Test & Measurement

From 50MHz to 100GHz, Bench-Top to Wristwatch Oscilloscopes Have Come a Long Way

In this story, we explore the latest features and kinds of oscilloscopes that play an integral role in effectively testing designs today. We also learn how new technologies in oscilloscopes are enabling test and embedded engineers to design better

ABHISHEK A. MUTHA

As an engineer, if you want to improve your design overall, effective testing is an integral part. However, it means possessing tools you can rely on and that can provide consistent results as per requirements.

Today, oscilloscopes come in numerous shapes and sizes—from as small as a wristwatch to pocket-sized and bench-top ones. They even have diverse bandwidths—from the entrylevel 50MHz to the massive 100GHz! Let us explore the new technologies, innovations and breakthroughs in the oscilloscopes domain that help our engineers design better.

From analogue to digital

From simple signal capture to complex time-domain signal analysis, oscilloscopes come with salient and contrasting functionalities. Oscilloscope manufacturers have augmented the automated capabilities and portability factor so that designers can accomplish swiftly and get more authentic measurements for increased productivity.

The invention of cathode ray tubes (CRTs) in the late 19th century was an important milestone for the birth of analogue oscilloscopes, and has changed the way of waveform representation, believes Srinivasa Appalla, managerproduct support & application, Rohde & Schwarz. However, he says, “The technological advancements in electronic designs have put new requirements on signal analysis which are not met by analogue scopes. Digital oscilloscopes, introduced in the 80s, are dominating the market now because of the ability of

Exciting innovations in the last one year 

Oscium’s iMSO-204 and iMSO-204L are mixed-signal oscilloscopes designed specifically for the iPhone, iPad and iPod. Highlights: 2 analogue + 4 digital channels, 50MSPS sample rate, 5MHz bandwidth, 200ns/div-10s/div Price: $399.97

Gabotronics’ Xminilab Portable is a small mixed-signal oscilloscope with an arbitrary waveform generator and protocol sniffer. Highlights: 2 analogue inputs, maximum sampling rate of 2MSPS, 200kHz analogue bandwidth, 8-bit resolution, 1MΩ 15pF input impedance, 256 buffer size per channel and input voltage range of -14V to +20V Price: $118   LabNation’s SmartScope is a 100MS/s open source oscilloscope for iPad, Android and PC. A must-have for every Arduino and Raspberry Pi developer. Highlights: 2x100MS/s 45MHz oscilloscope, 50MS/s arbitrary waveform generator, digital logic analyser at 100MS/s, digital waveform generator at 100MS/s, 200 waveforms/second data updates Price: $179

Gabotronics’ Oscilloscope Watch

Highlights: 2 analogue inputs, 4MSPS maximum sampling rate, 200kHz analogue bandwidth, 8-bit resolution Price: $150

digital signal processing, and respective analysis and documentation.”

Sumit Sharma, marketing manager-India, Good Will Instrument Co. Ltd. too believes, that with the rapid advancement of technology, the oscilloscope market has also been shifting from conventional analogue oscilloscopes towards digital storage oscilloscopes (DSOs). He says, “In contrast to analogue oscilloscopes, the major function of a DSO is to not only convert signals from analogue to digital but also store testing data, allow remote control and transmission of data through various interfaces.” But, he also believes, “Despite the strengths of DSOs, analogue oscilloscopes still play an important role of providing realtime signals and waveform display.”

Mixed-signal and mixed-domain

“As oscilloscopes have evolved from analogue to digital and from mixedsignal oscilloscopes to mixed-domain oscilloscopes, they have become even more valuable tools for analysing system performance or troubleshooting problems,” says Pamela Aparo, marketing manager-electronic test & measurement, Analog Devices Inc.

Embedded system designers require advanced testing capabilities to resolve their design issues, so mixed-signal oscilloscopes (MSOs) emerged in the

Are engineers ready to make the jump from knobs to a smartphone/tablet interface where they use their fingers to zoom in on a part of a waveform?

 “Manipulating the image on an oscilloscope by using touch-screen technology is a relatively easy jump for most engineers to make. A more difficult transition would be to use this kind of interface as the main screen to configure all the available functions in an oscilloscope with additional functions integrated.”—Pamela Aparo, marketing manager-electronic test &

measurement, Analog Devices Inc.

