2010 Test & Design Guide

TM

2010 EMC Test &

Design Guide technologies Filters .....................................................................46 Lightning, Transients & ESD ..........................55 Shielding...............................................................62 Testing & Test Equipment ................................ 8

industries & applications Design.............................................................46, 74 Military .................................................................... 8 Power .....................................................................74 Telecom .................................................................60

directories 2011 EMC Test Lab Directory.........................20 Consultant Services ..........................................31 Suppliers ...............................................................33

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contents 2010 08

TESTING & TEST EQUIPMENT 1.04m Rod, Antenna Factor and Received Level in MIL-STD 462/461E Compared to MIL-STD 461F Test Set Up ......................8 David a. Weston, EMC Consulting Inc.

Effective EMC Troubleshooting with Handheld Probes.............14 Terry noe, beehive electronics; udom vanich, pacifica International

Managing EMC Performance of a Product as it Ages . ............. 36 gert gremmen, ce test; tim haynes, SELEX S&AS; ralph mcdiarmid; Ed price, cubic defense applications; john woodgate, jm woodgate and associates

USB Interface on Laboratory Surge Generators........................ 42 jeffrey d. lind, COMPLIANCE WEST USA

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SPECIAL FEATURE

PAGE 20

2011 EMC test lab directory More than 300 EMC Test Laboratories, arranged by state, with details of services offered and contact phone numbers, are presented as a quick reference guide to EMC testing services.

EMC DESIGN / Filters Clocking Strategies for EMI Reduction ....................................... 46 sassan tabatabaei, sitime corporation

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emc test & design guide 2010

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contents 2010 55

LIGHTNING, TRANSIENTS & ESD How Smaller Form Factors Exacerbate ESD Risks and How Foil Resistors Can Help............................................................................ 55 Yuval hernik, vishay international inc.

departments Editorial............................. 6 Test Lab Directory..........20 Index of Advertisers......88

60

TELECOM Understanding the Changes to FCC 5GHz Part 15.407 Regulations........................................................................................ 60 David a. Case, cisco systems

62

Shielding Differential Transfer Impedance of Shielded Twisted Pairs..... 62 michel mardiguian, EMC Consultant

74

64

PoWER Quality System Compatibility an Essential Ingredient for Achieving Electromagnetic Compatibility and Power Quality for Lighting Control Systems................................................................................74 philip keebler, kermit phipps, Frank Sharp, EPRI Lighting Laboratory.

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InterferenceTechnology—The EMC Directory & Design Guide, The EMC Symposium Guide, and The EMC Test & Design Guide are distributed annually at no charge to qualified engineers and managers who are engaged in the application, selection, design, test, specification or procurement of electronic components, systems, materials, equipment, facilities or related fabrication services. To be placed on the subscriber list, complete the subscription qualification card or subscribe online at InterferenceTechnology.com.

ITEM Publications endeavors to offer accurate information, but assumes no liability for errors or omissions in its technical articles. Furthermore, the opinions contained herein do not necessarily reflect those of the publisher.

ITEMTM, InterferenceTechnology™—The EMC Directory & Design GuideTM, and Interference Technology.comTM are trademarks of ITEM Publications and may not be used without express permission. ITEM, InterferenceTechnology—The Annual EMC Guide, The EMC Symposium Guide, The EMC Test & Design Guide and InterferenceTechnology.com, are copyrighted publications of ITEM Publications. Contents may not be reproduced in any form without express permission.

4

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emc test & design guide 2010

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from the editor 2010 EMC Test & Design Guide

HOLDING STEADY

A

s the economy gained momentum in late 2009 and early 2010, engineering organizations, like every other business sector, sensed promise that a strong, self-sustaining recovery was kicking in. Yet, as government spending to stimulate the economy trailed off and businesses concentrated on rebuilding their inventories, the growth rated started to slow – a pattern that continued through the summer.

Long-term economic growth rate - trending at about 2.5 percent - is not much better, but several market reports released by industry analyst NanoMarkets this year indicate that there are indeed some bright spots for the EMC community.

