Test and Measurement Handbook 2020 by WTWH Media LLC

Detecting counterfeit integrated circuits without a microscope Page 28

Basics of monitoring vs. testing in current, voltage and power Page 44

JUNE 2020

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Will your Good Samaritanism in the pandemic buy you a lawsuit? IF YOU ARE ONE OF THE INDIVIDUALS voluntarily spending your time on technology to help abate the COVID 19 pandemic, consider the experience of the vacuum cleaner company Dyson in the UK. Company founder James Dyson estimates his ﬁrm spent about $25 million and about 10 days to develop a respiratory ventilator that would help ﬁll a projected shortage in that country. While waiting for regulatory approval to produce 10,000 of the machines, Dyson got word from the UK government that his ventilators wouldn’t be needed after all. Dyson has reportedly said he didn’t mind the expense and time put into the project. But he might end up being lucky his hastily conceived ventilators never reached the market: At least he won’t be sued for his trouble. As the smoke clears from the initial pandemic battles, federal politicians are now talking about shielding companies from liability stemming from their actions during the crisis. But the discussions so far center on workers at U.S. businesses. Employers fear a wave of litigation when returning workers start getting sick from the coronavirus. So there has been a push for legislative immunity forcing plaintiffs to show that businesses were grossly negligent or reckless in exposing their workers and customers to the virus. However, none of these discussions extend to manufacturers making health care equipment in war-effort conditions. Some states have proposed expanding liability protections to manufacturers aiding in the crisis, but there has been no real action on that that front. On the other side of the issue are plaintiffs’ lawyers who claim immunity shields remove incentives to keep employees safe. But there is some dark humor in the legal profession that perhaps expresses their position more succinctly: Every corpse has a lawyer. Manufacturers have reason to be concerned about legal troubles. The U.S. Food and Drug Administration normally requires that most new medical devices undergo lengthy laboratory and animal testing to answer basic questions about safety. However, the medical devices being devised during the coronavirus pandemic aren’t getting this kind of scrutiny. Late in March, the FDA issued an Emergency Use Authorization (EUA) that eliminated a need for manufacturing facilities to follow current good manufacturing practices (CGMP), including quality system requirements, when

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making ventilators. Suspending the CGMP practices-- which typically involve a significant amount of procedure documentation and record keeping--allowed non-medical manufacturers such as Ford and GM to begin ventilator production. The EUA also allowed commercially available bag resuscitators and other devices to be modified in ways that allow them to fill in as ventilators. This isn’t the first time the FDA has relaxed its medical device regulations. In the past, it has allowed equipment to forego clinical testing if it could be proved to be “substantially equivalent” to similar devices already commercially available. But the FDA has taken flak for these policies because they have occasionally led to approving equipment for sale that later underwent significant recalls due to various design and production issues. And when it comes to respiratory ventilators, the evidence is that even equipment manufactured under normal conditions can have problems. That was the reason the UK recently decided not to use ventilators obtained from China which, UK officials said, were prone to providing an unreliable and varying supply of oxygen. All these factors constitute lawsuit fodder if well-intentioned manufacturers don’t get legal protection. Absent such protection, we may see yet-another example of the old adage that no good deed goes unpunished.

LELAND TESCHLER | EXECUTIVE EDITOR eeworldonline.com

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CONTENTS TEST & MEASUREMENT HANDBOOK | JUNE 2020

18 32

Will your Good Samaritanism in the pandemic buy you a lawsuit?

Capabilities of modern data recorders Fast sampling rates and long recording times make data recorders useful for documenting signal qualities that ordinary test equipment can easily miss.

Nothing fishy about portable scope apps

The complexity of wireless receiver tests

Verifying 5G with OTA testing

The crowded spectrum of today’s RF environment puts a premium on quantifying the performance of radio receivers.

The 5G realm puts a new emphasis on making measurements without hardwired connections.

Work-at-home tools: PC-based instruments address demanding applications

FIPS 140-2 security testing for wireless medical devices Design engineers should be aware of several testing issues surrounding encryption standards designed to protect data from bad actors.

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Testing regimes for the new frequencies and features of 5G Measurements taking place in pre-commercial 5G network trials provide new insights and overcome uncertainties before the technology’s formal launch.

Detecting counterfeit integrated circuits without a microscope Curve-trace testing can reveal whether an incoming batch of ICs are bogus without resorting to destructive inspection measures.

Researchers get a charge out of measuring eels with battery powered oscilloscopes.

Advanced technology now lets budget-priced instrumentation handle tasks once requiring specialized and pricey test gear.

Work-at-home instrumentation

Monitoring heart-rate variability for better athletic performance

The rise in social distancing has fostered a need for professional-grade test instruments that function as well at home as in the lab.

Sensors and sophisticated algorithms together deliver check heart-rate variability and other exercise metrics.

Basic test instrumentation and its role in measurements It can be helpful to understand the differences between common test gear used for bench-top development tasks.

Basics of monitoring vs. testing in current, voltage and power Industrial measurements often must take place via specialized transducers sized specifically for the current and voltage swings involved.

6 • 2020

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Capabilities of modern data recorders

JAMIE PEDERSON | B&K PRECISION CORP.

Fast sampling rates and long recording times make data recorders useful for documenting signal qualities that ordinary test equipment can easily miss.

es is

Lo g

n ra i

nc e

e ug ga

e ag

C ur re n

DATA RECORDING INSTRUMENTS

Vo lt

Te m

pe ra t

ur e

Common data recorder inputs

have a long history that dates back to the 1800s when Charles Babbage incorporated an instrument into a rail car to record over a dozen parameters. Babbage described his prototype as a roll of paper one-thousand feet in length that slowly unraveled itself upon a long table. The model had roughly a dozen pens connected with a bridge crossing the center of the table, each marking its own independent curve. Technology has since advanced to the point where we are now capable of storing an extensive amount of data on a small memory device. Older data recorders tended to be limited to recording only signals having values that changed relatively slowly. That was because they had response times that were limited by the electromechanical pen and paper system used to archive data. Today, such limitations are no longer in place, particularly for the latest generation of recorders. Today’s data recorders feature fast sampling rates, large internal memory, touch displays, and a wide range of input capabilities. Data recorders can replace several instruments and provide additional options such as thermal printing and communication bus analysis. It is not unusual for data recorders to feature the same kind of triggering mechanisms available on scopes, including triggers based on the leading and falling edges of the signal being recorded. Additionally, it is relatively easy to ﬁnd recorders providing the same kind of analysis available on specialized instrumentation such as power line quality monitors. X-Y displays as long found on oscilloscopes are also available on data recorders. Digital multimeters are used primarily for measuring voltage, resistance and current. Data recorders, on the other hand, are capable of measuring the same parameters but can also monitor temperature, humidity, vibration, strain, revolutions

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Common signals measured with data recorders include those from strain gauges and temperature sensors, as well as voltage, current, logic, and variable resistance parameters.

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DATA RECORDERS Environmental data monitoring Environmental chamber Temperature

A typical configuration for a DUT sitting in an environmental chamber. The data acquisition system monitors the DUT and environmental sensors.

Barometer Humidity

DUT

per minute (rpm), to name just a few entities. Unlike typical DMMs, recorders excel in performing these measurements on multiple channels simultaneously. The data can be analyzed on-screen with built-in cursors to select speciﬁc waveform details, or the data can be transferred to a computer. Recorders also support more complex operations such as writing of custom equations for performing mathematical calculations based on real-time data coming in from two or more channels. Digital storage oscilloscopes (DSO) have become a widely used means of capturing and storing waveform data and have evolved to include triggering capabilities along with fast sampling intervals. In comparison, data recorders offer more channels, greater vertical

Temperature Current Voltage

resolution, and more memory which allows recording and comparing of more signals over a longer period of time. When using a DSO, the trigger event might be missed, but a data recorder will capture it because it is recording continually. All B&K Precision recorders feature a pre-trigger option to set a percentage of time to capture before the trigger event, ensuring valuable data is not lost. Users who must acquire data for longer periods of time across multiple channels or from a variety of input signals will beneﬁt from using a data recorder. These instruments have been designed to enable direct input and measurement of a wide variety of voltage, current, frequency, temperature, strain gauge, and logic signals with voltage inputs ranging

Data recorders in automotive applications EV charging Current / voltage

Portable data recorders often carry out motor vehicle measurements of exhaust temperature, wheel speed, engine temperature, strain/ vibration levels, and current/ voltage levels associated with EV charging.

Vibration / strain

Engine temperature

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from millivolts to kilovolts. This allows a single instrument to simultaneously measure small sensor signals and high-voltages, greatly simplifying data acquisition compared to schemes requiring multiple instruments. A common application for data recorders is in environmental testing as with the monitoring of parameters such as temperature, humidity, wind speed and direction, as well as barometric pressure at a weather station. These environmental tests may involve monitoring the voltage and current of the device under test placed in an environmental chamber to verify how the DUT responds to changes in environmental parameters. Recorders are also widely used in the automotive industry. Motor vehicles contain numerous sensors, electronic controls and systems which the instrument can monitor simultaneously. Key measurements include voltage and current, force, pressure, stress/ strain, speed, and temperature. Many recorders offer the additional capability to monitor and analyze trafﬁc on the CAN or LIN bus, which are widely used interfaces in this industry. Data recorders are capable of monitoring systems in industrial settings. Portable recorders aid in preventative maintenance. They can be used to monitor voltage, current, temperature, strain, and vibration signals of industrial equipment, to detect abnormalities,

Wheel speed

Exhaust temperature 6 • 2020

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TEST & MEASUREMENT HANDBOOK Data recorders can provide many of the same functions found in specialized instruments such as power quality analyzers.

and to record data that can allow accurate predictions of component failures for scheduling maintenance conveniently rather than stopping processes for repairs.

IMPORTANT SPECIFICATIONS When considering data recorders, the highlevel speciﬁcations of interest include: • • • • • •

Number of input channels Measurement parameter types (i.e. voltage, current, frequency) Minimum and/or maximum input voltage Sampling rate Memory size Modes of operation

The number of channels is a trade-off with portability. As the number of channels rise, so does the weight of the unit. The type of measurements and voltage input ranges are generally not ﬂexible – they are what they are

for particular applications. But sampling rate and memory size require more consideration. Although a faster sampling rate may seem desirable, it will reduce maximum recording time, given a ﬁxed memory size. For this reason, it is important to well understand the nature of the signals to be captured when selecting a data recorder. Many data acquisition systems have multiple modes of operation: One mode for recording over longer periods of time at a lower sampling rate, another mode for recording at a higher sampling rate over a shorter time to capture intermittent events. Additionally, some recorders provide the ability to synchronize to an external time base such as IRIG (Inter-range instrumentation group) time codes or GPS signals. It is useful to consider speciﬁc recorders as a way of understanding the range of equipment available in this area. The DAS220BAT and DAS240-BAT data recorders are

Double triggering MEMORY

lightweight and portable with built-in batteries that provide up to 15 hours of continuous recording from 10 to 200 channels with a sampling interval of 1 msec, 16-bit vertical resolution, and 100 Vdc maximum input voltage. The long battery life makes this recorder useful for process-control applications where power sources are unavailable. The DAS30/50/60 series offers two, four and six channels, with a built-in battery for up to 9.5 hr of recording time and an optional thermal printer. This series offers a sampling interval of 1 µsec in memory mode, built-in SSD up to 64 GB as well as a 500-V maximum input. A power analysis application included with this series allows for recording and analysis of single or three-phase power networks. This series of recorders is a good ﬁt for industrial applications that involve high voltages and faster sampling rates. The newest addition is the DAS1700, a conﬁgurable data acquisition system. This instrument features four types of measurement boards that can be installed in any combination of up to three in the base unit of the recorder or up to six with an optional expansion. These boards include a universal input board with a maximum voltage

Data recorders now incorporate triggering options that mimic those of oscilloscopes. One example is double triggering where the recorder can capture the leading edge or trailing edge of a signal.

MEMORY Trigger

Trigger - 50%

+ 50% Start of buffering

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DATA RECORDERS Data monitoring in electric motors

HIGH PERFORMANCE CONNECTORS & CABLE SOLUTIONS

Vibration

Temperature RPM Data acquisition system

Data acquisition

of up to 500 V and six channels, a high-voltage systems monitor board for up to 1,000 V and six channels, a electric motor strain gauge board with six channels, and a parameters that multiplexed board with 12 channels. typically include The DAS1700 is capable of streaming vibration and measurement data directly to the internal solidtemperature as well state drive at a 1 µsec sampling interval and as motor speed and can record continuously for extended periods acceleration. of time, with the recording length only limited by the size of the SSD. This instrument is also capable of recording two files simultaneously. When recording starts, the low speed file captures data at a lower sampling rate for a long period of time. An event trigger starts recording to the high-speed file which captures data at a high sampling rate for a shorter period of time. This ensures that not only is the event captured, but the state before and after are captured as well while maximizing memory space. The DAS1700 expands the measurement range to a maximum input of ±1,000 Vdc or 1,000 Vac. It also includes the power analysis tool of the DAS30/50/60 series along with a function editor. This user interface allows building custom functions to make calculations on data coming in from multiple channels. The result is displayed on a separate virtual channel for easy analysis. Factory options like CAN/LIN and GPS/IRIG timing further expand the capabilities. This data acquisition system is capable of measuring signals ranging from small sensors to large electrical systems and used in aerospace, industrial, automotive, and energy production applications.

REFERENCES

B&K Precision Corp., www.bkprecision.com/

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® 9

1-800-444-5366 www.lemo.com

TEST & MEASUREMENT HANDBOOK Crampton and the BBC film crew look for electric eels in the Amazon. | Will Crampton

Nothing fishy about portable scope apps Researchers get a charge out of measuring eels with battery powered oscilloscopes.

NEXT TIME YOU ﬁnd yourself swimming around with electric eels, try grabbing one and then put the leads of a battery powered oscilloscope on its head and tail. According to University of Central Florida zoology professor Will Crampton, you’ll probably measure a voltage in the 700-V range. Crampton and his associates went to the rivers of the Amazon to check out eel voltages. “Capturing eels out of the wild takes a lot of patience,” says Crampton. His technique for ﬁnding test subjects consisted of either setting up un-baited traps that eels can’t easily get out of, or using baited hooks to lure the eels from hiding.