 “The new generation of engineers is smartphone savvy and enjoys working with the scope like an electronic gadget. Hence the user interface of the scopes is moving towards touch-screen operations.”—Srinivasa Appalla, manager-product support & application, Rohde & Schwarz  “The proliferation of consumer electronics with capacitive touch-screens and intuitive operation is creating a new set of user expectations that, as a test and measurement vendor, we are continuing to track and evaluate.”—David Farrell, general manager-mainstream oscilloscopes,

Tektronix

 “Yes. If a common man can zoom his images and watch closely on smartphones then engineers would surely appreciate and use it with warm welcome.”—Vivek Mantri, country

manager-industrial segment, Scientech Technologies Pvt Ltd

beginning of 2000, informs Sharma. He says, “There has been a growing need for detecting digital signals which are usually presented by two discrete voltage levels.” A logic analyser, which is the best fit for such digitalsignal measurements, has the benefit of multiple-channel input measurements, usually limited to two or four channels in oscilloscopes. He adds, “Nowadays, some system designers not only need an MSO but also an instrument which can afford to do frequency- and timedomain analysis simultaneously. So, a mixed-domain oscilloscope (MDO) is the latest trend.”

The continuously-evolving integration level of embedded designs drives further feature integration into oscilloscopes. Appala says, “Additional digital channels, as part of mixed-signal options, protocol-specific trigger and decode options are a few examples. The key requirement is a synchronised operation of such features for true system-level debugging.”

In the analogue to digital era, a significant number of digital designs came onto the analogue board, thus MSOs came to light about ten years ago. “The trend has evolved since, and mixeddomain oscilloscopes came into existence with Tektronix leading the charge. Today, mixed domain has moved to another level with the inclusion of wireless RF signals,” says David Farrell, general manager-mainstream oscilloscopes, Tektronix. He adds, “Analogue, digital and now RF signals are coming together to the embedded domain and creating significant changes on how work is done in designs houses and research centres, specifically with respect to analysing those signals in as short a time as possible.”

On a similar note, Aparo says, “Mixed-domain oscilloscopes offer similar benefits as mixed-signal oscilloscopes when an engineer needs to analyse signals in both the time domain and frequency domain—and these are useful in looking for problems that are caused by phase instability or phase offsets.”

Not everyone is into MDOs though. On the contrary, Sanchit Bhatia, digital applications specialist, Agilent Technologies India believes, MDOs are an attempt to add spectrum analyser capability to oscilloscopes. He says, “MSOs have not evolved to MDOs as yet due to lower specifications. In fact, in MDOs, the oscilloscope and spectrum analyser capabilities have gone backwards. Any general oscilloscope and any entry-level spectrum analyser have better specifications than today’s MDOs.” Supporting his view, he adds, “A stand-alone spectrum analyser and a stand-alone oscilloscope are a better solution than an MDO, as they offer full instrument capabilities and can be synchronised using external trigger, if the application so demands.”

Our fast-moving world needs to analyse data fast, and also on the move, informs Vivek Mantri, country manager-industrial segment, Scientech Technologies. He says, “Trending technology in telecom and RF segments needs data analysis to be extremely accurate in time to display waveforms, and in frequency to display signal spectra, where MDOs are a perfect choice.” However, he adds, “For most of the general-purpose requirements, analogue oscilloscopes are sufficient.”

Handheld, PC-based, phone and even a wristwatch scope

Oscilloscopes have evolved from the typical bench-top instruments to as small as a wristwatch, providing flexibility and an array of choices. Mantri defines today’s generation as tech-savy, that is more comfortable with touch screens and USB data transfers. He says, “They want their oscilloscopes to be handheld, with an easy interface, and prefer data transfers through SD cards. Different user segments will find analogue, MSO or PC-based instruments useful, depending on their usage.” Although, he maintains, no single technology can be suitable for all kinds of applications.

Today’s handheld oscilloscopes range from 20MHz to 500MHz in bandwidth, with sampling rates from 500Msa/s to 5GSa/s, and mostly come with LCD displays. Typically, with two channels, these are ideally suited for use by hobbyists, students, technicians and anyone else looking for an easyto-use, affordable, single-channel PC oscilloscope.