EMC materials and components markets had until recently been considered highly mature, with few opportunities for firms that were not well established in this field. However, the dramatic increase in the use of radio frequency emitters in the recent past has given a boost to the industry.

In addition to the most visible drivers for the EMC protection markets such as the rise of WiFi and 3G mobile communications, less obvious opportunities are appearing, including the spread of wireless-based navigation systems and electric and hybrid vehicles in the automotive industry, and EMI/RFI and electromagnetic pulse concerns in military electronics. (Smartphones generated 46% of traffic in May 2010, up from 22% two years ago, and 24% of traffic in the U.S. came over Wifi, according to mobile advertising marketplace AdMob. U.S. handset-based navigation usage rose to 24% in 2010 vs. 19% in 2009).

New business revenue opportunities for conductive coatings are emerging from developments in the display, lighting, solar panel, battery and sensor markets. The makers of conductive coatings also will have the opportunity to capitalize on the growth in e-paper and touch-screen displays and the resurgence of crystalline silicon photovoltaics.

Conductive polymers and nanomaterials are gaining importance in the EMI/ RFI sector and there is a robust market for laminates and tapes, as well as higher value component products.

Finally, increased miniaturization of PCBs and hard drives coupled with ever smaller devices on computer chips will increase the threats of damage and costs caused by static electricity which will, in turn, provide the ESD products and coatings market with growth for years to come.

Thus, even as uncertainty remains pervasive throughout the global economy, EMI engineers can take heart in their industry’s resiliency.

Sarah Long Editor

Publisher Paul Salotto Editor Sarah Long Graphic Designer Ann Schibik Production Coordinator Jacqueline Gentile Business Development Manager Bob Poust Business Development Executives Tim Bretz

Leslie Ringe

Daryl McFadyen

Jan Ward

Administrative Manager Eileen M. Ambler Circulation Manager Irene H. Nugent Product Development Manager Helen S. Flood Administrative Assistant Karen Holder Publisher Emeritus Robert D. Goldblum

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USA 1000 Germantown Pike, F-2 Plymouth Meeting, PA 19462 Phone: (484) 688-0300 Fax: (484) 688-0303 info@interferencetechnology.com www.interferencetechnology.com china, taiwan, hong kong Leadzil Jenny Chen +86-010-65250537 E-mail: service@leadzil.com JAPAN TÜV SÜD Ohtama, Ltd. Miho Toshima +81-44-980-2092 E-mail: m-toshima@tuv-ohtama.co.jp ITEM Publications endeavors to offer accurate information, but assumes no liability for errors or omissions. Information published herein is based on the latest information available at the time of publication.

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President Graham Kilshaw

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ITEM TM, InterferenceTechnology™ and InterferenceTechnology.comTM are trademarks of ITEM Publications and may not be used without express permission. ITEM, InterferenceTechnology and InterferenceTechnology.com are copyrighted publications of ITEM Publications. Contents may not be reproduced in any form without express permission.

Copyright © 2010 • ITEM Publications • ISSN 0190-0943

emc Directory & design guide 2010

testing & test equipment

MIL- S T D 462/461E C o m pa r ed t o MIL- S T D 461F Test S et U p

1.04m Rod, Antenna Factor and Received Level in MIL-STD 462/461E Compared to MIL-STD 461F Test Set Up david A. Weston EMC Consulting Inc. Merrickville, Ontario, Canada

I. Introduction his paper shows that the antenna factor of the receiving rod antenna and the E field incident on it, from a standard source of radiation, both change when the counterpoise of the rod is either isolated from the ground plane on the table (new MIL-STD-461F set up), or connected, as per MIL-STD-461E and earlier.

The antenna factor (AF) in dB is defined as 20 log the incident E field in V/m divided by the received level in volts 20*log(E/V).

Reference 1 and Reference 2 discuss the measured antenna factor (AF) of the 41 inch (1.04m) receiving antenna with buffer. The measurements were made using different sources, such as a vertical transmission line and a second passive 1.04m monopole.