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Crampton’s procedure for measuring the electricity in eels employs a portable oscilloscope (a hand-held Fluke 124B industrial ScopeMeter), a small trench, and a tarp. Once caught, the eels go into paddling pools to reduce the shock of captivation and help them settle down. Crampton then prepares the area for the measurements by digging an eel-sized trench in the ground that will help hold the eel securely in place. The trench is covered with a non-conductive plastic tarpaulin, necessary to isolate the eel and remove it from the load of the water to get an accurate reading. The portable oscilloscope is set up for a differential voltage measurement. To get an electrical reaction out of the eel, Crampton holds one probe tightly on the tail and uses the other probe to prod eeworldonline.com

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PORTABLE SCOPE APPS

Length

Voltage measurement

1.30 m

703 V

1.35 m

710 V

Eel measurement data using a Fluke 124B Industrial Portable Oscilloscope. | Will Crampton

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the eel’s snout. With the meter set to triggered acquisition, the oscilloscope captures short pulses of electricity. Once the measurements are taken, Crampton uses the cursor function to measure the difference between the highest and lowest point of the pulses. The new measurement technique developed by Crampton earned him a Guinness World Record for most electric animal; an electric eel measuring in at 860 V took the title. Previously, the highest voltage output measured was also from an electric eel but was closer to 650 V. Crampton used the same measurement method to break the world record as he did on a recent trip to Guyana. Crampton went back to the Amazon to try and break the world record again as part of ﬁlming an episode for a BBC show called Animal Impossible. Crampton and a video crew spent nine days in Guyana looking for and measuring the voltage of electric eels. They recorded measurements from two different electric eels— both were the E. Electricus species—measuring in at 1.30 and 1.35-m long. Voltage readings for both eels were above 700 V, which would have broken the previous record. 6 • 2020

Interest in the electrogenic capacities of electric eels (and their cousins the torpedo/ electric rays) dates back to 1800 when they became models for the first batteries. Understanding more about these animals, including voltage measurements, has helped with medical research leading to amazing discoveries. There are already electric eel organs being used as models for synthetic bio-batteries and future medical applications include powering medical devices like pacemakers or developing “biotechnology to allow human cells to generate sizable electric fields, external electric fields, which could be used as everlasting batteries,” according to Crampton.

REFERENCES Fluke hand-held 124B Industrial ScopeMeter, https:// www.fluke-direct.com/product/ fluke-124b-oscilloscopedual-input-multimeter-andrecorder-with-cursors

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The complexity of wireless receiver tests ERIC HSU | KEYSIGHT TECHNOLOGIES , INC .

The crowded spectrum of today’s RF environment puts a premium on quantifying the performance of radio receivers.

THE DEMAND FOR wireless communications now challenges the physical limitations of today’s wireless communications systems. Interference can easily arise when systems operate in a crowded wireless environment using a shared spectrum. Signal congestion makes the process of designing, testing, and isolating system problems more complex. In the next few years, billions of devices will connect through many different and emerging wireless technologies. Each device may integrate with two or more wireless standards. With many wireless standards using the same unlicensed bands, device manufacturers must verify that neither co-channel nor adjacent-channel interference will degrade their designs. This situation presents challenges to device designers as design and verification testing becomes more complex, time-consuming, and expensive. For example, consider the most commonly used 2.4-GHz industrial, scientific, and medical (ISM) band, which includes wireless standards such as Bluetooth, WI-Fi, and ZigBee. These longtime standards enjoy broad support in both the integrated circuits (ICs) and integrated modules that are built into IoT devices. Co-existence in the unlicensed band comes with a price. Bluetooth uses the frequency-hopping spread spectrum (FHSS) technique, and Wi-Fi uses direct sequence spread spectrum (DSSS) and orthogonal frequencydivision multiplexing (OFDM) as a way to increase resistance to interference. Furthermore, Bluetooth enhanced the FHSS with the adaptive frequency hopping (AFH) to resist interference in the 2.4-GHz ISM band. Wi-Fi added the dynamic frequency selection (DFS) to avoid interference with radar signals in the 5-GHz band. Designers must take various interfering signals into account when evaluating the receiver performance of wireless IoT devices. Consider a digital radio receiver. First, the receiver must extract the RF signal in the presence of potential interference. A preselecting filter, the first component of the receiver, attenuates out-of-band signals received from the antenna. A low-noise amplifier (LNA) then boosts the desired signal level while minimally adding to the noise of the radio signal. Next, a mixer down-converts the RF

A real-time spectrum analysis at the 2.4 GHz ISM band illustrates the crowded spectrum in this band with multiple Bluetooth and Wi-Fi devices simultaneously enabled.

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RECEIVER TESTING Typical digital radio receiver setup Downconverter IF filter

Preselecting filter

Low-noise amplifier (with automatic gain control)

QUANTIFYING RECEIVER PERFORMANCE Several parameters serve to help quantify how receivers behave. The most common measurement parameters include receiver dynamic range,

Output data

A typical digital radio receiver block diagram.

signal to a lower intermediate frequency (IF) by mixing the RF signal with a local oscillator (LO) signal. Finally, the IF filter attenuates the unwanted frequency components that the mixer generates along with signals from adjacent frequency channels. The variations in the receiver’s design manifest after they pass through the IF filter. Receiver design is challenging because the wireless device manages a wide variety of input signal conditions, and they are difficult to predict. Also, you need to inject noise and interfering signals to characterize the receiver’s performance.

signal-to-noise ratios, channel selectivity, blocking, receiver intermodulation distortion, and receiver spurious emissions. A common wireless receiver test is the receiver dynamic range, which includes minimum input sensitivity, maximum input level, and channel noise. For different wireless standards, the definition of the receiver’s dynamic range might be different — it can be the range of input levels or signal-to-noise ratios. A wireless receiver’s dynamic range test is the input power to an RF receiver at a minimum, and maximum level — the bit-error-rate (BER) or packet-error-rate (PER) does not exceed specified values. Wireless standards, such as Bluetooth and Wi-Fi, define wireless receiver minimum input sensitivity and maximum input level test cases. The standards determine the upper and lower levels of the wireless receiver’s dynamic range.

Typical sources of IM

Antenna Pre-selecting filter

Demodulator and decoder

Low-noise amplifier

How intermodulation products may be created in a typical receiver.

IF filter

Mixer

f1 frx1

f2 frx2

frx1 = 2f1 - f2 frx2 = 2f2 - f1 Intermodulation products

Interference signals eeworldonline.com

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6 • 2020

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TEST & MEASUREMENT HANDBOOK IoT wireless connectivity performance standards and characteristics Name

Specification

Modulation

Frequency (MHz)

Bandwidth (MHz)

Range (m)

Bluetooth

Bluetooth SIG

GFSK, D8PSK

2400

ZigBee

IEEE 802.15.4

O-QPSK, BPSK

780, 868, 915, 920, 2450

WiSUN

IEEE 802.15.4g

MR-FSK, MR-OFDM

920

0.2-1.2

1,000

LoRaWAN

LoRa Alliance

GFSK, CCS

169, 433, 470, 868, 915

0.5

10,000

Z-Wave

ITU-T G9959

FSK, GFSK

868, 915, 920

0.2

100

HaLow

802.11ah

OFDM

779, 868, 915, 920

1, 2, 4, 8, 16

1,000

DSRC / WAVE

802.11p

OFDM

5800, 5900

5, 10, 20

1,000

Cat-NB2 (NB-IoT)

3GPP Rel-13

BPSK, QPSK, 16-QAM

GSM / LTE bands

0.18

1,000

Cat-M1

3GPP Rel-13

OFDM

LTE bands

1.4

1,000

C-V2X

3GPP Rel-14, Rel-16

OFDM

Bands 3, 7, 8, 39, 41, 47

2,000

Another definition of dynamic range is a measure of the capability of the wireless receiver to receive a wanted signal in the presence of an interfering signal. This measurement takes place inside the received channel bandwidth in the 3GPP standard (technical specification 36.104, section 7.3). To simulate realistic channel conditions in a repeatable manner, you need to add random noise — additive white Gaussian noise (AWGN) to the wanted signal. Channel selectivity is a measure of the receiver’s ability to receive a wanted signal in the presence of an interference signal with a specified channel offset. The interference can be co-channel, adjacent-channel, or alternate-channel signals. This test verifies that a receiver can establish and hold a connection if other channels are in use. The blocking characteristic is a measure of the receiver’s ability to receive a wanted signal in the presence of an unwanted interferer. The interferer is a modulated or continuous wave interfering signal, typically at a high output power level. The modulated signals simulate co-location with other wireless devices but in a different wireless format. Third- and higher-order mixing of the two interfering RF signals can produce intermodulation signals in the band of the desired channel at a receiver. The intermodulation signals may degrade the receiver’s sensitivity performance. If the interfering signals are f1 and f2, one of the

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third-order intermodulation products (frx1 = 2 f1 – f2 and frx2 = 2 f2 – f1) may fall within the passband of the receiver. Spurious emissions are unwanted emissions that emanate from the devices under test. Receiver spurious emissions are generated internally by the receiver or result from the interaction of the receiver with the coupling transmitter’s signal. A receiver spurious emissions power measures the power of emissions generated or ampliﬁed in a receiver that appears at the antenna connector. The purpose of the test is to limit the interference caused by receiver spurious emissions to other devices or systems.

PERFORMANCE TESTS For long-distance wireless communications, the multipath signals may add up constructively or destructively at the receiver. The Doppler effect causes a frequency shift at the receiver. The effects of multipath and Doppler shift cause linear distortions that are reducible with an adaptive equalizer of a receiver. Also, systems’ channel coding and antenna diversity will reduce the effects. Like the receiver test, test speciﬁcations indicate sensitivity or throughput tests under speciﬁc channel conditions. With multiple wireless standards using the same frequency bands, wireless device manufacturers need to verify not only common receiver test cases but also 6 • 2020

various test scenarios involving interactions of multiple systems. Receiver spurious emissions and intermodulation tests help to identify potential problems with your designs to prevent system degradation. To improve measurement accuracy when you perform these tests, be aware of port termination, signal isolation, and band rejection to improve measurement accuracy. Whether you are working on a single radio format or integrating multiple formats into a wireless device, easy access to the right test signals streamlines validation ensures interoperability.

REFERENCES White paper: Navigate the Complexity of IoT RF Receiver Testing, https://www. keysight.com/us/en/assets/7119-1036/ white-papers/5992-4132.pdf White paper: Making Noise in RF Receivers, https://www.keysight. com/us/en/assets/7018-06389/whitepapers/5992-3446.pdf Application note: Testing and Troubleshooting Digital RF Communications Receiver Designs, https://www.keysight.com/us/en/ assets/7018-06706/applicationnotes/5968-3579.pdf

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OTA TESTING

Verifying 5G with OTA testing ADNAN KHAN | ANRITSU CO.

The 5G realm puts a new emphasis on making measurements without hardwired connections.

5G SYSTEMS are being rolled out globally, bringing with them throughput speeds of up to 10 Gbps, higher frequencies that extend into the millimeter wave (mmWave) spectrum, and devices operating in multiple radio access technologies (RATs). Engineers are faced with considerable design challenges in 5G. Among these challenges is the stringent testing associated with chipsets, devices, and systems. Over-the-air (OTA) testing approaches are becoming the norm for testing 5G New Radio (5G NR) user equipment (UE) and base stations, especially in mmWave. The move to higher frequencies, including sub-6 GHz Frequency Range 1 (FR1) and mmWave Frequency Range 2 (FR2), arises in large part to the crowding of the RF spectrum. For these reasons, 5G NR networks and UE devices require advanced technologies and OTA measurements to characterize performance accurately. For a given transmit power level, mmWave signals do not travel as far as lower-frequency RF/microwave signals. The free space propagation loss is a square function of the frequency and distance. For maximum signal propagation distances, 5G NR systems must direct signal energy between network nodes and UE devices, using active antenna systems (AAS), beamforming, and high-speed signaling techniques. 4G LTE and earlier wireless generations transmitted signal energy in all directions, for a 360° signal around a base station at relatively high transmit power levels compared to 5G NR systems. Operating at mmWave frequencies with lower transmit power levels, 5G networks have considerably more base stations for proper coverage.

ANTENNA ARRAYS Directional signal beams in 5G NR systems are transmitted and received using antenna arrays. Rather than the omnidirectional signal energy transmitted in a 4G LTE system, a 5G NR device will locate a 5G NR base station within range by receiving an identifying signal from the base station. Signaling between the base eeworldonline.com

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station and UE will establish the An example of test equipment for coordinates for directed energy 5G UE device testing that provides beams formed by antenna performance levels exceeding those arrays in the base station and expected of DUTs in terms of frequency device. As such, there can be range, frequency accuracy, signal a communication beam in the sensitivity, and dynamic range. Uplink (UL) and a separate one in the Downlink (DL). A 5G base station is two subsystems – a baseband controller unit and a remote radio head (RRH) – that are connected by a fiber-optic cable. The RRH contains a highly integrated transceiver (TRX) and AAS. 5G NR base stations are smaller and have lower power compared to 4G LTE towers. The size of the antenna is also inversely proportional to the operation frequency. As such, at 28 GHz or 39 GHz, an 8x8 patch antenna array may be 5 cm or smaller. It’s physically not possible to have a connectivity port on the antenna in mmWave. Also, the loss if a cable is connected will be significant. Neither the Base Transceiver Station (BTS) or UE can have a test connectivity port at mmWave. Hence, testing in an OTA environment becomes a necessity for proper RF characterization and performance analysis. Advanced AAS circuits in 5G radio equipment try to maximize propagation distances at mmWave frequencies where signal energy is limited (and more expensive than at lower frequencies). 4G LTE leverages multiple-input, multiple-output (MIMO) antenna approaches to overcome signal path losses and enhance throughput and capacity. 5G NR networks use multiple AAS units in massive MIMO configurations to direct mmWave energy through space as efficiently as possible. 6 • 2020

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TEST & MEASUREMENT HANDBOOK Typical 5G antenna array setup Analog IF

Directional signal beams in 5G NR systems are transmitted and received using antenna arrays. Rather than the omnidirectional signal energy transmitted in a 4G LTE system, a 5G NR device will locate a 5G NR base station within range by receiving an identifying signal from the base station.