PC-based oscilloscopes, complemented with software, provide bandwidth signal analysis anywhere between few tens of MHz to as high as 20GHz. These USB, modular devices typically have one, two, four or even eight channels with USB 2.0 or USB 3.0 interface, depending on the model. Some of them are even loaded with memory capacity. The software provided with these instruments is used to transfer instrument set ups, meas-

urement data and images, and mostly favours the Windows operating system. But some oscilloscope makers are providing support for Linux, Mac OS X and even for Raspberry Pi.

Interestingly, apart from these, engineers can now perform analysis on their iPhones and on small devices such as a wristwatch scope (see the box titled ‘Exciting innovations in the last one year.’)

There are various other pocketfriendly oscilloscope devices available in the market for engineers. At the end of the day, it all depends on the engineer’s preference, purpose and understanding of the devices’ limitations. People will either love it or remain nonchalant with these innovations.

Knobs vs smart touch

Today, smart touch interfaces can be used to define areas where you want the oscilloscope to trigger. These interfaces are fully configurable. Traditional analogue scopes were designed for operation using dedicated knobs and buttons. However, the latest digital scopes incorporate touch-screen displays, enabling new operating concepts and enhancing ease of use, informs Appalla. He says, “As the model acceptance heavily depends on the user’s taste and experience, it is advantageous if instruments support multiple ways of operation—dedicated knobs, USB keyboard/mouse and touch-screen interface. An intuitive operating interface helps users to navigate faster and reduces time in setting up, executing and documenting measurements.”

Oscilloscope makers keep adding features to their instruments based on user demand for more signal analysis. “Good touch-screen implementations support drag-and-drop functionality for organising the display with multiple waveform diagrams and for selection of predefined operations. Other innovative user-interface concepts include colour-coding of buttons and knobs for guiding the user,” adds Appalla. In future, more touch-screen functionality, which is popular in consumer devices, will follow.

Sharing her personal experience, Aparo notes, “Although knobs and buttons are somewhat comforting when I start working with a new oscilloscope, I have to say that moving away from traditional knobs has made it easier to automate certain tests, and it has made it possible to save common configurations. The learning curve for using a new oscilloscope with multiple menu levels is higher than when purely analogue oscilloscopes were the only option—but this is also because the new oscilloscopes can do so much more.” She adds, “Obviously, having USB interfaces on oscilloscopes makes it easier to store test results and import them into other programs for writing reports or presentations.”

Although oscilloscope screens are evolving to capacitive touch interfaces with multi-touch capabilities that provide zoom capability and analysis capability with great ease, Bhatia believes that common traditional knobs like channel scaling, offset and trigger modes, to name a few, are being retained as the engineers are used to operating scopes with these knobs.

As the touch has been successfully implemented in mobile systems, more electronic devices will feature this technology. Sharma says, “In this fashion, a traditional hand-held oscilloscope is being upgraded to the full touch-screen hand-held scope as a next-generation transition. This may minimise the gap between high-end and low-end scopes and bring the whole new experience of using oscilloscopes to engineers.”

From 50MHz to 100GHz

An apparent factor when choosing an oscilloscope is bandwidth. And, incidentally, the biggest impact on the price of a scope is its bandwidth and the number of analogue samples per second that it can read. For error-free results, most engineers know that the samples per second figure should be at least three to five times higher than the bandwidth. Engineers, typically, prefer entry-level and mid-level oscilloscopes.

But almost a year back, Teledyne LeCroy had demonstrated a 100GHz real-time oscilloscope targeting applications such as CEI-25/28, CEI-56, optical coherent modulation communication systems, defense and radar applications, emerging 10-32Gb/s serial data technologies, 100GBASE-R Ethernet, SAS12, PCI Express Gen4, Thunderbolt and next-generation USB. Agilent Technologies had also introduced real-time oscilloscopes with 63GHz true analogue bandwidth in 2012. So, what’s the significance of such extremely-highbandwidth oscilloscopes?

High-speed serial standards, such as PCIe Gen4, MIPI MPHY and Fibre Channel, work at speeds beyond 10Gbps, and require high bandwidth to capture the signal content, informs Bhatia. He says, “With the adoption of high-speed serial standards, bandwidth demands on oscilloscope keep increasing.” On a similar note, Aparo says, “Higher-bandwidth oscilloscopes are important in measuring the performance of higher-speed data links like USB 3.0 and JESD204B interfaces. They are also needed in the development of new high-speed digital interfaces and fibre optics.”

