employment at arbitrary flow velocities below the sound velocity. The Mariotte-bottle is closed at the upper end by a plug and is supplied at the lower end with an outlet. Through the upper plug leads a glass tube which is open at both ends. If liquid runs out of the bottle then the air pressure decreases above the water level. This pressure is equalised via the glass tube which projects into the liquid (air bubbles rise up). Therefore only the water column between the outlet and the lower end of the glass tube is responsible for the volume flow. Thereby an equal flow is obtained even for the lowering of the total water level.
Procedure: Basics: The employment of ultrasonic methods to measure flow rates in liquids arises from the necessity of touch-free and recoiling-free measuring principles at low effort. Because of the dependence of Doppler frequency shift on the velocity and due to the proportionality between flow rate and the mean velocity in a constant cross section, the Doppler effect can be used for flow measurements. This is however only possible for liquids having a sufficient number of scattering particles (e.g. blood, liquids with gas bubbles) and for which the scattering angle is unlike 90°. The advantage lies in the very high sensitivity, the possibility of local resolution and
Using a 3/8“ tube as measuring distance a Doppler prism is attached. The maximal Doppler angle (60° prism angle) is used. The tube is connected to a Mariotte-bottle. By changing the height of the glass tube or by changing of the total resistance (by means of a clamp at the outlet) five different flow rates are adjusted. These are measured by a measuring cylinder and a stopwatch. The averaged Doppler frequency shifts, determined for the respective flow rate, are plotted in a diagram. From the slope of the curve follows the calibration factor for our flow meter (tube with prism). Now the tube is connected to the centrifugal pump and the flow rate (Doppler frequency shift with calibration factor) is determined in dependence on the control voltage.
Results:
Measuring result with Mariotte-bottle: V [l/min]
f [Hz]
0,4
120
0,7
215
0,95
293
1,25
380
1,5
460
1,8
543
From the diagram follows a slope of a=265 Hz/(l/min) and for the determination of the flow rate from the Doppler frequency shift a calibration factor of : K= 0.00331 l/(min Hz). Therewith the flow rate can be determined for measurements with the pump (flow meter). Results with pump: U [V]
∆f [Hz]
V [l/min]
2,00
293
0,97
3,00
500
1,66
4,00
680
2,25
5,00
890
2,95
6,00
1070
3,54
7,00
1233
4,08
60 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Angle beam measurement Purpose:
Setup:
An angle beam probe shall be adjusted for the discontinuity location in aluminum. For this the length of the delay line, the sound velocity of the transverse wave and the incidence angle of the test head as well as the beam exit point of the delay line are determined. The adjustment of the test head is controlled at a cylindrical discontinuity with half and full skip distance.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Delay line for angle beam 38° Sample for angle beam test Ultrasonic gel
Basics: While for normal probes the adjustment of the distance follows simply from the time of flight and the sound velocity, in the case of the angle test head the respective incidence angle, the length and the exit point of the delay line have to be determined. For the adjustment different control samples or the distance adjustment by projection intervals can be used. The control sample has an arc-like reflector whose echoes come independently of the incidence angle always from the same depth. By clever positioning of an incision multiple echoes are generated, so that the influence of the delay line length tv is eliminated. The exit point is for maximal amplitude exactly at the circle center. This position is given usually as distance xv from the test head edge. At a cylindrical reflector (drilling) the incidence angle can be read from a scale.
order order order order order
IND06
no no no no no
10121 10132 10234 10240 70200
With this follows the simple path length between the surface and the bottom side, also called skip distance after: xa ²= a² + (p1-p0)² and the angle of incidence: tan β = (p1-p0)/a. The sound velocity can be calculated from the difference of both measurements. With the double path length for the echo and the measured time of flights t0 and t1 the sound velocity follows from: c = (4xa – 2xa)/(t2-t1) = 2xa/(t2-t1) Using the known sound velocity finally the time of flight of the delay line can be determined: tv = t1- 2(xa/c) For the location of discontinuities this value must be subtracted from the determined times of flight of the echoes. The depth T of a discontinuity and the projection distance P resp. the shortened projection distance P´ of a discontinuity are calculated as follows: T = c(t-tv)/2 * cos β P = c(t-tv)/2 * sin β P’ = (c(t-tv)/2 * sin β) - xv
Procedure: The angle delay line is coupled to the ultrasonic probe by coupling gel. The angle test head is moved on the test sample as long as the first echo near the test sample edge has a maximum. By rotating the test head the incidence plane is aligned onto the axis of the test sample. At the maximal echo the time of flight and the distance of the test head to the sample axis are measured. From the measuring data the required data of the test head are calculated. Consequently the echo of the half and full skip distance is measured on the cylindrical discontinuity.