Up/down conv

DAC/ADC Base band

Up/down conv Up/down conv

DAC/ADC Up/down conv

An AAS consolidates separate antenna elements, such as an 8×8 array with 64 elements. Each element has controllable amplitude and phase adjustments. Because each element is individually controllable, it becomes increasingly important for testing to calibrate and characterize the antenna array elements so they properly align with frequency and time. This ensures the contributions of the many antenna elements combine to form and “steer” an energy beam in a desired direction

Propagation at the 5G range

4πϝ2Ae c2

ϝ = frequency Ae= Antenna area c = speed of light

For a given transmit power level, mmWave signals do not travel as far as lower-frequency RF/microwave signals. The free space propagation loss is a square function of the frequency and distance.

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precisely. 5G systems have multiple arrays in massive-MIMO configurations for peak use of available signal power at mmWave frequencies. Using advanced signaling techniques, a 5G network node provides a beacon signal for a 5G device in range to identify and synchronize. There are different techniques, such as analog beamforming, digital beamforming, and hybrid beamforming, that are utilized depending on the applications. Significant digital processing is applied in 5G NR signal switching to find the optimum signal path between a base station and a UE to save energy. Signal processing is particularly important at mmWave frequencies where the smaller-wavelength signals suffer reflections from solid objects, such as building walls. There are other losses that the system must be designed to mitigate or handle, such as penetration, reflection, diffraction, foliage, and atmospheric losses. Reflection, free-space loss and diffraction (e.g., the bending of rays around building corners/roofs) loss rises with frequency. Smaller objects, like lamp post surfaces, are more reflective as frequencies rise but seem to make up for loss in diffraction in outdoor environments. Lower frequencies, such as 3.5 GHz, are used for high-coverage lower data rate, while 24 GHz, 28 GHz, and 39 GHz frequencies are allocated for low-latency, smaller coverage, and high-speed data transfers.

MEASUREMENT CHALLENGES Although these advanced antenna techniques make high-speed communications practical for 5G systems at mmWave frequencies, they add complexity to testing. Antennas designed into devices are miniature and tightly integrated with TRx circuitry, making RF probing at points between TRx and antenna circuits impractical.

6 • 2020

Fortunately, by OTA testing in the far field of a 5G UE device’s antenna, a 5G UE device can be fully characterized. A typical OTA measurement environment places the 5G UE device in an EM-shielded chamber to eliminate outside interference. Measurements of the DUT’s antenna radiation pattern take place in the test chamber using an antenna with enough frequency range and performance capabilities. Because measurements of 5G devices take place on antenna arrays, multiple radiation beams are formed close to the individual elements, combining to configure a directed beam further from the array structure. Closer to an antenna (near-field region), the radiation pattern has a spherical shape. Moving further from the antenna (far-field region), the radiation pattern has more of a planar shape. Within the far field is a “quiet zone” where the radiation pattern is most stable and consistent. It is the best location for a test antenna. The distances of near fields and far fields from different antennas and arrays are a function of many variables. Some of the more notable are antenna size, array element size, and spacing between elements, frequency and wavelength. To prevent the test antenna within a shielded enclosure from contributing its own characteristics to the measurement of a DUT’s radiation patterns, OTA measurements are performed in the far fields of both antennas. Ideally, for access to the highest amplitude levels from a DUT, the test antenna is placed as close as possible to the beginning of the DUT’s far field. Choosing an OTA measurement approach involves understanding measurement conditions. A DUT’s far field needs to fit within the test chamber. It must also feature a test setup that can perform

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OTA TESTING Near field and far field R > 0.62 UE

D3 λ

MP A

R> MP B

A visualization of near-field area and far-field area.

2D2 λ MP C

MC D

R : Distance Near field area

Far field area MP : measurement point

measurements with enough range, accuracy, and speed to make 5G UE measurements practical. The most common OTA test approaches are indirect-far-field (IFF), direct-far-field (DFF), and near-field-to-far-field (NFTF) configurations. IFF – Also known as a compact antenna test range (CATR), IFF uses a shaped reflector to collimate beams from a DUT and effectively shorten the distance to the far field. It has less path loss than the longer distance to the far field in a DFF setup. The trade-off is that it can only measure one signal at a time as it has a single feed antenna. IFF typically has a positioner to move the azimuth and elevation of the DUT to create a 3D radiation pattern for testing. DFF – Like IFF, DFF uses a positioner to adjust the DUT azimuth and elevation to create a 3D radiation pattern for testing. Unlike IFF, this chamber can have multiple feed antennas, hence, enabling multiple measurements with different angle of arrivals. This method can result in significant savings in terms of OTA chamber capital cost, as it does not use the reflector. NFTF – With this approach, measurements are first made in the DUT’s near field. Fast-Fourier-transform (FFT) calculations then predict far-field data from the near-field measurements. This is the slowest of the three OTA approaches because of the test and computation times required. OTA testing helps to ensure 5G UE are in compliance with Third Generation Partnership Program (3GPP) standards. Among the critical measurements for 3GPP acceptance are effective isotropic radiated power (EIRP), total radiated power (TRP), effective isotropic sensitivity (EIS), and total isotropic sensitivity (TIS). EIRP determines how much power an omnidirectional antenna needs to transmit in all directions to match the signal strength of a directional antenna in one direction. EIS measures the sensitivity of an antenna to detect signal energy in one direction. EIRP and EIS measurements can provide details on locating the beam peak transmitted by a UE device and its sensitivity to detecting the identifying beam transmitted by a 5G network node, base station, or “hot spot.” OTA measurements require a test chamber based on a designated OTA test method. The reference antenna and test equipment must measure frequency, power, spurious emissions, and error vector magnitude (EVM) of in-phase/quadrature (I/Q) modulated signals in FR1 and FR2 frequency bands to capture higher-order harmonic interference. The proper test setup will

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include a signaling tester that can act as a 5G NR network node (5G nGB) when testing a UE device within the test chamber. OTA measurements on 5G devices pose new test challenges, including evaluating DUTs with multiple RATs, multiple frequency ranges, and advanced AAS architectures. Because of the complexity of beam forming and signal switching in 5G systems, a measurement system must also serve as a 5G nGB. The test solution must provide control of signal frequency and power and evaluate how a 5G UE DUT responds to different signal and beam-switching environments. Because some conformance tests for 5G UE are still in development, the 5G NR test environment is still changing and will benefit from a test solution that can efficiently evolve as standards advance. Test equipment for 5G UE device testing should provide performance levels that exceed those expected of a DUT, in terms of frequency range, frequency accuracy, signal sensitivity, and dynamic range. The measurement uncertainty of the test equipment should be well within the limits of applicable measurement standards and the performance limits of the DUT. Engineers must consider that uncertainty is impacted by the test antenna calibration, DUT positioner, and the frequency accuracy of the test system’s reference oscillator. In a nutshell, the integration of mmWave frequencies, coupled with the exponential increases in bandwidth and latency associated with 5G, have made OTA testing an essential part of the verification process. Selecting the proper test solutions and OTA approaches can improve product design and speed time-to-market.

REFERENCES Anritsu Co., https://www.anritsu.com/en-US

6 • 2020

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TEST & MEASUREMENT HANDBOOK

Work-at-home tools: PC-based instruments address demanding applications TREVOR SMITH | PICO TECHNOLOGY TEST & MEASUREMENT

Advanced technology now lets budgetpriced instrumentation handle tasks once requiring specialized and pricey test gear.

WITH A LARGE SEGMENT of engineers and researchers working at home or away from their lab during the pandemic, there is a large incentive to troubleshoot designs and validate performance using systems that are both precise and that stay within a limited budget. That is one reason why there is growing interest in PC-based systems such as PicoScopes that are able to capture and display complex waveforms that are the heartbeat of nextgeneration electrical and electronic technologies. They address many challenges with mathematical waveform analysis tools, decoding of popular serial communication protocols, and mixed-signal capabilities that span analog/ digital, serial/parallel, high-speed (to 1 GHz) and high-

With dimensions of 245x192x62 mm (9.7x7.6x2.5 in), the 6000E Series oscilloscopes Pico PC-based instruments fit easily on any workbench.

resolution (to 16-bit) technologies. Total cost of ownership of PicoScope PC-based instruments compares favorably with conventional benchtop instruments through free software updates provided throughout the lifetime of the products. Further, an advantage of the PCbased approach is that new PC and display technologies can be swapped in as they become available, upgrading instrument performance. It is useful to review what kind of accuracy this sort of equipment can provide. Pico data loggers enable multichannel recording of scientiﬁc and engineering parameters such as temperature (to 0.015°C accuracy), voltage (to 0.1% accuracy and 24-bit resolution), current, force, strain,

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PC-BASED INSTRUMENTS

Pico data loggers enable multi-channel recording of scientific and engineering parameters such as temperature (to 0.015°C accuracy), voltage (to 0.1% accuracy and 24-bit resolution), current, force, strain, vibration and many others. Alarms can be set to warn or take action on measurements that are out of limits. Annotations can be made during recordings to aid documentation of the results.

vibration and many others. Alarms can be set to warn or take action on measurements that are out of limits. Annotations can be made during recordings to aid documentation of the results. Pico radio frequency (RF) products include a vector network analyzer (VNA) that is invaluable for characterization of high-frequency communications networks and numerous other applications including materials and life sciences research. Pico sampling scopes offer bandwidth to 25 GHz for characterization of high-speed data networks and transmission lines.

Pico Test & Measurement products are PCbased, connecting to and employing industrystandard computer hardware and software for control, display and results analysis. The beneﬁt of this approach is that the instruments are more compact and less costly than traditional benchtop instruments. It also means that users can upgrade their computer at any time to take advantage of processor performance improvements. Pico also provide free-of-charge updates to the application software throughout the lifetime of the instrument. A recent development in this area is

the PicoScope 6000E Series oscilloscope encompassing eight and four-channel models, each of which can be configured with 16 optional digital channels. These products sport bandwidths of 300 or 500 MHz, 8-bit or 8/10/12-bit flexible resolution and up to 4 GS deep capture memory. Pico PC-based instruments fit easily on any workbench and are increasingly being selected by engineers working in a laboratory or at home who need professional test equipment that fits in limited available space and within budget. The PicoScope 6000E Series addresses

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TEST & MEASUREMENT HANDBOOK

The PicoScope 6000E Series, coupled with PicoScope 6 application software, provides advanced debugging tools to accelerate development of high-end embedded systems, signal processing, power electronics, mechatronics, and automotive designs. mainstream test engineering requirements faced by engineers developing next-generation embedded systems. The PicoScope 6000E Series, coupled with PicoScope 6 application software, provides advanced debugging tools to accelerate development of high-end embedded systems, signal processing, power electronics, mechatronics, and automotive designs. The PicoScope 6000E Series incorporates many features as standard, such as 21 serial protocol decoder/analyzers, spectrum analysis capability, a 50-MHz arbitrary waveform generator, and user-deﬁned math and alarm functions for in-depth analysis and long-term unattended testing. With dimensions of 245x192x62 mm (9.7x7.6x2.5 in), the 6000E Series oscilloscopes Pico PC-based instruments ﬁt easily on any workbench. A free software development kit (SDK) available by download enables users to write their own applications around the PicoScope 6000E hardware. The SDK includes instrument drivers for Windows, macOS and Linux, and code examples in C, C#, C++ and Python. Drivers are also provided to interface with widely used third-party software packages such as Microsoft Excel, National Instruments LabVIEW and MathWorks MATLAB. Pico is an approved MathWorks Connections Program

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Partner with extensive in-house MATLAB developer experience. Full capabilities of the PicoScope 6000E hardware are exposed to the programmer via the API, which enables development of custom and OEM applications in scientiﬁc, research, industrial, automotive and power applications.

REFERENCES Pico Technology, https://www.picotech.com/

6 • 2020

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5G TECHNOLOGY WORLD Delivers the Latest 5G Technology Trends

5G Technology World is EEWorldOnline’s newest site covering 5G technology, systems, infrastructure, and wireless design and development. Get caught up on critical 5G information, check out the following articles on 5GTechnologyWorld.com: Massive MIMO performance testing: Emulate the channel Performing MIMO testing using real-world conditions is critical for successful 5G deployments. www.5gtechnologyworld.com/massive-mimoperformance-testing-emulate-the-channel

5G is hot, keep your components and systems cool 5G’s antennas and the devices that drive them generate more heat than their LTE predecessors. That creates new cooling problems for wireless devices and systems. www.5gtechnologyworld.com/5g-is-hot-keep-yourcomponents-and-systems-cool

5G moves into production, causes test issues 5G Technology World talks with Teradyne’s Jeorge Hurtarte, who explains components and over-the-air production test of 5G components. www.5gtechnologyworld.com/5g-moves-intoproduction-causes-test-issues

IEEE 1588 adds timing performance while reducing cost and risk GPS and GNSS have been the standards for network timing, but they have security issues. A Master clock and IEEE 1588 reduces the risk and lowers installation costs. www.5gtechnologyworld.com/ieee-1588-adds-timingperformance-while-reducing-cost-and-risk

For additional content, go to: www.5gtechnologyworld.com

TEST & MEASUREMENT HANDBOOK

FIPS 140-2 security testing for wireless medical devices JAY WHITE | LAIRD CONNECTIVITY

Design engineers should be aware of several testing issues surrounding encryption standards designed to protect data from bad actors.