Major significance for this kind of breakthrough is due to trends right from Telecom, RF, space technologies, to high-end medical electronics gadgets used in telemedicine, informs Mantri. However, he says, “Generalpurpose, lower-frequency oscilloscopes will continue to lead the market for their ease of use, lower cost and versatility. They are easy to service and find wide applications in production, service, testing and troubleshooting.”

Trends and tools that help

Continuous integration at design level raises new challenges for test and

Notable changes in oscilloscopes in last one year  USB 3.0 in PC-based oscilloscopes  Integration of multiple instruments in one oscilloscope  Smart touch-screen interface  Support for operating systems like Linux and Mac

debugging. Embedded design is the buzz word today, informs Appalla. He says, “Former truly-isolated functional blocks and circuit components now get closely integrated on circuit board or even multi-chip level. For system debugging, a time-correlated analysis of analogue signals, such as switched mode power supplies or D/A converters, as well as digital signals of various communication and programming interfaces is required. Additional complexity is given by protocol-based interfaces or integrated RF components.”

The user requirements, as mentioned above, are drivers for standard oscilloscopes. “Debugging of protocolbased interfaces, such as I2C, SPI or CAN, is supported with trigger and decoded options. Often a bandwidth of 1GHz is required, not only because of faster digital signals but also driven by fast edges of clock signals or power supply switching. A suitable sample rate of 5Gsample/s and a minimum acquisition memory of 10Msample enable a signal acquisition with high resolution over a long observation period,” adds Appalla.

In general, the trends in oscilloscopes are focused on helping engineers answer their questions faster. In addition to integrating logic analyser and spectrum analyser functions in the MSO and MDO classes of instruments, another trend is the integration of signal sources in the oscilloscope, informs Aparo. She says, “This function can range from a simple sine-wave or square-wave generator to something as complex as a multichannel arbitrary waveform generator that allows users to create modulated signals. This trend of integrating more features and functions into the oscilloscope helps engineers get answers more quickly, because it provides all the needed tools in a single platform.” An example of this kind of integration can be witnessed in Tektronix’s MDO that boasts of six instruments built in one, namely, oscilloscope, spectrum analyser, logic analyser, arbitrary/function generator, protocol analyser and a digital voltmeter.

Oscilloscopes also increasingly offer better bandwidth, more analysis capabilities and better hardware specifications, informs Bhatia. He says, “Analysis capabilities offered today include variety of protocol analysis tools, compliance applications and more mathematical functions. Tools such as AC calibration of probes, deembedding and equalisation offer better reproduction of the signals on the scopes.”

New and still not so common with oscilloscopes is the operation in the frequency domain. But users request this functionality, informs Appalla. He says, “They want, for example, to debug EMI problems caused by power supplies, fast edges or touch-screen emission.”

Technologies for tomorrow

One of the new technologies developed for high-bandwidth scopes is indium phosphide (InP) semiconductors, informs Bhatia. He says, “New technologies are developed by Agilent labs (a research organisation within Agilent), which focuses on higher integration, low-noise front ends and high-speed designs.” He adds, “InP semiconductors have very low noise and high transistor-breakdown voltage at high frequencies. Thus, they can handle higher voltages at high bandwidths. This helps design engineers make high-bandwidth measurements very accurately and with great confidence.”

Targeting embedded design engineers, Tektronix delivered advanced 802.11 WLAN test solutions to its mixed-domain and performance oscilloscopes. Engineers can use tools for integrating 802.11 a/b/g/j/n/p/ac WLAN connectivity into their product designs. The new WLAN solutions address the growing demand toward integrating Wi-Fi in everything from home appliances to industrial equipment.

Many of the new technologies being developed are also software improvements that make it easier for engineers to test or simulate their systems more quickly. Aparo says, “This is often found in larger markets like wireless communications or automotive radar, where there is a large pool of engineers who are working on these applications around the world and their needs converge on common requirements or published standards.” Talking about how it would help a design engineer, she adds, “Improving software for oscilloscopes can reduce the time it takes a design engineer to understand what is not working, or verify the performance of a new platform. By pre-loading common tests or waveforms into the software, engineers know there is consistency in the information they are gathering, and this makes it easier to collaborate with other team members.”