Results:
In case of adjustment by projection distances the maximal angle echoes are measured at the edge of two plane-parallel surfaces with known distance and from this all required values are calculated. Exit point of sound: xv = p1-2*p0
Height of sample: a = 25 mm Mean projection distance: P = 24 mm Exit point of sound: x0 = 20 mm Sound path: xA = 34,6mm Sound velocity: c = 3108 m/s. Angle of incidence: b = 43,8° Time of flight of delay line: tv = 17,2µs Measurement of discontinuity: t = 31,7 µs Sound path xA = c(t-tv)/2 xA = 22,5 mm For the verification of the depth we recommend you determine the centre of the drilling, since the point of incidence of the sound wave onto the drilling is difficult to measure. With that the sound path xA becomes longer by the radius (4 mm) of the drilling. For the depth and the projection distance one gets: T = (xA+4) * cosβ T = 19,12 mm P = (xA+4) * cosβ P = 18,34 mm
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Ultrasonic experiments
IND07
Time of flight diffraction technique (TOFD)
Purpose:
Setup:
At a sample two methods of determination of crack-depth are carried out. Cracks of materials with different depths are investigated by means of the ultrasonic angle test head and the results of measurements compared in view of capability and detection limit.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Delay line for angle beam 38° Test block with cracks Ultrasonic gel
order order order order order
no no no no no
10121 10132 10234 10241 70200
ment of the probe applies x = x2-x1= s2-s1 and for the thickness D= T0+T. By simple geometric considerations follows: T = D−
2
2
1
1
a −x
= D−
a
2
1
−
(x 2 − x) 2
with
x
2
=
2
a −D 2
2
.
The sound paths a1 and a2 come up from the half time of flight and the sound velocity: a1=t1*c/2 und a2=t2*c/2.
Basics: For the judgment of mechanical crack behavior of components material defects such as plane cracks are dealt with. For the judgment test specifications are defined which are not allowed to be exceeded. For this accurate indications are needed concerning the geometry of defects such as crack depth, crack length and position of deep cracks. Surface cracks can be detected very sensitively by ultrasonic angle beam transducer. For that the corner effect is used, i.e. an echo generated between the crack and the surface. This echo is greater the deeper the crack extends in the material. However this applies only for cracks smaller than half the probe diameter. The deeper cracks cannot be distinguished. A precise analysis of deeper cracks can be achieved by the TOFD method (time of flight diffraction). For that the diffraction of sound waves at the crack tip is utilized. The sound wave originating at the crack tip produces (besides the corner effect echo) a timeshifted diffraction echo. From the position of both echoes the depth of the crack can be determined. Starting from an angle beam transducer with known material thickness, a known sound velocity of the material c and of the delay line VO [µs] the crack depth follows from the equations: With the measured probe distances s1 (distance between probe front edge and edge of work piece) in the maximum of the corner echo and s2 in the maximum of the diffraction echo and the corresponding times of flight t1 an t2 for the displace-
Procedure: By means of the angle beam transducer (delay line length 16.7 µs; angle of incidence 43, transverse sound velocity of aluminum 3040 m/s) the corner echo of each crack is measured. For that the test head is moved and rotated so that the echo reaches a maximum. The time of flight and the amplitude are measured and the distance from the front edge of the probe to the edge of the work piece is determined. Then the diffraction echo at the crack tip is looked for and is likewise adjusted to maximal amplitude. The time of flight and the probe distance are measured in the maximum. The corner echoes are plotted versus the crack depth. For the diffraction echoes the crack depths are calculated corresponding to the given formula and are represented in a diagram too.
Results: The determination of the crack depth by the corner echo amplitude is, for small depths, the best method to obtain the highest sensitivity. By determining the echo amplitude at comparative samples (nut characteristic line) the crack depth can be estimated. For crack depth in the range of the half of probe diameter (probe diameter 16 mm) the echo amplitude goes into saturation, then an estimation of the crack depth is impossible. However the cracks can be located and the crack length can be examined. By means of the TOFD method the smallest crack (crack depth 2 mm) could not be detected because the diffraction signal was covered by the corner echo. With increasing crack depth the diffraction signal can be measured separately from the corner echo. From the distance between the corner echo and the diffraction echo the crack depth results. The TOFD method can be utilised also for very large crack depths. A complete examination of the material arises however best by the combination of both test methods.