THE BAD GUYS DON’T CARE about your social security number and credit card numbers as much as you might think. Stolen security numbers are almost literally a dime a dozen on the dark web: You can buy them for less than a dollar apiece. And credit card numbers aren’t much more valuable: They often just fetch $5 a card. If you sold both to a hacker, you would barely have enough to pay for a latte and leave a decent tip for the barista. These price tags might seem surprising, given how much effort people and companies put into trying to keep SS#s and CC#s secret. But clearly that’s not what online criminals are shelling out their ill-begotten dollars and rubles for. But hackers and fraudsters are willing to pay for medical health records. Those are where the action is at on the dark web. Becker’s, the influential healthcare publication, reports those fetch $1,000 on the dark web. It’s no wonder, then, that hackers have their eyes on the IT systems of hospitals, clinics and other healthcare organizations. That includes wirelessly-connected medical devices, which may be viewed as a way to gain access to IT systems and to gain visibility into confidential patient information. To counter this threat, regulators and the healthcare industry have focused on the security of these devices, and FIPS 140-2 is critical to the next wave of security measures. FIPS 140-2 didn’t originate in healthcare. It is a security standard the U.S. government uses for protecting sensitive but unclassified information in IT devices and systems. FIPS stands for Federal Information Processing Standard, and encryption is at the heart of how it protects data both in motion and at rest. Encryption for information that is in transit has been a common element of security protocols for quite some time. Before data is sent from point A to point B, it is encrypted at the beginning of the journey and then decrypted at the other side. This type of encryption even pre-dates the computer age. The Romans used a version of this technique to deliver secret messages to military commanders. The same principles are behind the encryption of data in transit today, but with 256bit encryption rather than an alphabet cipher that Julius Caesar used. The other key kind of encryption is for data at rest, which is about protecting it anywhere it is stored. This is particularly important for wirelesslyconnected devices, used to hold confidential information. Those two types of protection are both vitally important for healthcare, where electronic health records and confidential patient data

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6 • 2020

is not only being sent back and forth between devices and healthcare IT systems, but also residing on medical devices. FIPS 140-2 may not have been designed with healthcare in mind, but it’s become the gold standard for securing patient information and is being rapidly adopted by healthcare companies and device manufacturers. For those wanting a deeper dive into how FIPS 140-2 protects healthcare data, my colleagues recently published a white paper, “Understanding Data Encryption and FIPS 140-2 Within the Healthcare Environment,” that is an excellent resource. It explains how this data encryption is useful for healthcare and provides practical guidance about how it fits into a broader security strategy for healthcare companies. The industry is moving toward broad adoption of this security standard in a way that will make FIPS 140-2 compliance and certification a critical requirement for engineering teams bringing wirelesslyconnected medical devices to market. There are a number of key takeaways from my own team’s experience that can be instructive. We hope this serves as a practical checklist that will help your FIPS 140-2 compliance and certification processes be successful. •

FIPS-Compliant is no longer enough – FIPS certification is complex, so most companies in the industry made the practical choice to have “FIPS-compliant” status as their target. Encryption was implemented through FIPS-validated software such as Open SSL, and that was seen as meeting the necessary threshold for compliance. As the healthcare industry has put a stronger focus on preventing breaches, their expectations about FIPS adoption has shifted as well. Increasingly, the healthcare buyers of medical devices are requiring official FIPS certification. Devices that are only FIPS-compliant are increasingly a deal breaker, which puts the responsibility on design engineers to make device-level certification a mandatory element of their project plans.

•

CMVP is the gatekeeper for being FIPS-certified – To achieve devicelevel FIPS certification, you must successfully navigate CMVP, the Cryptographic Module Validation Program. This is the certification program created jointly by the U.S. and Canadian governments to provide a uniform certification process for manufacturers in both countries. This might be a new acronym for design engineers familiar with agencies regulating wireless products and medical devices, but it’s a critical one. CMVP has accredited independent labs in both countries that specialize in cryptographic and security testing to ensure products meet the standards and can get the FIPS-Certified seal of approval. eeworldonline.com

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SECURITY TESTING General flow of FIPS 140-2 testing and validation Vendor selects a lab; Submits module for testing; Module IUT

NVLAP accredited FIPS 140-2 CMT Lab

Cryptographic module vendor

1 Lab submits questions for guidance and clarification

Test for conformance To FIPS 140-2; Writes test report

NIST / CSE issue testing and Implementation Guidance

1a 4

Issue validation certificate (via lab to the vendor)

Module Coordination

Cost recovery fee received prior to validation

Module's test report

CMT Test report to NIST / CSE for validation; module review pending

NIST / CSE

3 Reviewer assigned module under review

How FIPS 140-2 testing and validation procedures take place for the general case.

•

List of validated FIPS 140-2 modules

All cryptography is not the same – One of the most important things to know about the CMVP testing process is that there is specific criteria for how cryptography is implemented. Engineers who have utilized cryptographic capabilities in the past likely haven’t faced the specificity of CMVP’s standards for encryption, so it’s important to understand what is permitted and what is not. To be approved, sensitive patient data must be encrypted with an approved algorithm. For that reason, the safest route is to choose an FIPS-validated encryption module, which already checks the box for passing this part of the certification process. Know your boundaries – CMVP prescribes encryption technology with

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Finalization; NIST adds module to validated modules list at www.nist.gov/cmvp

FIPS 140-2 security levels Level 1 Examines the cryptographic components of your module’s software. Requires production-grade components but no speciﬁc physical security mechanisms. Level 2 Adds physical security to the software component. Requires physical tamper-resistance (such as tamper-evident coatings or seals or pick-resistant locks) and role-based authentication. Level 3 Adds physical security to the software component. Requires a tamper-proof container to protect the code to prevent intruders from gaining access to the CSPs (critical security parameters) located within the module.

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Level 4 The highest level of security which provides complete protection around the module. Beneﬁcial for modules located in physically unprotected environments or for modules that risk security compromises due to environmental conditions such as temperature ﬂuctuations. Adds physical security to the software component. Requires that the physical security mechanisms are “tamper-active” meaning that the contents of the module are deleted or destroyed if it detects an environmental attack or is physically compromised.

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TEST & MEASUREMENT HANDBOOK no ﬂexibility: Either the crypto module is approved or it will be rejected. But design engineers have more ﬂexibility in setting the boundaries of how encryption is used in their product. There is the option of setting a broad boundary that encompasses the entire device, or you can set the boundary more narrowly to only focus on the cryptographyrelevant components. As an example, one of the key decisions designers will need to think through are the concepts of Data in Motion and Data at Rest and how they relate to your boundary. Data at Rest means the FIPS boundary includes data that is stored on the device (hard drive or similar). Data in Motion means the data-path that is transmitting the data is encrypted using a FIPSvalidated crypto-module. Your team should be thinking as early as possible about the boundary you will present to the CMVPaccredited labs because that will steer the entire testing process later on.

paths in our own FIPS 140-2 design strategy and certification plan. What we found, though, is that the do-it-yourself route is slow, complex and expensive. The lesson here is similar to that from wireless certifications with regulatory agencies like the FCC. Yes, it’s possible to design something from scratch that will get FCC approval, but it usually makes more sense to use a precertified module. Using a FIPS-validated module will similarly streamline the process by checking many of the boxes the CMVP labs will look for. This approach is particularly impactful for the first step in the certification process (step 1 where the certification lab does a design review, boundary review and architecture review), potentially accelerating that phase of the process because the lab will have immediate clarity into and confirmation of the device’s adherence to many FIPs criteria. •

•

Start as early as possible because there are two steps – For early planning, it is important to think about FIPS 140-2. Every engineering team knows that certification is time consuming, but many may not realize how long FIPS certification takes. The process commonly requires 12-14 months – and that’s when things go smoothly. It can take far longer if there are setbacks. The process takes that long because it’s actually two processes: In the first step the certification lab does a design review, boundary review and architecture review. In the second step the lab submits the data to NIST in the U.S. or its Canadian counterpart for review. Engineering teams must build this into their project timelines as well as begin steps in the FIPS process as early as possible to avoid delays in getting products to market.

•

The fastest route may be a validated module – It is possible to tackle these projects using a combination of software packages and other components to buildout all of the elements that will achieve FIPS 140-2 certiﬁcation. Those tools are readily available. My team worked with many of them as we explored various

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Know your level and set your calendar – There are a couple of additional pieces of advice useful for effective FIPS 140-2 planning. First, FIPS 140-2 has four different levels, and picking the correct one is a critical early step in your design project. The white paper mentioned previously has a detailed discussion of the four levels and for which devices each one is relevant. Most devices only need Level 1, the simplest level to achieve. Other devices, however, may require Levels 2, 3 or 4 – each of which are more involved. Not looking closely at the four levels and selecting the wrong one will likely guarantee major setbacks later in the certification process. So be sure to examine the four paths at the beginning of the design process. The other caveat is about the requirement that FIPS certification be renewed every five years. Unlike some other certifications, it does not last for the life of the product. Your organization will need to map out a strategy for scheduling and conducting certification future renewals to ensure products retain their certification and can stay on the market.

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I hope this article serves as a practical road map for your team as you proceed with projects that must achieve FIPS 140-2. Note also that there is a new version of FIPS on the horizon – FIPS 140-3. That said, FIPS 140-2 will be around for quite a while until 140-3 becomes the dominant protocol. Knowing how to successfully implement FIPS 140-2 will be a vital skill for design projects for the foreseeable future. Even small mistakes with FIPS 140-2 can have major consequences in time to market. Doing the right up-front planning and architecting for FIPS 140-2 can help engineers avoid long delays and high costs that would interfere with a successful product development timeline.

REFERENCES Laird Connectivity, https://www.lairdconnect.com/ White paper, Understanding Data Encryption and FIPS 140-2 Within the Healthcare Environment, https://www.lairdconnect.com/ resources/white-papers/understandingdata-encryption-and-fips-140-2-withinhealthcare-environment

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5G TESTING

Testing regimes for the new frequencies and features of 5G ROHDE AND SCHWARZ

Measurements taking place in pre-commercial 5G network trials provide new insights and overcome uncertainties before the technology’s formal launch.

How 5G is evolving

THE 3RD GENERATION Partnership Project (3GPP) deﬁned ﬁfthgeneration (5G) cellular technology in Release 15, which updated mission-critical (MC) communications and MC service functions, to meet the International Telecommunication Union’s IMT-2020 performance requirements. IMT-2020

• • • • •

NR SBA NG-RAN and NGC Networking slicing EDge computing

• • • • •

IAB NR-U eV2X URLLC and IIoT SEAL

• • •

NTN Frequency bands NR light

Release 17

laid out the basic requirements for 5G

Release 16

networks, devices and services. Release 15 also enabled a variety of services associated with usage scenarios such as enhanced mobile broadband (eMBB), ultra-reliable low-

December 2021

Release 15 June 2020 (5G Phase 2)

latency communications (URLLC), and massive machine type communications (mMTC). Some of the 5G performance requirements spelled out are a 20 Gbps peak data rate, 1 msec radio network latency, 10 Mbps/m2 area throughput, and 1 million (low-rate) IoT devices per square kilometer. Key building blocks for 5G are the New Radio (NR) air interface, new radio and core network architectures, virtualization and automation technologies, and new types of devices. These building blocks enable 5G to offer targeted 5G services. Operators worldwide continue to evaluate pre-commercial network trials to ensure a smooth 5G NR network roll-out. The aim is to overcome the challenge of a more demanding and complex air interface and deliver the commercial and technical beneﬁts offered by 5G. While Release 15 eeworldonline.com

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The evolutionary path of 5G.

2018 (5G Phase 1) provides a solid framework for enhanced network performance and mass offering of amazing services, 3GPP is actively working on further enhancing the framework.

RELEASE 15 3GPP deﬁned the initial ideas for 5G, called 5G Phase 1, in Release 15 (R15). Example features of R15 include the New Radio (NR) air interface, new radio network architecture called next- generation radio access network (NGRAN), new core network architecture called next generation core (NGC) or 5G core (5GC), service based architecture (SBA), network slicing and edge computing. 6 • 2020

3GPP also deﬁned the next phase of 5G, also called 5G Phase 2, in Release 16. Planned features for Release 16 (R16) include NR unlicensed (NR-U), basically a way for devices to share unlicensed spectra by incorporating some kind of coordination mechanism; integrated access and backhaul (IAB), basically an alternative to ﬁber backhaul that extends NR to support wireless backhaul; enhanced vehicle-to-everything (eV2X), UltraReliable Low-Latency Communication (URLLC) features that provide low latency and ultra-high reliability for mission critical applications such as industrial internet, smart grids, and remote surgery; and industrial IoT (IIoT) enhancements DESIGN WORLD — EE NETWORK

TEST & MEASUREMENT HANDBOOK 5G apps waiting to happen and a service enabler architecture layer (SEAL), basically a way for common services to be used across different vertical industries. There is also a Release 17. Potential Release 17 (R17) features include non-terrestrial networks (NTN) (i.e. those using satellites), new frequency bands (e.g. 7 GHz to 24 GHz and > 53 GHz), as well as enhancements to NR sidelink (direct communication between devices without going through a base station) and NR light, basically NR extended to simple devices such as low-end wearables or industrial sensor networks. Some features may initially be introduced in one release, but defined in an elaborated fashion in a future release. The 3GPP work in R16 and R17 is classified into the following categories: (i) service expansions, (ii) NR enhancements, (iii) network architecture enhancements and (iv) miscellaneous enhancements. Like LTE, NR uses orthogonal frequency division multiplexing but makes it highly flexible. For example, it introduces variable subcarrier spacing, flexible radio frame structure including a self-contained slot, and carrier bandwidth parts. Both sub-7-GHz spectrum (called frequency range 1 or FR1) and millimeter wave spectrum (called frequency range 2 or FR2) are supported. The new high-performance channel coding techniques of low-density parity check coding (a type of linear error-correcting code) and polar coding (a linear block error correcting code) are defined. Spatial multiplexing techniques used in LTE, SU-MIMO and MU-MIMO (single and multi-user MIMO), are enhanced in 5G. NR is a beamformed air interface with fewer beams at low-frequency bands and more beams at high frequency bands. 5G supports hybrid beamforming where both digital beamforming (available in LTE) and analog beamforming are combined. Massive MIMO in 5G enables enhanced combining of beamforming methods with spatial multiplexing. While NR provides a flexible air interface, it is advantageous in transitioning from 4G to 5G to use dynamic spectrum sharing (DSS) to dynamically allocate 4G and 5G subcarriers in the same channel. Basically, DSS dynamically allocates spectrum resources between 4G LTE and 5G NR based on user demand. With DSS, mobile operators can simultaneously support 4G LTE, 5G NSA and 5G SA devices. DSS was introduced in R15, further refined in R16 and R17 and will probably continue to be refined in future releases, especially to improve the scheduling of resources between and within 4G and 5G subcarriers and across multiple cells. While the transition from one wireless generation to another in a specific band has been a painful experience in the past, it will be much easier with 5G thanks to DSS.