High-end test and measurement requires high-end semiconductors to make them work efficiently. Mantri says, “So, support on making the semiconductors application-specific from respective vendors can create a big wave in this market. Compact USB digital oscilloscope will be a dream come into reality for service engineers on field at an affordable cost.” 

Major contributors to this article

David Farrell general managermainstream oscilloscopes, Tektronix

Pamela Aparo

marketing managerelectronic test & measurement, Analog Devices Inc.

Sanchit Bhatia

digital applications specialist, Agilent Technologies India Pvt Ltd

Srinivasa Appalla

manager-product support & application, Rohde & Schwarz

Sumit Sharma

marketing managerIndia, Good Will Instrument Co. Ltd

Vivek Mantri country managerindustrial segment, Scientech Technologies Pvt Ltd

The author is a senior technical correspondent at EFY

Budget-Friendly Oscilloscopes

digital oscilloscopes, being expensive, have always been out of reach for many. but this doesn’t make them less desirable. Fortunately, test and measurement companies have sensed this situation and started developing low-priced oscilloscopes with reasonable quality and features. so we now have several wonderful low-budget options. Let us take a look at some of them

Ankit GuptA

Agood oscilloscope is an indispensable tool for you if you are seriously into electronics. The oscilloscope helps you check the functioning of electronic circuits better. With advancements in technology, electronics designing, testing and even repairing has become much more challenging than before. Engineers thus require advanced tools to solve measurement challenges quickly and accurately, and a digital storage oscilloscope helps them do just that. But, due to its high price, this equipment has always been out of reach for most individuals.

The strong desire of the engineers to possess a good oscilloscope has led companies such as Tektronix, Agilent and Teledyne LeCroy to introduce low-priced oscilloscopes that promise reasonable acquisition quality and performance. Generally, these look like a standard oscilloscope with integrated display for viewing the acquired signal as shown in Fig. 1.

Another low-cost solution comes from companies such as Digilent, Virtins Technology, Link Instruments, Parallax Inc. and Velleman Inc., which uses processing power of a computer and its monitor to display the acquired signal. These solutions are becoming more popular as they are compact yet show the signal on a larger display of a computer for better analysis. Some of these are even multifunctional, with additional functions of waveform generator, logic analyser, DC supply and multimeter. Fig. 2 shows such a system.

Next are the small pocket-size oscilloscopes that can be highly useful for field engineers. Most of these are low-priced. Though their accuracy is not as good as the previous options but these are good enough for basic analysis. Fig. 3 shows a pocket-size oscilloscope.

There are also various open source do it yourself (DIY) oscilloscope designs available on the Internet. You can build these systems yourself and use for basic test and measurement. Such systems are very useful for students as they learn a lot while building their own oscilloscope and then use it with better confidence. Fig. 4 shows such a system.

There are so many options avail-

Fig. 2: An oscilloscope that shows signal on a computer’s screen

Table I Some low-budget Oscilloscope Options

Specifications Tektronix TbS1052b-eDU agilent DSO1052b Gwinstek GDS-1052-U Rigol DS1074Z

Teledyne leCroy 940-WaVeaCe1001

Bandwidth 50MHz 50MHz 50MHz 70MHz 40MHz Sample rate 1.0GS/s 2.0GS/s half channel interleaved, 1 GS/s all channels 250MS/s maximum 1GS/s 1GS/s (interleaved)

External trigger Yes Number of channels 2 Yes Yes Yes 2 2 4 2

Automated waveform measurement Yes Yes Yes Yes Yes

Waveform math Yes, FFT Yes, FFT Yes, FFT Yes, FFT

I/O interfaces USB, GBIP (optional) Display size 17.8cm (7 inches)

Overall dimensions 326mm x 158mm x 124mm (approx.) USB USB USB USB

14.7cm (5.7 inches) 324.6mm x 157.8mm x 129.2mm 14.7cm (5.7 inches) 17.8cm (7 inches) 17.8cm (7 inches)