62 Ultrasonic experiments
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www.gampt.de
Detection of discontinuities Purpose:
Setup:
At a sample with various types of discontinuities different location techniques shall be carried out, first by scanning of the sample, then for each discontinuity the signal-noise-distance is examined for an angle beam probe and a normal probe, respectively. The results are discussed concerning the choice of the right location technique for a special test task.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Delay line for angle beam 38째 Test block with discontinuities Ultrasonic gel
order order order order order
IND08
no no no no no
10121 10132 10234 10242 70200
Procedure:
For the investigation of the signal to noise level of the test reflectors in the test sample, using at first the 2 MHz normal probe and then the 45째 angle beam probe, the power of transmitter and receiver is adjusted in such a way, that none of the reflector signals is over-driven. Afterwards the sample is scanned manually. For that appropriat parameter can be chosen in the program. The scan images give an overview of the position and the signal amplitude of the defects. The signals produced by scattering (weak interaction) at the edges of the reflectors are judged as noise.
Basics:
The non-destructive testing by ultrasound requires information about the geometry of the sample and the position and alignment of the discontinuities, in order to radiate the sound into various directions and to receive the sound from different directions, respectively. The direction of incidence is measured always relative to the normal of the surface. From the direction of the incident wave three classes of location methods are distinguished: normal (perpendicular), oblique and orthogonal direction of incidence. The received signal amplitude is dependent on the type, the size and the alignment of the defect. Two principal interactions of the defect and the ultrasound are distinguished: the reflection (strong interaction) and the scattering (weak interaction). The reliable detection of the discontinuity in the test sample requires a sufficient signal to noise distance level of the chosen location A = 20 log US/UR [dB] technique: where UR is the noise amplitude and US is the signal amplitude. For the detection limits of the individual defects and the location methods registration thresholds are defined. Since the ultrasonic echoes of real defects are built mostly of a mixing of reflection and scattering the interpretations can become easily wrong for low thresholds of registration. For the detection of defects with strong interactions the sensitivity of the ultrasonic device must be adjusted by using appropriate idealised test reflectors. As test reflectors mainly circular discs (bag holes), cylinders (through drillings), back walls and angle mirrors are used in different geometrical alignment.
Results:
In the scanning image taken with the normal probe all discontinuities are very clearly visible by the vanishing back wall echoes. But only the echoes of the back wall, of the circular disc and of the horizontal cylinder have sufficiently strong signal amplitude. The remaining echoes are generated at edges by scattering effects. In the case of the angle beam probe the strongest echoes appear for the crack, the oblique crack and also for the horizontal circular disc. As noise threshold the maximal amplitude of the scattering echoes is assumed. In the diagram of the signal to noise distances for the individual test reflectors one observes, that for the location of the back wall and the horizontal cylinder only the normal test head is applicable, on the other hand for the perpendicular and the oblique crack only the angle beam probe is usable. The horizontal circular disc could be localised by both techniques.
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Ultrasonic experiments
MED01
Ultrasonic TM-mode
Purpose:
Setup:
Using a simple heart model the wall motion is recorded by means of the ultrasonic time-motion method (M-mode). From the M-mode recording the heart frequency and the heart volume (HZV) are determined.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 4 MHz Heart model
Heart Diastole
order no 10121 order no 10134 order no 10220
Heart Systole
motion of the cardiac wall and the valves are recorded. From the changes of the cardiac wall distances and of the cavity area in the B-image the cardiac output can be calculated. From the measurement of the end-diastolic and the end-systolic ventricular diameter (distance of the cardiac walls) the corresponding heart volumes EDV (end-diastolic volume) and ESV (end-systolic volume) are determined. From this the heart time volume comes out via:
Basics: In echo-cardiography a special ultrasonic method is applied for the investigation of the heart movements. The time-motion-mode, called also TM- or short M-mode, is indicated particularly as one dimensional technique but shows still two dimensions: one spatial dimension (superimposed interfaces or structures) and one temporal dimension (changes of the structures in the systole and diastole). By means of the TMmode the motion of heart structures (cardiac wall, septum or cardiac valve and vessel valve) are displayed as picture points of different brightness. This form of recording yields an anatomically unusual image. For the determination of cardiac extensions, e.g. of cardiac walls and cardiac cavity diameter, the TM-mode is the investigation technique of choice. Also the judgment of the opening of heart and vessel valves is a domain of the TM-mode. For image recording first an appropriate region of the heart is chosen in the B-image (e.g. the long heart axis), then the M-mode is activated and the
HZV = (EDS-EDV) * HF
HF = heart frequency.