NG-RAN, NGC AND SBA NG-RAN (next-generation radio access network) includes NR-based 5G base stations called next generation node Bs or gNBs. A gNB can be decomposed or disaggregated into a central unit and a distributed unit. Such a gNB architecture reduces infrastructure and transport costs and provides scalability. While LTE uses a limited number of nodes in the evolved packet core (EPC), 5G deﬁnes more network functions (NF) that have fewer responsibilities. The overall 5G system is based on SBA (service-based architecture), where NFs communicate with each other using service-based interfaces. SBA facilitates the

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Satellite access 5G LAN

Haptic services

Critical medical apps

Verticals for positioning use cases

V2X

UAV

Positioning Cyber-physical control apps

Audio-visual production

The applications envisioned for new 5G infrastructure.

design and deployment of the 5G system using virtualization and automation technologies such as network functions virtualization (NFV), software defined networking (SDN), OpenStack (a cloud operating system that manages and controls resources through APIs with common authentication mechanisms) and Orchestration. R15 fully defines two deployment options for the network architecture: non-standalone (NSA) NR and standalone (SA) NR. Non-standalone NR with the EPC (Evolved Packet Core) uses the LTE eNB (Evolved Node B) as the master node and makes use of a gNB’s additional NR radio resources when possible. Standalone NR with the NGC does not rely on the LTE eNB at all and allows direct communications between the UE and the gNB. 3GPP introduces the concept of network slicing, where different logical networks are created using the same physical network to cater to different services and different customer requirements for a given service. Three standard slices for eMBB (Enhanced mobile broadband, an extension of services first enabled by 4G LTE networks that allows for a high data rate across a wide coverage area), URLLC (Ultra-reliable lowlatency communication) and massive IoT are defined with support for numerous operator defined network slices. 3GPP supports edge computing where the applications reside close to the UE. More specifically, 3GPP allows the selection of a gateway that is close to the gNB. Because user traffic passes through a local gateway instead of a remote gateway located deep inside the core network, both the end-to-end latency and transport requirements are reduced.

5G NR TESTING AND DATA ANALYTICS Networks are growing more complex with the emergence of new cellular use cases and more demanding subscriber and machine quality of experience (QoE), enabled by the roll out of technologies such as 5G and internet of things (IoT). Therefore, it becomes more critical to eeworldonline.com

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5G TESTING

understand the current network situation and pinpoint areas for development that will efﬁciently deliver the required performance. Delivering excellent QoS (quality of service) to end users is a primary objective for mobile network operators to retain subscribers, attract new customers and competitively position themselves. A 5G NR measurement solution should provide accurate and reliable data collection with coverage measurements, application QoE measurements, and veriﬁcation of the device interaction with a real 5G NR network. The data analytics of this solution should comprise the entire network testing lifecycle, from network engineering and optimization to benchmarking and monitoring, and have the following objectives: • • •

To effectively store, process and visualize big data To gain deep network insights To ultimately build intelligence for investment prioritization based on the most critical factors inﬂuencing network performance and QoE

To measure and analyze pre-commercial 5G NR trials and early deployments, a real-time analysis tool, such as R&S ROMES4 from Rohde & Schwarz, is sufficient. Network measurements in commercial 5G NR networks require a sophisticated post-processing tool for data analytics. For accurate network engineering, benchmarking, monitoring and optimization, it is necessary to process a large quantity of complex data and produce clear, easyto-understand intelligence in a network to make better decisions. Correct decisions can only be made when they are based on reliable and accurate data, processed quickly and appropriately. By processing data acquired from the end-user perspective, the Rohde & Schwarz data analytics tool SmartAnalytics provides a precise and clear assessment of an operator’s own network quality (QoE from the end-user perspective) and its competitive position in the market. Analytical tools must provide visibility of the main factors influencing network performance and QoE status, its context, development trends, problems and possible degradation causes. Thanks to the network performance score integrated in SmartAnalytics, a software suite that analyzes and post-processes measurement files collected with R&S Mobile Network Testing solutions, network operators can identify strategic areas for investment. As a result, mobile operators can efficiently deliver optimal end-user QoE. SmartAnalytics is a flexible tool that encompasses different mobile network testing use cases such as engineering, optimization, monitoring and benchmarking, using the same user interface and platform. It eliminates eeworldonline.com

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the need for separate test platforms, removes compatibility issues and provides a seamless interface across each stage of the network testing lifecycle. This provides capital and operating expenditure efficiencies in test resources, equipment and execution. In a nutshell, the mobile communications industry undertook a paradigm shift in defining the next generation of mobile communications. 5G Phase 1, or R15, provides a strong foundation for enhancements in future releases by defining a high-performance NR air interface and flexible network architecture. R16 and later releases focus on new verticals to significantly expand the applications of wireless communications. The introduction of new frequencies and features, such as 3.7 GHz and beamforming respectively, make testing particularly important and challenging, despite numerous simulations executed by industry players. Conducting measurements in pre-commercial network trials is the only way to gain new insights and to overcome doubts and uncertainties before the technology’s launch.

REFERENCES Rohde&Schwarz, https://www.rohde-schwarz.com/us/ products/test-and-measurement/overview/ test-measurement_229579.html

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TEST & MEASUREMENT HANDBOOK

Detecting counterfeit integrated circuits without a microscope Curve-trace testing can reveal whether an incoming batch of ICs are bogus without resorting to destructive inspection measures.

MAKING FAKE “lookalike” integrated circuits which resemble real ones takes minimal skill. It may simply require finding cheap parts in the same package and applying new markings. This problem has arisen due to the high value of electronics parts, and the whole manufacturing chain from assembly house to end-user is vulnerable. There are several methods the counterfeiters use to produce their fake goods. Consider just one means, salvaging ICs from old circuit boards. ICs recycled from old PCBs are often so old that they contain lead or other materials now banned by RoHS. Moreover, those built to use tin-lead solder were built to use relatively low peak solder reflow temperatures (typically below 235°C). Today’s lead-free IC packages now see peak reflow temperatures as high as 260°C. Manufacturers that mount what they believe are lead-free ICs

ALAN LOWNE | SAELIG

can unknowingly induce major reliability hazards such as cracking or delamination of the package. Conversely, counterfeiters may mark lead-free packages as leadbearing to meet demands for legacy lead-bearing packages. This may cause tin whiskers to form between adjacent pins and solder balls on ICs. To better mimic original parts, counterfeiters now largely mark IC packages with lasers rather than ink. The problem is that counterfeiters usually do not know the depth of bond wires in plastic packages, especially when they have thinned these packages by chemically or mechanically removing the original package markings. So the fake laser-marking process sometimes partially melts bond wires. Bad laser marking can also compromise hermetic packages. In one case, counterfeiters laser-marked iron-based IC lids plated with nickel and gold. The laser fully removed both layers of plating to expose the underlying iron. Prolonged exposure to moisture would corrode away the iron, allowing moisture ingression. Also in attempting to make old components look new, counterfeiters typically can use acids on package pins and solder balls. These acids may be incompatible

SENTRY contains all the hardware required to analyze the electrical characteristics of ICs with up to 256 pins. 256 pins+ devices can also be tested by rotating the device (BGA, QFP) to allow all pins to be learned and compared. SENTRY contains four 48-pin dual-in-line (DIL) zero-insertion-force (ZIF) sockets; these can be used directly for older DIP components but can also be used to accommodate a variety of additional socket adapters available for different package types. The socket adapter can contain multiple IC sockets to allow testing several ICs simultaneously or comparing one IC with another. An expansion connector allows custom socket adapters with up to 256 pins to be attached.

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COUNTERFEIT ICs

Chip package markings can be made to look almost identical to the uncritical observer. Here the second package is fake. An examination of the die it contained revealed an Intel chip rather than the programmable peripheral interface from NEC that was supposed to be present.

with the package materials, and sometimes counterfeiters don’t wash them off completely. Particularly if the counterfeiters cause package delamination with their antics, acid residues can corrode active die circuitry after months or years of use. Some of the same problems can arise when ICs are new but have been rebadged, remarking cheap ICs to look like more expensive versions. Technical measures to detect counterfeits have previously included visual inspection of devices for marking errors – which needs a trained eye for all possible variations in marking. The x-raying of incoming parts is another technique. Non-destructive imaging techniques such as radiography can generate 2D images showing internal chip features, and computational tomography can generate 3D representations from multiple 2D projections. More sophisticated non-destructive techniques include energy disruptive spectroscopy, which involves high-energy x-rays, and terahertz time-domain spectroscopy. There are also destructive methods that destroy the IC. For example, a complex decapsulation system can be used to visually inspect IC die samples. However, all these procedures are expensive and time consuming. They require skilled operators and expensive equipment. Some distributors have advertised screening services for verifying components with a turnaround time of “as little as two days.” That time frame is unacceptable in many cases. eeworldonline.com

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These companies offer techniques such as x-ray, x-ray ﬂuorescence analysis (XRF), decapsulation, heated solvent testing, visual inspection, and solderability testing. These tests result in detailed reports – when all that is often required is an answer to the question, “Is it a good part?” In reality, this approach is only viable for military or large volume production runs. Another approach for detecting counterfeits is to perform a functional test on a sample of the ICs; logic I/O conforming to a truth table is an example. This technique is faster and less expensive than typical destructive and inspection tests. It will detect gross problems, such as a incorrect logical function, or no function at all, but will miss the subtle ‘out of tolerance’ issues – tell-tale signs that a component is counterfeit. With older-technology IC families, different speed variants are available. Conventional testing equipment with this level of speed test capability is extremely expensive. There is a different kind of non-destructive electrical test used to detect counterfeits. Called a curve-trace test, the idea is to apply a voltage and current to pairs of pins on the IC to gauge the V-I behavior. The stimulus signal can be a sine wave, a triangle wave, a ramp, and so forth. The stimulus is applied to all pins on a known-good part, then the resulting responses serve as a template for what to expect from ICs that aren’t counterfeit. This response is directly related to the device characteristic, its internal structure, and its manufacturing processes. 6 • 2020

These types of tests can detect defects such as missing or broken bond wires, cracked die, and damage to hermetically sealed chip packages. Instruments that carry out curve-trace tests of this sort were originally used to check out discrete transistors and diodes. But these ﬁrst curve tracers generally could only test one discrete semiconductor device at a time. Their modern counterparts are designed with multiple channels to simultaneously stimulate all or most of the pins on a modern IC. An example of one such device in this category is the ABI Sentry Counterfeit IC Detector. Sentry is PC-driven and checks the validity of parts in seconds. The product is designed to be used by personnel in a receiving department. The analysis takes place in the background and the operator only sees a simple “Good Device,, “Blank Device,” or “Fail Device” message, with the option to produce a detailed report to send to the supplier. The ABI Sentry is a benchtop device that uses an advanced form of VI testing to determine an IC’s electrical characteristics or signature. The Sentry’s VI Matrix Test exercises every possible pin combination on the IC under investigation. This provides great insight, more than simple systems that are restricted to testing between pins and ground. The Sentry’s Matrix VI Test can reveal differences between devices with different functionality but similar technology. For example, it can detect a relabeled chip with the same input/output pinout. So the Matrix VI DESIGN WORLD — EE NETWORK

TEST & MEASUREMENT HANDBOOK

VI curves used for verifying the identity of an IC. VI testing applies a voltage waveform between two IC pins and measures how the current drawn changes as the applied voltage varies. This response is directly related to the device characteristic, its internal structure and manufacturing processes. These curves were taken using an ABI Sentry.

Test yields much more useful data than the more limited pin-to-ground test. The VI characteristics captured by Sentry are called PinPrints and are the unique signature for a device. In operation, technicians would ﬁrst use Sentry to test a known-good device and obtain its “gold standard” signature. They would then compare subsequent signatures of incoming, unknown chips with the knowngood version to check for discrepancies. Small variations are likely to indicate that the chips are from different manufacturers, or possibly different batches from the same manufacturer. Larger differences, however, suggest that the chips are faulty or counterfeit. Sentry can be customized for each IC type by setting tolerances that deﬁne the point at which a tested device is deemed bad. If no reference devices are available there are two alternatives. Reference data can be imported into the Sentry database from other machines or libraries. Alternatively, and not quite as good, testing can be done across a batch; if there is any variance then the whole batch becomes suspect and should be rejected. A package with no internal die is easily detected - all pins will show the straight line ‘null response’ of an open-circuit. Sentry uses a comparative technique to rapidly analyze and learn new components, and then test the unknown parts. A known-good component is locked into a ZIF socket while a test pattern is applied across all its pins. The component’s response to this test pattern is automatically measured and stored as a benchmark. Sentry uses a combination of electronic parameter settings (voltage, frequency, source resistance and waveform) to generate the “signature” for each pin of the IC it checks. It then compares the unique electrical

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characteristics of known components and with suspect components. The testing between every possible pin combination maximizes the chances of capturing internal fault conditions. Sentry can quickly detect missing or incorrect dies, lack of bond wires, inaccurate pin outs and pin impedance variations. Simple pass or fail results are returned after testing. Controlled via USB using PC software, Sentry’s device library can be built up by adding speciﬁc known good devices. The device database can include documents such as photos of device markings, data sheets, and other documentation to further help in conﬁrming the integrity of a device. In the same vein, Sentry can improve quality assurance programs via detailed reports saved to provide quality control traceability. There are efforts afoot to curb various forms of IC counterfeiting. For example, the IEEE P1735 standard spells out ways to encrypt electronic-design intellectual property in the IC hardware and software so chip designers can protect their IP and prevent nefarious manufacturers from copying the chip design. But vulnerabilities have been uncovered in the standard itself. Indications are that the cat-and-mouse game between counterfeiters and manufacturers will be with us for a long time to come. Thus it’s likely that counterfeit detection measures such as electronic testing and package inspection will be necessary for a long time to come.

REFERENCES ABI Sentry, http://www.saelig.com/ product/TSTEQICT001.htm

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CALL FOR NOMINATIONS:

THE 2020 R&D 100 AWARDS What is the R&D 100 awards program? Established in 1962, the R&D 100 Awards is the only S&T (science and technology) awards competition that recognizes new commercial products, technologies and materials for their technological significance that are available for sale or license. There are six categories in the R&D 100, listed below. There are also four special recognition categories, which follow. A given innovation can be entered in both a regular category and any of the special recognition categories — but please note that a separate entry fee is required for each nomination. Special recognition categories are awarded separately from the 100 winners that comprise the R&D 100. In addition, the judging panel will award finalist designations to selected top nominations. This announcement of finalists is made first, followed by the actual R&D 100 winners several weeks later. This allows all finalists and winners plenty of time to make arrangements to attend the awards banquet and/or conference.

SUBMIT YOUR ENTRY TODAY! Deadline for submissions June 26th, 2020 Late deadline for submissions July 15th, 2020 To be eligible for R&D 100 Awards consideration, your product or service must have been made available to the marketplace between January 1, 2019 and March 31, 2020.