310mm x 142mm x 140mm 313.1mm × 160.8 mm ×122.4mm 163mm x 313mm x 115.8mm

Fig. 3: A pocket-size oscilloscope

able for each type of oscilloscope. But before looking at these options to evaluate which one suits your requirement, you need to understand their specifications. You can have correct measurements only when your oscilloscope’s specifications support the range of the signals you are trying to measure. Some of the important specifications are:

Bandwidth. It determines the maximum frequency signal that the oscilloscope can accurately measure. The accuracy decreases with increase in signals’ frequency. The bandwidth mentioned in the datasheet (say, 100MHz) is actually the frequency at

Fig. 4: A DIY-type oscilloscope

which a sinusoidal input is attenuated to 70.7% of its true amplitude. Beyond this frequency the oscilloscope cannot support reasonable accuracy. To decide how much bandwidth you need, find out what would be the range of frequencies you would need to measure. Once you know the frequency range, just use the ‘five times’ rule, that is, multiply the maximum frequency by five and you have the bandwidth that you need to accurately measure those signals.

Rise time. Rise time is the time taken by a signal to change from a specified low value to a specified high value. Typically, these values are 10% and 90% of the step height. As a thumb rule, similar to bandwidth, the rise time of the oscilloscope should be less that 1/5 of the fastest rise time of the signal to accurately measure it.

Sample rate. Sample rate refers to how frequently a digital oscilloscope takes a sample of the signal. The faster an oscilloscope samples, lesser the details lost while reconstructing the signal. In order to accurately reconstruct a signal and avoid aliasing, the Nyquist theorem states that the signal must be sampled at least twice as fast as its highest frequency component. This theorem assumes an infinite record length and a continuous signal, but no oscilloscope can offer infinite record length. Therefore sampling at only twice the rate of the highest frequency component will not be sufficient.

The sampling rate that you might require to accurately read your signal will majorly depend on the method used for reconstructing the signal, also called interpolation. For accurate reconstruction using sin(x)/x interpolation, sample rate should be at least 2.5 times the highest frequency component of your signal. Using linear interpolation, the sample rate should be at least 10 times the highest frequency signal component.

Record length. The oscilloscope cannot store infinite number of samples as assumed by Nyquist equation. Record length determines the time that can be captured by each channel of the oscilloscope.

Time captured = Record length/ Sample rate

Normally, an entry-level oscilloscope comes with 2k to 2.5k points, which is more than enough. In general, greater record length is better.

Table II Some PC-based Oscilloscopes

Manufacturer Model bandwidth Sample rate

Dynoninstruments ELAB-080 60MHz 80MS/s

Multifunction

Yes

Bitscope BS50

70MHz 40MS/s Virtins Technology VT DSO-2820R 80MHz Yes

Yes

Link Instruments MSO-19

60MHz Repetitive mode: 1GS/s Yes Single shot: 200MS/s Jyetech DSO 094 (Dual channel) 10MHz 50MS/s No Parallax PropScope USB Oscilloscope 25MS/s Yes Picotech PicoScope 2104 10MHz Repetitive mode: 1GS/s; Single shot: 50MS/s Yes

Dynoninstruments S2X100 50MHz 100MS/s

Yes Easysync DS1M12 250kHz Repetitive mode: 20MS/s Yes Synchrotech USB-SCOPE50 75MHz 1GS/s No

Table III

waveform, but waveform capture rate refers to how quickly

Some Pocket-Size Oscilloscopes an oscilloscope captures a waveform. The oscilloscopes with better waveform capture rate capture fast transients better.

Probe specifications.

Probes’ specifications are as important as that of oscilloscope. The probe’s bandwidth should match the bandwidth of the oscilloscope. Here also the five time thumb rule works perfectly. The probe will be in direct contact with the circuit and To capture and debug serial bus you should not overload it. Otherwise, the will need record length as high as measurements will not be correct. Re1M points. sistive loading greater than 10M-ohms

External trigger. External trig- and capacitive loading less than 10pF gers allow you to stabilise repetitive is acceptable for a probe. waveforms and make them appear static on the display by continuously Integrated display type displaying the same section of the oscilloscope input signal. Generally, oscilloscopes Table I show some low-budget are available with edge and pulse- integrated-display oscilloscopes width trigger. But advanced trigger- available from different manufacturing options like A and B sequence, ers, including their brief specificavideo, communication (CAN, SPI, tions. The bandwidth you can get in etc) and logic triggering can help you this budget will mostly be less than debug faster. 100MHz, which is more than enough