Procedure: After filling the heart model with water the probe shall be fixed to a tripod in such a way that the echo of the membrane appears at a sufficient distance to the impingement surface. Since in water the attenuation of the ultrasonic wave is negligible the measurements can be performed without use of the TGC. The software parameter „sound velocity” is adjusted to water (1480 m/s). After that one switches the software to the M-mode. By periodically compressing the rubber ball the rubber membrane simulates the heart wall motion. The periodical motion of the membrane is recorded in the M-mode and can be printed.
Results:
From the recorded M-mode image first the mean heart frequency is determined over some heart cycles. For this the time distances of the neighbouring heart cycles are measured and the average is calculated: Pulse duration: DT = 0,8 s Heart frequency: HF = 1/DT = 1,25 Hz For all heart cycles the end-systolic diameter ESD (distance of the maximum of the curve from state of inactivity) of the heart model is determined. Mean = 14,6 µs By using the sound velocity we get for ESD = c * t = 1480 m/s * 14,6µs ESD = 21,6 mm The heart volume is obtained under the assumption of a cone as model volume ( V = 1/12 * p * D² * h) with a diameter of 45 mm. From that follows: ESV = 1/12 * p * D² * ESD ESV = 11,45 cm³ = 11,45 ml The end-diastolic volume is taken as zero in this model case. Therefore the heart time volume can be calculated: HZV = ESV * HF = 14,3 ml/s
Distance of the pulse maxima [sec]: 0,8 0,8 0,9 0,8 0,7
Mean= 0,8 sec
Difference pulse minima and maxima [µs]: 15,7 14,9 14,3 14,6 15,0 13,4
Mean = 14,6 µs
64 Ultrasonic experiments
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Ultrasonic investigation with the breast dummy Purpose:
Setup:
In this experiment a typical application of ultrasound in medical diagnostics is given. At a realistic breast model a non-malignant tumor is diagnosed and by means of the brightness scan imaging method it can be localised and measured.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 1 MHz Breast dummy with tumor Ultrasonic gel
order order order order
MED02
no no no no
10121 10131 10221 70200
tissue (or the changed tissue density) distort the image of the mammogram. The mamma sonography so complements the mammography. For young patients the mamma sonography can be sufficient without mammography. An experienced physician using an advanced device detects knots in the breast up about 0.1 cm in size. Recent investigations show that the detection rate in comparison to mammography is nearly the same. In big and dense breasts ultrasound is the better method for the detection of knots. If mamma sonography is applied additionally to mammography the detection rate improves by circa 30 per cent.
Procedure:
Basics: The mamma tumor is the most common malignant alteration of the female breast. Besides the mammography (X-ray investigation) the mamma sonography is the most important examination for diagnosis. The sonography is applied in the early diagnosis of breast cancer. Its strong point lies especially in the distinction between liquid filled cavities (cysts) or alteration of tissue. By means of this method better targeting of the biopsy can be achieved. Immediately before the operation the ultrasonic investigation can show the precise position of the alteration and allows the surgeon to make a targeted operation. Especially after a cancer operation the remaining tissue can be controlled better by means of mamma sonography. Scar
First of all the breast model is examined by touching with the fingers. In this way both tumors can be found and the position can be determined roughly. By the 1 MHz probe an echogram of the breast is taken in the fixed region of examination. For this it is necessary to choose the device parameter so that besides the echo from the bottom mainly the echo of the tumor is measured. The adjustments and the alignment of the probe demand some experience from the student. After choosing suitable adjustments a B-image of the breast model is taken along a chosen line. If the adjustment of amplification especially of the TGC and the movement of the probe are well done, an ultrasonic brightness image of the tumor is clearly visible.