THE R&D 100 AWARD WINNERS WILL BE ANNOUNCED ON OR ABOUT SEPTEMBER 15, 2020

Categories include: Analytical/Test

• IT/Electrical • Mechanical/Materials • Process/Prototyping • Software/Services • Other

Special Recognitions: Corporate Social Responsibility

• Green Tech • Market Disruptor – Products • Market Disruptor – Service

FOR MORE INFORMATION OR TO SUBMIT YOUR ENTRY, GO TO:

WWW.RD100CONFERENCE.COM/SUBMISSIONS-FOR-2020

TEST & MEASUREMENT HANDBOOK

The Eclypse Z7 board looks like an FPGA board but harnesses the open I/O standard called SYZYGY.

Work-at-home instrumentation The rise in social distancing has fostered a need for professionalgrade test instruments that function as well at home as in the lab.

THE EVENTS

that have unfolded

across the world since the beginning of 2020 have turned the global marketplace upside down. Few industries have felt this seismic shift as much as engineering, where companies and their employees have traditionally spent much of their time working in a hands-on capacity with numerous pieces of equipment in curated lab spaces and workbenches. The same is true for those electrical engineering students and professors that are being forced out of their comfort zones as well.

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As engineers and students are reluctantly being asked to move those workspaces to their homes, the question remains: Is this a temporary solution or something that can be permanent? The truth is, innovations in athome labs for engineering, ﬂipped classrooms, and online work capacity in recent years have added the ability to serve more engineers, novice and experienced, without increasing the lab space. Whether or not they are having a consistent experience with their test and measurement equipment remains a separate question altogether. Even before COVID-19 and its resulting fallout, engineering companies and universities were increasingly asked to support more while remaining under budget, tasking engineers, 6 • 2020

DAVID HORN | DIGILENT

and academics to make more out of less. One of the most sought-after resource needs in engineering, besides time, is laboratory space, which happens to be an advantage of Digilent’s portable test and measurement devices. The introduction of portable test and measurement devices has added engineering to the list of jobs that can be done fully or partially remote. Scenes of engineers having to take their turns in a secured laboratory for every measurement are becoming less and less frequent. Engineers are constantly asked to produce more, faster, requiring them to adapt and innovate to minimize their design cycle time, all while still meeting strict design requirements. Devices on the desk that could allow engineers to work from home or remotely eeworldonline.com

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HOME INSTRUMENTATION A platform for home instrumentation

Oscilloscope Waveform Generator

Logic Analyzer

Pattern Generator

Network Analyzer

Impedance Analyzer

Power Supply

Protocol Analyzer

The Analog Discovery 2 provides the basis for a number of general-purpose benchtop instruments.

Data Logger

Spectrum Analyzer Voltmeter Static I/O

just starting to creep into the engineering workplace when COVID-19 hit. These portable test and measurement devices, and what they can offer, will become critical pieces of the puzzle in the coming months of, “What now?” Of course, a USB connected device cannot solve all the problems engineers face right now, but until we can get back into the lab, can it solve a lot of them? And once we’re all back in the ofﬁce, can these devices continue to provide convenience, valuable and accurate measurements when a trip to the lab is just not fast enough? eeworldonline.com

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USB AND VIRTUAL INSTRUMENTS It is useful to explore the difference between a USB-connected instrumentation device and a related approach called a virtual instrument. A virtual instrument consists of a PC equipped with software and hardware such as cards and drivers that together perform the functions of a traditional instrument. Software is the main element of a virtual instrument; traditional instruments are hardware focused. A virtual instrument performs three basic functions of a traditional instrument: acquisition, analysis, and data presentation. 6 • 2020

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The two-channel oscilloscope on the AD2 can measure single-ended signals with industry standard BNC oscilloscope probes or differential signals with MTE cables provided with the device.

Programs made in the instrumentation and control program LabVIEW are called virtual instruments, VIs. VIs consist of two fundamental parts, a front panel and a block diagram. Within the interface of the software, there is a table of utilities or set of pallets that contain all the functions with which modiﬁcations to the VI can be made. While a VI can run on a PC, it differs from the approach used USB-based instruments that connect with PCs and use the PC for computational and display purposes. USBbased instrumentation software can take a variety of forms and doesn’t particularly conform to the front-panel/block-diagram structure used with a VI. However, some

USB-based instruments can work with the VI programs created by LabVIEW. One example is the Analog Discovery 2 (AD2). It contains 12 instruments typically found in an engineering laboratory and provides the ability to write custom tests and analyze data with the power of a computer. Many USB instruments focus on one speciﬁc set of measurements or tests, useful in one scenario but not for the broader range of measurements and tests needed throughout stages of design. The AD2 includes analog and digital instruments in the time and frequency domain. Standard on any engineer’s benchtop is the oscilloscope, which is provided on the AD2, with a useful twist. The two-channel

oscilloscope can measure single-ended signals with industry standard BNC oscilloscope probes or differential signals with MTE cables provided with the device. For tests that require stimulation as well as analysis, AD2 includes a two-channel waveform generator that can provide any number of predeﬁned or custom waveforms for stimulus. The software interface – called WaveForms - also provides a network analyzer with the ability to generate Bode, Nichols, and Nyquist plots, among others, so designs can be analyzed and characterized across a wide sweep of frequencies. Long-term measurements can be taken in the data logger, or in a record mode in the oscilloscope. No benchtop would be

A network analyzer function on the AD2 has the ability to generate Bode, Nichols, and Nyquist plots, among others, for characterizing designs across a wide sweep of frequencies.

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HOME INSTRUMENTATION

An impedance analyzer function on the AD2 can quantify inductive and capacitive circuit elements.

complete without a power supply, so there is also a provided positive and negative supply on the device. For quick measurements there is a simpler voltmeter interface as well. The AD2 also provides more advanced instrumentation. When the need arises to quickly determine the frequency components in a signal,

the spectrum analyzer can display signals in the frequency domain with two available channels. Also recently added is an impedance analyzer. When a design or load needs characterization, the impedance analyzer can quantify the inductive and capacitive elements. Almost no engineer faces a modern design challenge involving only analog signals. While digital signals can be viewed and analyzed in the oscilloscope, the AD2 also provides a logic analyzer to automatically decode data, and a protocol analyzer to communicate with a variety of protocols including SPI, I2C, HDMI, and more. When the logic analyzer and oscilloscope are combined this way, both instruments can work in unison to run a real use case stress test. For example, a designer of consumer electronics might have to test a motor and motor driver under real-world conditions. When compared to a traditional lab bench the AD2 provides all the instruments an engineer might need plus some not available in a typical lab. The AD2 user interface is designed to be familiar to those having experience with traditional benchtop instruments. Additionally, it provides the ability to script or write custom applications. The simple script editor in WaveForms allows the AD2 instruments to run a custom test, or a custom decoder. For example, this facility might be used in generating an image from VGA signals or for comparing analog data to converted digital data as when examining the expected and actual result from a DAC under design. The AD2 works with ordinary Mac, Windows, or Linux-based computers. Consequently, software updates can add features and even new instruments. To solve problems, engineers can talk directly to the developers of the products themselves on the Digilent Forum.

Users of the AD2 can a simple script editor to implement tasks such as running a custom test.

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TEST & MEASUREMENT HANDBOOK

Among the instrument functions available on the AD2 is a logic analyzer that will automatically decode data and a protocol analyzer to communicate with protocols that include SPI, I2C, HDMI, and more.

Taking up about as much desk space as a typical mousepad, the AD2 can be expanded with a variety of adapters and accessories. Another product, Analog Discovery Studio, provides the same functions as AD2 but also contains integrated BNC connectors, a more powerful power supply, and a convenient, bread-boardable interface. For jobs focusing primarily in the world of digital signals, a product called the Digital Discovery provides 32 channels at 800 MS/sec and features like selectable logic levels, slew rates, and more. Finally, a similar approach yields the Eclypse Z7, a high-speed analog I/O designed for developing demanding test systems but which is small enough to be used at home,. Many modern electronic systems--including RF, instrumentation, imaging, and test devices--require high-speed and/or high-precision analog inputs. These subsystems may be characterized by a complex mix of analog, digital, and power-supply circuitry. These design specialties are often difficult to find and can slow down and raise the cost of developing and prototyping cutting-edge systems. The Eclypse platform drastically simplifies the task of adding instrumentation-grade analog I/O to FPGA-based systems, speeding the development and prototyping process. The Eclypse Z7 may look like an FPGA board, but it harnesses the open I/O standard called SYZYGY. This standard for high-performance peripheral connectivity includes low-cost, compact, high-performance connectors, a pin

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count that economizes available FPGA I/O, and low-cost cable options. Its software environment helps connect software languages (C++, etc.) to hardware in a way that allows programming by non-hardware engineers. The 500 MHz data rates of the SYZYGY connectors allow for a concept versatile enough to cover a range of high-speed instrumentation and test applications. Looking forward, we expect demand for more portable and mobile devices to bring a need for higher-precision and higher-speed converters that are also energy efﬁcient. We also expect the rising need for RF communications, test, and software-deﬁned radio (SDR) will push more devices to incorporate high-speed analog circuitry. Semiconductor companies are already pushing the speed and bit-depth or precision of their ADCs and DACs, so the bandwidths needed to communicate with those devices are being pushed as well. FPGAs are a good match to interface with these devices, providing both parallel and high-speed transceiver interfaces and the specialized compute resources often required for in-line signal processing and/or control.

REFERENCES Digilent Inc., https://store.digilentinc.com/

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MONITORING HEART RATE

Monitoring heart-rate variability for better athletic performance Sensors and sophisticated algorithms together deliver check heart-rate variability and other exercise metrics. ALISHER KHOLMATOV, RECEP OZGUN MICROS, SECURITY & SOFTWARE BUSINESS UNIT, MAXIM INTEGRATED

FROM WEEKEND WARRIORS

•

to professional athletes, most people who engage in regular sports activity take note of various factors that inﬂuence their performance. Some meticulously track certain metrics from game to game to assess their progression (or lack thereof). Others are diligent about every aspect of their training and practice regimen. The emergence of

Our relaxation response (the parasympathetic nervous system) is the opposite. This is what turns us toward a rest and recovery mode.

HRV tends to be low when we’re in a fight-or-flight mode and high when we’re more relaxed. High HRV is generally associated with greater cardiovascular fitness. The electrocardiogram test is the gold standard for assessing HRV. However, wearable devices with sophisticated algorithms are now making this data more accessible to more people.

sophisticated wearable devices like smartwatches

ANALYZING HRV FOR HEALTH INSIGHTS

and ﬁtness trackers is bringing to light another

Because HRV provides insights into our ANS, it can be considered as the most important general wellness parameter. In the sports world, there’s a growing body of evidence pointing to the role of HRV in setting optimal training loads to enhance athletic performance. For example, a study of cyclists by university researchers in Spain and South Africa found that HRV-guided training led to better performance results. HRV gives us some clues about potential cardiac conditions. Over time, higher HRV can indicate increased resilience, while lower HRV can point to chronic stress. HRV can be increased by changes in behavior: quitting smoking, losing weight if needed, exercising, and managing stress, for example. HRV analysis techniques that fall into three categories provide useful health insights:

important indicator of athletic performance: heartrate variability (HRV). HRV provides a measure of the time difference between successive heartbeats; the variation is controlled by the autonomic nervous system (ANS). This is the system that regulates our heartbeat, blood pressure, and breathing. Our ANS consists of two main components: •

Our “ﬁght-or-ﬂight mechanism” (the sympathetic nervous system) is our response to external stress factors. This is what makes us energized and ready to face challenges.

Autonomic nervous system in action VAGUS NERVE

REST AUTONOMIC NERVOUS SYSTEM

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STRESS

REST AND RECOVER PARASYMPATHETIC

FIGHT OR FLIGHT SYMPATHETIC

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BARORECEPTORS

LONG TERM: HRV INCREASED RESILIENCE

How the autonomic nervous system regulates heart rate through parasympathetic and sympathetic influences.

LONG TERM: HRV CHRONIC STRESS

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TEST & MEASUREMENT HANDBOOK •

•

Time-domain analysis, like standard deviation and root mean square (RMS), provides powerful differentiators of stressed versus relaxed conditions. Some examples include SDNN (the standard deviation of NN (or R-R) intervals), which provides a measure of changes in heart rate stemming from cycles longer than ﬁve minutes, and NN50, which notes the number of pairs of successive NN intervals that differ by more than 50 msec. Frequency domain analysis shows the ratio of parasympathetic and sympathetic activity. High frequency pertains to the parasympathetic system and the vagus nerve, which controls the parasympathetic nervous system Low frequency pertains to sympathetic activity Very low frequency pertains to the sympathetic nervous system, chemoreceptors, thermoreceptors, and the renin-angiotensin system (i.e., hormones) Non-linear analysis can point to underlying cardiac conditions and includes: Detrended ﬂuctuation analysis (DFA), which looks for self-similar patterns by analyzing the power spectral density (PSD). Peaks in PSD indicate repetitive patterns. Entropy analysis, a measure of randomness over time. Decreased HRV and increased randomness of HR are independently associated with high-risk conditions. Poincaré plot analysis utilizes scatter plots of consecutive pulse interval points. Consecutive pulses that vary by large amounts will have larger scattering around the diagonal. Low HRV will shrink and cluster around the diagonal. Unbalanced HR behaviors such as fast acceleration and slow deceleration will generate asymmetric plots. Large off-diagonals show skipped heartbeats, which usually indicate an arrhythmia problem.