Waveform capture rate. Sample for basic analysis and testing, if you rate indicates how fast the oscilloscope go by ‘five times’ thumb rule dissamples the input signal within one cussed earlier. And you get a lot of

Manufacturer Model bandwidth Sample rate

Jyetech DSO 094 (Dual channel) 10MHz 50MS/s Velleman APS230 2 x 30MHz 240MS/s

Velleman HPS10 2MHz 10MHz Velleman HPS50 12MHz 40MHz Velleman PPS10 2MHz 10MS/s uni-trend UT81B 8MHz 40MS/s Seeedstudio DSO Nano v2 0-200kHz 1MS/s Seeedstudio DSO Nano v3 0-200kHz 1MS/s advanced features of expensive oscilloscopes, such as math functions and USB storage, also with these oscilloscopes.

Being mostly compact in size, these can be used as bench-top oscilloscopes and also moved easily, if required. Their display size ranges from 12.7cm to 17.8cm (5 to 7 inches), which is enough for proper viewing. But some vendors boast of utilising the same space more efficiently with advanced features like auto-hide menu panel and sectional zooming.

PC-based oscilloscopes

A PC-based oscilloscope is normally a small piece of hardware that is attached to a computer to acquire the signal and show it on the computer’s display. In most cases the power supply too is derived from the computer’s USB port, which makes them very handy and easy to carry along. A lot of multifunction options are also available, such as additional signal generator, logic analyser, multimeter, 5V DC supply, digital I/Os and spectrum analyser.

The multifunction oscilloscopes are perfect for students and hobbyists, who do not require higher accuracy but need all the tools at one place. Availability of the signals on a bigger display is also a treat for the eyes. The window software for these oscilloscopes provide analysis and storage tools. Table II shows some of the PC-based systems available in the market.

Pocket-size oscilloscopes

Pocket-size oscilloscopes are easy to carry along and normally work on battery. The frequency range that you get in these oscilloscopes is limited. Some expensive ones do support signals in megahertz range but the low-budget ones are normally for kilohertz range only. So these cannot be used for debugging highfrequency signals; they only support basic testing and are very handy in field work.

Some of these also come with wireless connectivity, such as Bluetooth. Using them you can view the signals remotely within a defined distance. There are a few that you can connect to you Android device and view the signals wirelessly. Table III shows some of the pocket-size oscilloscopes from different vendors.

DIY-type oscilloscopes

Lot of designs are available on the Internet to build oscilloscopes yourself and use them for basic testing. In most cases, complete designs including schematic, layout and source code are available. Their performance, however, will depend on the quality and proper assembly of the components.

DIY-type oscilloscopes are mainly microcontroller based. The most popular microcontrollers for oscilloscopes belong to AVR and PIC series. Their frequency range also is not very high. Some of them display the

Table IV Some DIY-Type Oscilloscopes

Model bandwidth Sample rate Website link

AVR DSO 10MHz 50MS/s http://www.ulrichradig.de/home/index.php/avr/avr-dso

DSOA Mk3 5MHz 20MS/s http://alternatezone.com/electronics/dsoamk3.htm

eOscope 20MHz 40MS/s http://www.eosystems.ro/index.php/projects/eoscope

06201P 1MHz 5MS/s http://www.jyetech.com/Products/LcdScope/eDSO062.html

PIC12F675 Oscilloscope http://www.semifluid.com/2006/01/31/pic12f675-oscilloscope/

PPMScope 500kHz 1MHz http://jonw0224.tripod.com/ppmscope.html

SX28 http://www.sxlist.com/techref/ubicom/sxoscope/index.htm

signals on a computer monitor while others have integrated LCD displays. Those using computer monitor for display are more comfortable than those with integrated displays. Table IV shows some of the DIY-type oscilloscopes.

From all the above types and options, choose the one that suites your taste and requirements. All the oscilloscopes offer reasonable quality, including the DIY ones. However, one from a reputed manufacturer is more likely to give accurate measurements and performance.

It is only the beginning; we are likely to see a lot of better and cheaper options in future. 

The author is a technical editor at EFY