Results: For the evaluation of the ultrasonic image one has to keep in mind that the lateral local assignment may be inaccurate because the cross section image was taken hand-guided. Of course the precise position of the tumor can be palpated. On the other hand the depth and size of the tumor are determined only by the ultrasonic image. The image of the breast model can be somewhat irritating because the outer form of breast is displayed downwards. This echo is produced by the plain back of the model and therefore the distance to the surface is displayed, respectively. In the upper left area the tumor is recognisable as a weak reflection. However, the imaging of the sound shadow behind the tumor is more clear. The sound impedance of the tumor tissue is only slightly different from the surrounding tissue, however the attenuation is clearly higher. For the sound velocity of the B-image intentionally the double velocity of water (3000 m/s) has been chosen in order to enhance the depth resolution in the presentation. All depth numbers must be diveded by two. So the tumor exists in a depth of about 10 mm and has an extension of circa 20 mm.
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Ultrasonic experiments
MED03
Doppler sonography
Purpose:
Setup:
The goal of the experiment is to learn how blood flow measurements are made with Doppler ultrasound. A realistic arm model is used to show the differences between continuously (venous) and pulsatile (arterial) flow and between normal blood flow and a stenosis.
Ultrasonic pulse Doppler „FlowDop“ Ultrasonic Doppler probe Centrifugal pump “MultiFlow” Arm dummy incl. dummy fluid Ultrasonic gel
order order order order order
no no no no no
50100 50135 50130 50160 70200
essential in many areas such as determining reverse blood flow in the liver vasculature in portal hypertension. The Doppler information is displayed graphically using spectral Doppler or as an image using colour Doppler.
Procedure:
The pump is switched on and the speed is adjusted in a middle range (ca. 4000min-1). The mode is GK (continuously, venous). With the Doppler probe and coupling gel the arm model is scanned for a vessel with a significant audio signal. The flow in the spectral image is analysed for negative and positive components. The probe direction is then switched by 180°. Then the vessel is scanned for changes in the spectral image (stenosis) and the differences between the images of the „healthy“ vessel and the stenosis will be characterised. Lastly the pump is switched to P1 and P2 mode (pulsatil) the images are analysed and the pulse rate is determined.
Basics:
Doppler sonography uses the Doppler effect to assess whether structures (usually blood) are moving towards or away from the ultrasonic probe, and its relative velocity. By calculating the frequency shift of a particular sample volume, for example a jet of blood flow over a heart valve, speed and direction of this sample volume can be determined and visualised. Doppler frequency shift is the difference in ultrasonic frequency between transmitted and received echoes, i.e. the echo frequency minus the transmitted frequency. The Doppler frequency is proportional to the blood flow velocity. Doppler sonography is particularly useful in cardiovascular studies (sonography of the vasculature system and heart) and
Results:
Figure 1 shows a continuously (venous) flow with a mean Doppler shift of ca. -700Hz. The minus in the Doppler shift means flow away from the probe. Figure 2 is the spectral distribution with rotated probe. Flow towards the probe (the same Doppler shift, but positive). Figure 3 is the Doppler spectral figure of a stenosis. The differences to a normal (healthy) figure like figure 1 are: 1. A local increase of the maximum Doppler shift (maximum flow velocity). 2. A decrease of mean frequency and a broadening of the spectra. 3. An increase of reflux phenomenon (negative and positive parts of the spectra). Figure 4 shows the pulsatile flow of P1 with an pulse rate of ca. 90min-1.
Figure 1
Figure 3
Figure 2
Figure 4
66 Ultrasonic experiments
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Ultrasonic investigation with the eye dummy Purpose:
Setup:
In this experiment a typical application of A-scan ultrasound biometry in medical diagnostics used in ophthalmology is given. At an eye dummy all parts of the healthy eye are measured and correction calculations shall be done.