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Role of HRV FITNESS & ENDURANCE

BEAT TO BEAT HR

HRV

STRESS & RECOVERY

CARDIAC HEALTH HRV provides an indicator of potential cardiac conditions. UNDERSTANDING EXERCISE METRICS Let’s now take a look at exercise physiology and associated metrics. According to the American Heart Association, cardiorespiratory fitness is a better indicator of mortality than any other risk factors, including smoking, hypertension, and high cholesterol. The current gold standard to determine cardiorespiratory fitness is the VO2 max test, which tests for the maximum amount of oxygen that one can use during intense exercise. VO2 max is related to peak endurance. The test is generally administered in a medical facility using a treadmill and an oxygen mask. Other important exercise metrics include measurements of HR and recovery and of excess post-exercise oxygen consumption (EPOC). Based on the energy expended during exercise, HR goes up to deliver the oxygen needed for energy production. Max HR is the upper limit. The max HR scale is divided into five zones, based on exercise strength or the exercise goal. The target heart rates are agedependent. Zone 1 is the very low intensity zone (50-60% of max HR). Training at this intensity will boost recovery and get you ready for higher zones. Zone 2 is essential for a runner’s program (60-70% of max HR). Exercising at this zone will improve general endurance. The last three zones, however, are the most interesting: Zone 3 is the aerobic level (70-80% of max HR). This is a comfort zone, where oxygen is readily available, and energy is generated mostly from burning fat. Zone 4 is the anaerobic level (80-90% of max HR). This is out of the comfort zone, where the goal is to hit the maximum oxygen consumption 6 • 2020

(VO2 max) and remain there as long as possible to continuing burning fat post-exercise. Zone 5 (more than 90% of max HR) is not recommended, as this is not at a healthy level and can trigger long-term health effects. Recovery time after exercise depends on the total O2 deﬁcit. EPOC refers to the amount of extra oxygen needed to recover after exercise. This extra oxygen consumption actually burns additional calories after exercise. The recovery itself has a fast and a slow component. During the fast component, the muscles return back to their normal state. During the slow component, the lactic acid that is generated during exercise (as glucose is burned to generate energy) is removed from the muscles. EPOC lasts up to 48 hours depending on duration and intensity of the exercise. Besides the gold-standard VO2 max test, there are other well-deﬁned protocols that can guide exercise. Some are geared toward establishing optimal training processes, while others are for improving the oxygen consumption rate and still others are aimed at increasing post-exercise energy consumption. During the exercise, VO2 increases as the workload increases. However, at some point, despite an increase in workload, an individual will reach his or her VO2 max. VO2 can be improved with training. Crosscountry skiers, runners, and swimmers tend to have the largest VO2 max.

HRV-GUIDED TRAINING According to Market Reports Hub, the smart sports and ﬁtness wearables market is projected eeworldonline.com

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MONITORING HEART RATE

to reach $14.9 billion worldwide by 2021. These are the very devices, the analysts note, that are about delivering meaningful data that can turn into actionable information that helps people improve athletic performance or manage overall personal ﬁtness. Indeed, there are now several wrist-worn and even in-ear devices on the market that measure HRV as well as the exercise metrics previously discussed. While their HR measurement accuracy may not be as precise as measurements collected via an ECG based chest-strap device, they provide an indication of VO2 max as well as of parameters like HRV and EPOC. A variety of HRV-based guided exercise applications is also now available. All of these tools provide guidance to help users optimize daily stress load and recovery, personalize training plans based on the individual’s response to stress, plan for periods of rest between activity, and make adjustments to enhance athletic performance. Wearables rely on these key components to deliver accuracy in measuring HRV: proper optical and industrial design, high signal-tonoise ratio (SNR) optical bio-sensors, and, of course, advanced algorithms. From an optical design perspective, because measurements are based on the interaction of light with skin, it is important to consider factors such as crosstalk suppression, separation distance between the device’s LEDs and the photodiode, and optomechanical integration. As HRV is mainly dependent on small beat-to-beat changes in HR periodicity, the most important input here comes from a reliable HR reporting device. The signal quality of this device, whether based on electrocardiogram (ECG), photophlethysmography (PPG), or an acoustic approach, is a limiting factor on accuracy. Bad HR readings can derail HRV measurements and subsequent VO2 max, recovery, and EPOC estimations. The robustness and high signal-to-noise ratio of ECG and PPG sensors used in the reporting device can alleviate the impacts of optical noise on accuracy. Industrial design must factor in where the HR readings will be captured—even elasticity of the wrist strap is crucial. Let’s now spend more time discussing the algorithms. To support HRV-guided training, the algorithms in these wearables must overcome ﬁve foundational challenges that impact accuracy of optical HR measurements:

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Optical noise. Algorithms with capabilities like ambient light rejection and “picket fence” detect-and-replace can, respectively, reduce the undesirable noise and changes in ambient light conditions that hamper accuracy. Impact of sensor location on the body. Muscle, tendon, bone, and overall arm and wrist movement can generate optical noise that impacts measurements. Another factor is the signal response at different wavelengths. Designing a system that consists of multiple sensors and light sources is key to overcoming these challenges. Also, while HR can be tracked during exercise, the best VO2 and recovery estimates can be made at resting states before and after exercise. From an algorithm standpoint, effective algorithms are designed with the ability to utilize the speciﬁcity of the sensor location on the body and to compensate for any related optical noise as necessary. The effects of skin tone. Biological factors such as the darkness of skin, the presence of body hair, and even the presence of tattoos can make it more challenging to capture HR measurements optically because they impact light absorption and, thus, signal quality. Algorithms that account for poor signal quality are needed. The effects of low perfusion, which is an indication of pulse strength and can also be triggered during measurement by low body temperature at the sensor location. Algorithms that account for poor signal quality are needed to cover these cases. Motion compensation, which includes the “crossover” problem, where pulse rate and motion frequency cross over each other when the subject is in motion, negating one of the measurements. 6 • 2020

Algorithms must be smart enough to differentiate between motion and HR modulation. HRV is an important indicator of health, well-being, and general ﬁtness. In addition to aiding in sports coaching and athletic training, HRV monitoring also has applications in areas including stress maintenance and sleep analysis. Health-monitoring wearables equipped with sensors and sophisticated algorithms that together deliver HRV and other exercise metric insights are enabling us to understand, in real time, how we can adjust our training regimens, optimize performance, and manage our ﬁtness goals.

REFERENCES High HRV and cardiovascular fitness, https://www.health.harvard.edu/blog/ heart-rate-variability-new-way-trackwell-2017112212789 HRV-guided training in cyclists, https://www. trainingpeaks.com/coach-blog/new-studywidens-hrv-evidence-for-more-athletes/ HRV analysis techniques, https://www.ncbi. nlm.nih.gov/pmc/articles/PMC5624990/ Cardiorespiratory fitness, https:// www.ahajournals.org/doi/full/10.1161/ cir.0000000000000461 Market Reports Hub, https://www. prnewswire.com/news-releases/smartsports-and-fitness-wearables-market-to-hit149-billion-by-2021-528461241.html Optical design considerations, https://www. maximintegrated.com/en/design/technicaldocuments/app-notes/6/6768.html ECG and PPG sensors, https://www. maximintegrated.com/en/design/technicaldocuments/app-notes/6/6410.html Challenges that impact accuracy of optical HR measurements, https:// www.edn.com/electronics-blogs/aboutembedded/4440217/Optical-heart-ratemeasurement-s-top-5-challenges

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TEST & MEASUREMENT HANDBOOK

Basic test instrumentation and its role in measurements

DAVID HERRES | CONTRIBUTING EDITOR

It can be helpful to understand the differences between common test gear used for bench-top development tasks.

HERE’S A QUICK REVIEW OF some basic instrumentation common to most engineering work benches.

AMMETER

The ammeter is the basis for many other electrical measuring instruments. Whether you are measuring volts or ohms, essentially inside the instrument you are measuring current. Measurement of current in a circuit is somewhat problematic because all the electrical energy to be measured must pass through the meter, so there is the inconvenience of cutting open and later re-terminating the circuit. Another problem is that conventional ammeters, as incorporated in the ubiquitous multimeter, cannot dissipate heat that is greater than just a few amps. The clamp-on ammeter is a work-around. It solves both problems by measuring the magnetic ﬁeld that surrounds any currentcarrying conductor. The instrument is calibrated to read amps. The user closes the jaws around an insulated currentcarrying conductor. It doesn’t matter whether the conductor is centered within the jaws, and it may pass through at an angle. For low-amp measurements, the conductor may be coiled, multiple turns passing through the jaws in the same direction, and then the total reading divided by the number of turns. A hand-held clamp-on ammeter (trade name Amprobe) can be rated as high as 600 A, making it useful for large three-phase motor Typical clamp-on work. Specialized Hall-effect ammeters. instruments can read dc amps.

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VOLTMETER Unlike the ammeter, which is a series instrument, the voltmeter is placed in parallel across a component, conductor, circuit or power source. The full current does not pass through the instrument, only a small fraction of it. The exact amount depends upon the voltage being measured and the impedance of the voltmeter. The input impedance rating of the instrument is all-important and determines how accurately a given circuit can be measured. A low-impedance meter places a heavy load on the circuit under investigation. Used beyond its rating, or with a high-impedance circuit, the large voltage drop can damage the circuit. A high-impedance voltmeter is (relatively) invisible to the circuit under investigation. Nevertheless, it should not be used at voltages exceeding its rating. CAT ratings, which vary with precisely-deﬁned electrical environments, must be observed. These ratings are generally printed adjacent to the inputs. A low-impedance instrument, such as the solenoid voltmeter (tradename Wiggy) is useful in checking for presence or absence of voltage and the approximate level (120 or 240 V) in residential, commercial and industrial branch

A solenoid voltmeter (tradename Wiggy) useful in checking for presence or absence of voltage and the approximate level (120 or 240 V) in residential, commercial and industrial branch circuits and load centers.

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BASIC INSTRUMENTATION circuits and load centers. The loud buzz for ac and single click for dc means you needn’t keep an eye on the readout, and the distinct vibration is useful in noisy locations. This lowimpedance meter is useful for checking GFCI (ground fault circuit interruption) protection downstream from the device. Placing one probe on the neutral wire (white) and the other on the equipment ground (green or bare) or on the equipment chassis will cause the device to trip out if it is receiving power and working. The instrument is not to be left connected to a power source for long, or it will overheat.

OHMMETER The most common type of ohmmeter for general use is incorporated in the digital multimeter. Analog meters, with moving needles rather than digital readouts, are also available, and they are preferred by some old timers. They have the advantage of being more accurate outdoors in cold weather. A reﬂective surface behind the needle aids in eliminating error by facilitating straight-on alignment. Digital multimeters are far more widely used. Bench-type multimeters incorporate the four-wire (Kelvin) option, which is essential for precise low-resistance measurements. Four separate probes, with alligator clip attachments, plug into four dedicated ports, and they are connected to the resistance under investigation. The four-wire setup substantially reduces the effect of cumulative resistance due to measuring leads, contact resistances and electrical paths within the meter. One pair of leads carries the test current from the meter and the other pair measures the voltage drop across the resistance under investigation. This arrangement excludes the unwanted cumulative resistance.

horizontal X-axis. Fractional units such as milliand micro-volts and seconds automatically appear when appropriate. Through the miracle of triggered sweep, a rapidly oscillating periodic signal can be displayed as a single stable waveform. Two external or internally-generated signals can be displayed in separate channels and in the Math mode they can be added, subtracted, multiplied and divided. Other functions, applicable to single waveforms, include square root, integration, differentiation and logarithmic displays. Besides seeing displays in the time domain, the user by pressing a button can instantly see the Fast Fourier Transform of the same signal, displayed in the Frequency Domain, where amplitude as power is plotted on the Y-axis (linear or logarithmic scale) and frequency on the X-axis. This is used for viewing harmonics and calculating total harmonic distortion. Additionally, in the X-Y mode, Lissajous figures are displayed for one signal triggered by a second signal applied to a second channel. These figures change depending upon the amplitude and frequency relations and phase angles. Early analog oscilloscopes applied the external signal more or less directly to the vertical deflection plates, and an adjustable time base to the horizontal deflection plates. In response, the electron beam wrote the uniform

waveform trace on the phosphor coating on the inside of the glass screen, through which it could be viewed as visible light. Today’s digital instruments achieve the same effect with many more functions and analytic capabilities. The signal from each analog input, after preconditioning including amplification or attenuation as needed, goes to a separate analog to digital converter (ADC) in which sampling occurs. The digital output goes to processor, memory and display. The display is a reliable, user-friendly flat screen with no high-voltage deflection needed. The most common liquid crystal displays (LCDs) now found in these instruments typically have LED backlighting. The mixed-domain oscilloscope (MDO) displays the same signal in split-screen format in time and frequency format. The mixedsignal oscilloscope does the same for two separate signals. This is a great diagnostic tool because it correlates in real time digital glitches with intermittent power-supply or other anomalies.

SPECTRUM ANALYZER The spectrum analyzer resembles its close relative, the oscilloscope, the principal differences being: Model for model, the spectrum analyzer is signiﬁcantly more expensive. The spectrum analyzer generally displays

OSCILLOSCOPE The oscilloscope is by far the most versatile and frequently used (with the possible exception of the multimeter) of our many electrical instruments. It is essentially a voltmeter, although equipped with a current probe it can read amps, and in conjunction with another probe reading volts, it can be conﬁgured to graph power. In its most widely-used mode, the time domain, the oscilloscope displays a graph of amplitude in volts along its vertical Y-axis, plotted against time in seconds along its eeworldonline.com

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A Tektronix MDO3104 oscilloscope, frequently used for general-purpose work.

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TEST & MEASUREMENT HANDBOOK

A Tektronix RSA5000 Real-Time Spectrum Analyzer. waveforms in the frequency domain only, while the oscilloscope displays waveforms in the time domain and the frequency domain. The spectrum analyzer has more features, greater analytic capabilities and potentially higher bandwidth and advanced specifications compared to the oscilloscope. Experienced technicians and engineers often find themselves turning away from the oscilloscope in favor of the spectrum analyzer for the most advanced work. The spectrum analyzer front panel has numerous controls that are less intuitive and self-evident than those of the oscilloscope, but a lot of initial difficulties are resolved by consulting user manuals, available for free download at the manufacturers’ websites. As with the oscilloscope, the immediate challenge is obtaining a meaningful display. For the oscilloscope, the answer is to press Default Setup and Autoset. For the spectrum analyzer, to display a non-sinusoidal signal in the frequency domain and see the full range or harmonics, it is necessary to first display the Frequency/Span drop-down menu. Typical menu items are Center Frequency, Span, Start Frequency and Stop Frequency. (R to Center can be temporarily ignored. It has to do with positioning a reference marker at the center of the screen.) Spectrum analyzers fall into three basic categories, swept-tuned spectrum analyzer, vector signal analyzer and real-time spectrum analyzer. The swept-tuned spectrum analyzer incorporates a superheterodyne receiver, which makes use of a local oscillator to downconvert progressive portions of the signal under investigation to display its frequency spectrum as a function of time. You can watch this sweeping action as it moves across the screen. The only disadvantage in this otherwise

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ingenious arrangement is that during the time required for the sweep to be completed, short duration events are sometimes lost. The vector signal analyzer is a variation of the spectrum analyzer that displays the amplitude and phase of a signal at a single frequency, rather than showing the larger spectral context. The principal application is determining modulation quality in design prototypes, using superheterodyne techniques. The real-time spectrum analyzer samples the entire received RF spectrum in the time domain and uses Fast Fourier Transform algorithms to create overlapping spectra so there are no gaps and no missed short-term events.

CURVE TRACER The curve tracer is a member of the oscilloscope family of measuring instruments. In its CRT or ﬂat screen display, the user sees an I-V graph characterizing (typically) a discrete semiconductor. This display differs from a timedomain or frequency-domain display in that current is plotted against voltage. The curve tracer applies this voltage or current to the device under test, which can be an IC, discrete transistor, motor or solar array, among others. In testing a ﬁeld-effect transistor, for example, test voltage from the curve tracer is applied to one input terminal and the common terminal. This voltage is swept and the amount of current at the output is shown in the instrument’s screen, plotted against the applied voltage. This is the I-V curve. In

testing a bipolar junction transistor, rather than voltage, a stepped current is applied at the input terminals. Two devices under test can be connected simultaneously to the curve tester, and as the user toggles a switch, their separate I-V curves are displayed and can be compared. The test is valuable in evaluating proposed devices for differential ampliﬁers, where close matching is required. The curve tracer is widely used by photovoltaic array designers and technicians to test the performance of a prototype or existing installation where the effect of ambient conditions must be distinguished from design or installation faults. As an example, partial shading of an array reduces maximum power output at various times during the day. The curve tracer facilitates PV array diagnosis. Without re-arranging electrical connections, individual panels can be masked to block light, aiding in efﬁcient troubleshooting.

POWER FACTOR METER The Power factor meter, also known as the Cos Phi Meter, is a type of dynamometer wattmeter. The basic principle is that when the field associated with a moving system comes into juxtaposition with the field associated with a fixed coil, the pointer attached to the moving system, properly calibrated, quantifies the deflecting torque in terms of power factor. A dynamometer-type power factor meter consists of two series-connected fixed coils

A power factor meter.

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BASIC INSTRUMENTATION applications, an external frequency reference is coupled with a GPS-regulated rubidium oscillator. Resolution can be enhanced by oversampling and averaging, particularly when the signal under investigation is subject to jitter.

SIGNAL GENERATOR A Tektronix MCA3000 frequency counter. carrying a specific fraction of the load current. Two nearby identical moving coils mounted 90° apart, deflect the needle. This indicator reads power factor 1 at the center of the dial, 0.7 lag at the left and 0.7 lead at the right. When the supplied power is sinusoidal and the load is purely resistive, with neither inductive nor capacitive components, power factor is 1, which is ideal. A load that has inductive or capacitive components is characterized by a lower power factor, falling between -1 (worst) and 1 (best). Most loads having a power factor other than 1 are inductive, and can be corrected by adding power-factor correction capacitors to the mix. They are usually brought on and off line automatically to correct for intermittent inductive loading. The problem with a power factor less than 1 is that it indicates voltage and current are not in phase, so the average product of the two is less than if they were in phase. A load with a poor (less than 1) power factor generates power that then flows back to the source without performing useful work. To prevent overheating in this case, larger conductors and distribution equipment are required. Moreover, there is excessive drag on the generator. Using a power factor meter, utility workers measure the power factor at industrial facilities, which receive a bill for a power factor penalty in negative territory. Therefore, it is in the interest of plant owners to install power factor correction capacitors as needed.

FREQUENCY COUNTER Reasonably accurate frequency counters are incorporated in highend multimeters such as the Fluke 287 and oscilloscopes such as the Tektronix MDO3000 Series instruments. For laboratory applications, there are the Tektronix MCA3000 Series Frequency Counters, selling for $11,200 to $16,500. This is a true microwave counter, capable of measuring up to 40 GHz. It includes an integrated power meter and two additional timer/ counter channels capable of capturing very small frequency and time changes. Analysis modes include measurement statistics, histograms and trend plots, enabling the user to analyze a very wide range of signals. Frequency resolution is 12 digit/s. PC connectivity is enabled by the included copy of NI LabVIEW SignalExpress software. Frequency counters generally operate by counting the number of events within a speciﬁc time interval. When that gate time has elapsed, the number of events per second is calculated and it is displayed in the digital readout. The counter is then reset to zero. To obtain an accurate reading, the time base must be stable, irrespective of power supply and temperature ﬂuctuations and the effects of aging. Often a quartz crystal oscillator is used. It is located within a sealed temperature-controlled “oven”. For critical eeworldonline.com

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Signal generator is a generic term describing various instruments, all sharing a single rationale, which is that a device under test (DUT) requires a periodic analog or digital signal applied at its input. The input may be swept, stepped or modulated. Controls on the front panel permit the user to vary the signal’s amplitude and frequency in order to evaluate the DUT’s response. Signal generators were used extensively by the ﬁrst generation of TV service technicians in the great post World War II consumer electronics boom. Early tube-type CRT TVs were complex energy hogs that required periodic repair. A common procedure was to inject appropriate signals at various stages starting downstream from the tuner, and methodically probing stage, circuit and component inputs and outputs to isolate the fault. Similar procedures were used for radar and other electronic equipment. Today, the basic signal generator has evolved into a number of related instruments with expanded capabilities, which lend themselves to extensive analytics on the receiving end. Types of signal generators include but are not limited to: Function generators, which produce periodic waveforms, individually selected by the user. (Electronics engineers say “waveform” while mathematicians say “function.” They are essentially the same.) These waveform/functions may include Sine wave, Pulse, Ramp, dc, Noise, Sinx/x, Gaussian, Lorentz, Exponential rise, Exponential decay, Haversine and Cardiac among others. Dropdown menus allow the user to vary over a wide range of frequencies/ periods, amplitudes and offsets. In instruments having two or more output channels, phase relations can be set. Modern digital storage oscilloscopes usually contain internal function generators. Freestanding bench function generators have enhanced capabilities such as sweep, burst, modulation and others. Function generators contain electronic oscillators or, in newer models, digital signal processing circuitry to synthesize waveforms, with a digital-to-analog converter (DAC) to produce the analog output. The arbitrary function generator also contains a library of standard waveforms. Additionally, it allows the user to create simple or highly complex waveforms. They may be constructed by altering existing waveforms, drawing traces on the touch screen and then manipulating them, or typing in numerical parameters. RF signal generators and microwave signal generators are similar, but they operate at higher frequencies. At the lower end, their ranges overlap those of the function generators. Microwave signal generators are capable of generating frequencies as high as 70 GHz over coaxial cable and up to hundreds of gigahertz over waveguide media. Vector signal generator – These instruments generate digitallymodulated radio signals using digital modulation formats such as QAM, QPSK, FSK, BPSK and OFDM. Users may test these communication systems by creating custom waveforms and downloading them into the vector signal generator.

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TEST & MEASUREMENT HANDBOOK

Basics of monitoring vs. testing in current, voltage and power WILL DELSMAN | NK TECHNOLOGIES

Industrial measurements often must take place via specialized transducers sized specifically for the current and voltage swings involved.

OLDER AMMETERS worked great when the current ﬂowed at a steady 50 or 60 Hz. Consider the antique GE model

Dealing with distorted waveforms Pure sine wave

8AK1A1AF. I have one that remains accurate after decades of use and

misuse. The nameplate shows “60 Hertz,” denoting its limited scope of applications. Try to get an accurate reading when there is much distortion to the current sine wave shape or if the frequency is anything

other than 60 hertz and you are in for a frustrating experience. Back in the dark ages, test equipment like this old beast utilized a current transformer design based on a toroid. The metal jaws surrounding the conductor were wrapped with many turns of thin copper wire. The magnetic ﬁeld produced by the ac current caused a voltage to be generated in the wraps, and this small voltage would drive the pointer to display the amount of current present. There was no simple method to detect or measure dc current beyond current shunts. Present-day ammeters are most often now designed to use hall-effect elements rather than toroids and can accurately measure ac or dc current. The output from the hall element is conditioned to produce an output proportional to the RMS current regardless of the amount of distortion or harmonic component in the monitored circuit.

TEST VS . PERMANENT MONITORING Test equipment like handheld ammeters and voltmeters are essential tools, but few have the ability to transmit the readings to a remote location or to store the measurement data for later review. And these abilities are usually necessary for industrial data collection. Usually it is a permanently installed device, known to the trade as a transducer or transmitter, that monitors industrial parameters and produces an output which can be stored at the site or uploaded to a cloud service. These sensors produce an output which is typically connected to and read by a panel meter, HMI, programmable controller, or data acquisition system. Generally, industrial transducers must be installed in a cabinet for protection against the surrounding environment conditions while also providing a degree of safety against electrical shock and arc ﬂash. These transducers are designed to be as compact as possible and have

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Actual VFD waveform

Avg (i2)

Average responding transducers are adequate for the measurement of pure sine waves. But the accurate measurement of distorted waveforms as, for example, from variable-frequency motor drives, requires a true RMS transducer.

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MONITORING VS. TESTING mounting options that include snapping onto a DIN rail or mounting with screws to a panel. The current levels involved in many industrial settings are high enough to make the use of current-sensing resistors impractical or ill advised because of thermal issues. Instead, industrial current-measurement sensors typically use induction or Hall effect devices that entail no direct connection to the circuit. These types of devices must have an aperture or sensing window large enough to allow the monitored conductor to pass through easily, and be approved by a third party test lab to be safe when used with the relatively high current and voltage levels that characterize industrial processes.

CONTINUOUS VOLTAGE MEASUREMENT Use of one-piece current and voltage transducers helps keep the necessary panel space at a minimum. In the not too distant past, the production of a signal representing the line-to-line ac voltage--which could be read

by a device like a chart recorder--required a high-accuracy ratiometric potential transformer (PT) and a separate “tin can” signal conditioner. The lower voltage from the PT (usually 120 Vac) rose and fell with the line voltage, and the signal conditioner converted the PT secondary to dc milliamps or low-voltage dc. The resulting signal from the conditioner would go to the chart recorder. The resulting changes in the line voltage were graphed by colored ink from pens mounted over a revolving paper circle or long strip of paper. Set up took a steady hand for positioning the pens so they just touch the paper, and the chart recorder had to be well isolated from vibration or the lines could be shaky and inaccurate. Today, voltage transducers are quite small, even those designed to measure up to 1,500 V. But potentials exceeding this level still need the PT/conditioner approach. Updated designs require two wires for measuring potential, a lowvoltage power supply, and two wires carrying the output signal to a data acquisition system, essentially an electronic chart recorder. The

measurement data can be read on a display immediately, and the chart can be printed for a permanent physical record. There are no errors from vibration or improper pen installation, and pixels do not run out of ink. In addition, there are fewer components, fewer connections, and less labor to install and calibrate. Current measurements have followed a similar progression. In times past, a current transformer (CT) was installed and its secondary connected to the conditioner. The signal conditioner would mount a short distance from the installation point to keep the burden on the CT secondary at a minimum for better accuracy. A shorting block would be installed between the CT and signal conditioner. In the event the conditioner had to be taken out of service, this extra step allowed the CT secondary to stay closed while the monitored circuit current continued to power its load. The shorting block was necessary because a CT should never be energized if the secondary is open, with no load connected, as doing so is quite dangerous.

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TEST & MEASUREMENT HANDBOOK Current sensor basics PLC Analog input

Centrifugal pump M

or Gear pump

Motor starter

APS power monitor

Charging system

Load

Discharge

Charge

An RMS-responding current sensor will produce a signal directly proportional to the current that an industrial load uses. DC current transducers generally employ Hall effect sensors to detect dc currents and cover ranges from 0–5 to 0–2,000 A, with a variety of outputs available to interface with panel meters, programmable logic controllers or building energy management systems. Such sensors can be used to monitor any dc signal to 600 V and carry the UL logo.

In the same physical space as the ancient CT, a modern one-piece current transducer eliminates the issue of CT-toconditioner distance, as the two pieces are fractions of an inch apart inside the sensor housing. There is no need for a shorting block as it would be highly unlikely that the CT could separate from its printed circuit boards. There are also no dangerous voltages present between the sensor terminals when there is no load connected to the transducer. The presentday approach is extremely simple, uses two leads for power and either the same pair or two other wires to carry the output signal. This approach is much safer and reduces the number of connection points signiﬁcantly. Simplicity can be counted on to improve overall reliability. And of course, it is safer to use test equipment for troubleshooting the data acquisition system than for testing the primary, measured circuit. The sensor outputs are at a much lower voltage, but testing must still take place while the monitored circuit is energized to conﬁrm the accuracy of sensor output. When the transducer output produces a “live zero” as with a 4-20 mA output, the 4 mA can be read with many multi-meters on the low dc current setting by simply disconnecting the transducer output at the load (panel meter, PLC, etc.), and connecting the test leads in series between the output and the load. The sensor output will still read 4 mA if the rest of the connections remain in place, including the power supply to the sensor.

SCALING TEST When troubleshooting a transducer, regardless of what property the transducer will measure, make sure to understand what the output should be for a given amount of the measured property. We will use a current transducer as an example: 1. 2.

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Use an ammeter to see how much current gets delivered to the load. Check the current transducer range to ascertain how much current constitutes the maximum output from the transducer. Calculate the expected sensor output. For example, suppose a

6 • 2020

transducer produces 10 Vdc when current rises to 50 A. Divide the output (10 Vdc) by the range: 10/50 or 1/5. So there is 1 V of output signal for every 5 A used. Thus 25 A will create a 5-Vdc output. Another way to arrive at the correct answer: Take the reading from the hand ammeter and divide it by the range, 25/50 = 0.50. Then use that result to show the transducer output: 10 x 0.5 = 5 Vdc. Half the range value will produce half the output value. Thus if the current measured is 37.50 A, multiply by 0.20 and verify that the transducer output is 7.5 V. The same approach is used when the transducer has the “live-zero” output, but the output signal when there is zero current (or voltage, or whatever you are measuring) must be included in the calculation. This is referred to as signal offset. With any analog signal produced by a transducer or transmitter, the device receiving the output (data acquisition system, panel display, PLC, etc.) must be set up so it understands what the output means. For example, a 4-20 mA transducer signal produces a range of 16 mA (20-4). Since the example above describes a 0-50 range, the relationship is 16/50 or 0.32 mA/A. A load of 37.50 A causes a change in the transducer output of 12 mA (0.32 x 37.50). So, with the signal offset value added, the transducer output should be 12 mA + 4 mA = 16 mA. If the need is for benchtop measurements, there are many choices available for ac or dc circuits, current and voltage. If, on the other hand, the need is to store and analyze these measurements, a more permanently installed transducer set will be the best solution.

REFERENCES NK Technologies, https://www. nktechnologies.com/

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Test and Measurement Handbook 2020

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