Ultrasonic echoscope GAMPT-Scan Ultrasonic probe 2 MHz Eye dummy Ultrasonic gel
order order order order
MED04
no no no no
10121 10132 10222 70200
Basics:
Ultrasound is used also in ophthalmology. Its largest importance lies in the area of biometry, in the measurement of distances in the eye. The distance between cornea and retina is very significant for the calculation of the characteristics of the artificial lens implanted to patients with cataract. Sonography is necessary in this case since the cornea or the lens are too cloudy for the use of optical methods. Investigations of the aqueous, vitreous humour and the thickness of the lens are nowadays often done with new methods of laser light or ultrasonic B-mode imaging. The given measured time of flight of the echoes of the A-scan can not be calculated as distance in a simple way, because of different velocities in the different media (cornea, lens, vitreous humour). Therefore a corrective calculation is necessary. Two velocities are given for the dummy: -lens: 2500 m/s, -humours: 1410 m/s. These values and the time of flight from the measured A-scan image shall be used to determine the distances with the help of the following equation: (1)
s=v
∆t 2
In medical diagnostics „averages“ are often used known from experience. This average velocity shall be calculated for the dummy with the following equation: (2)
v=
v1 (t1 + (t 3 − t 2 ) + v 2 (t 2 − t1 ) t3
Procedure:
Ultrasonic coupling gel is used to connect the probe to the cornea of the dummy. Slowly move the probe over the cornea to look for the optimal signals (2 large lens peaks and one smaller from the retina). After measuring the time of flight of the peaks the real distances can be calculated.
Results: The time of flight of each peak was measured and the averaged velocity was calculated with the equation (2). The result was adjusted to the A-scan device, it was switched to the depth scale and the depth of each peak was measured. velocities in m/s: (aqueous/vitreous humour)
1410 m/s
(lens)
2500 m/s
values:
front of lens
time in 10^-6 s
13,7
back of lens
retina 21,1
74,8
averaged velocity
1518 m/s
measured depth in mm
11,9
15,9
42,5
real depth in mm
9,66
18,91
56,77
thickness/ distance in mm
9,66
9,25
37,86
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Ultrasonic experiments
other product lines by GAMPT
Broadband PVDF Membrane Hydrophone Technical Specifcation
Calibration
• • • • • •
• • • •
Broad frequency range up to 140 MHz Very thin foil thickness (9 µm PVDF) High lateral resolution with small aperture size (240 µm) Electrode diameter of 210 µm Integrated differential preamplifier High signal to noise ratio
Very flat frequency response up to 40 MHz Maximum variation < +/- 6dB Thickness resonance at 105 MHz Usable range up to 140 MHz
Shielding electrodes
PVDF foil
Sensitive area
Electrodes
Membrane hydrophone construction
Frequency response of membrane hydrophone
Application
Sound field measurement systems
• Measurements of probe sound field with high resolution • Quality management for ultrasonic probes • Determination of acoustical output of medical ultrasonic devices
• • • •
Software for sound field measurement Scanning resolution up to < 10 µm PC controlled scanner system Inclusive ultrasonic transmitter and 70 db amplifier
Quelle: www.medical.siemens.com
Sound field of an annular ultrasonic probe
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68 Ultrasonic experiments
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other product lines by GAMPT
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Ultrasonic experiments
All products and experiments can be found and downloaded on our website
www.gampt.de.
70 Ultrasonic experiments
GAMPT mbH, Str. der Freundschaft 25, D-06179 Zappendorf, Germany, Tel. +49-34609-23683, Fax +49-34609-23684
www.gampt.de
Company profile GAMPT mbH was founded in 1998 by 5 physicists of the Medical Faculty of the MartinLuther-University Halle-Wittenberg, Germany. Ever since the company has evolved continuously into a competent partner in the field of ultrasound-based measurement technique. With their unique know-how our highly qualified employees develop and produce special measuring equipment for industry and medicine. Another important field of activity is the development and production of ultrasonic equipment for education. The performance profile of our company varies from circuit design over sensor construction and software development to the finished device. Maximum customer satisfaction is one of our particular objectives. To ensure this, our multilingual team keeps an intense and open contact to the customer and guarantees the highest quality of our products. We handle special customer needs very flexibly and offer unconventional solutions for complex problems. Our customers include international businesses, research organisations, universities and large clinics in Europe, North America, North Africa, Asia and Middle East.
References: CharitĂŠ Berlin, Germany Martin-Luther-University Halle-Wittenberg, Germany GOSH London, UK Freeman Rd. Hospital, UK King Faisal Hospital Riyadh, Saudi Arabia Fresenius Medical Care Inselspital Bern, Switzerland PTB, Germany Fraunhofer Institutes, Germany and many other universities, colleges, institutes and clinics worldwide.
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Ultrasonic experiments
Edition 1/2009 Copyright GAMPT mbH The pictures in this catalogue are performed for a better demonstration of the products. Modifications of form and colour are possible. The declared technical properties of the products are not touched. We reserve ourselves all rights concerning errors, translations, partial reproduction and photocopies.
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