It wa s est abl i shed that both the incident E field and the AF depends on the t ype of source and on the connection of the monopole counterpoise to ground.

M IL-STD-4 62 a nd MIL-STD-461D and E show the counterpoise extended and connected to the table via a bonding strap.

This strap is often a

T

Figure 1. Photo of test set up.

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metal sheet with the same width as the monopole counterpoise, as specified in MIL-STD-461E. One of the two configurations tested and reported in this paper was with a metal sheet bonding strap connecting the antenna counterpoise to a ground plane on the table top. MIL-STD-461F categorically states “For rod antenna measurements, electrical bonding of the counterpoise is prohibited� and this was the second configuration tested. This paper shows that measurements made with the counterpoise bonded versus not bonded results in very different received levels. MIL-STD-461F also modifies the rod antenna height so that the center point of the rod is 1.2m above the floor ground plane.

II. Measurement set up In all measurements the receiving rod antenna cable was loaded with 28 material cores. This provides a high impedance and reduces common mode currents on the antenna cable.

The E field incident on the rod antenna, measured with the rod removed is made using a 10cm long bow tie antenna. This is connected to a low noise differential input buffer amplifier with an input resistance of 2 Megohms and an input capacitance of approximately 3pF. The wiring from bow tie to differential input adds approximately a further 2.2pF of capacitance. The differential input is converted to a single sided signal and applied to a detector with a logarithmic response. The detector allows a very high dynamic range. The output of the detector is connected to an A/D converter the output of which is translated to a digital data stream which is the input of a fiber optic driver. emc Test & design guide 2010

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testing & test equipment

MIL- S T D 462/461E C o m pa r ed t o MIL- S T D 461F Test S et U p

III. Measurements Many commercially available 1.04m rod antennas are not calibrated but rely on a purely theoretical value based on antenna and buffer input capacitances. A test method useful from 0.01 to 5MHz, which simulates far field conditions using a plate antenna is described in Reference 1.

The results using the plate antenna with a commercially available buffered rod antenna correspond well with the manufacturers published data. However when the source of radiation is a vertical transmission line, a second rod antenna or the enclosure in a MIL-STD-461 RE102 test set up the measured AF is very different from the far field and dependent on the source.

We measure both the E field incident on the rod antenna with and without bonding the counterpoise to the table as well as the AF of the rod antenna with and without counterpoise bonded. The most significant data for manufacturers of equipment is the received level with the same input signal level applied to the same source measured with and without bonding the counterpoise to the table. Here we assume that the manufacturer uses the same published far field AF of the rod antenna regardless of the test set up.

Figure 2 shows the AF measured both with and without the counterpoise bonded to the table. As seen in Reference 2 the variation in AF below 20MHz is much greater with the counterpoise not bonded. From 20MHz to 30MHz the AF with the counterpoise not bonded is 6dB higher and this is also seen in the Reference 1 test results. Reference 1 provides the AF calibrated on a free space range and the large variations seen in Figure 2 below 20MHz are missing indicating that these are due to the anechoic chamber.

The E field incident on the rod antenna is higher with the counterpoise bonded at most frequencies and this is shown in Figure 3.

Using the same buffered rod antenna the received level with the monopole counterpoise bonded is up to 18dB higher than with the counterpoise not bonded and this is shown in Figure 4.

Reference 4 describes a traditional (MIL-STD-461E) monopole antenna set up in five different chambers with different types and amounts of absorber. It also describes measurements made with a MIL-STD 461F set up. The source of radiation was either a vertical rod above the table top ground plane or a horizontal rod above the table top ground plane. From Reference 4 these resonances are attributable to “ RF current loops between the counterpoise, ground plane, ground plane to chamber connection point (wall to floor), chamber floor and the capacitive coupling back to the antenna counterpoise causes resonant conditions�. However, in Reference 2 the measurements with the counterpoises uncoupled on a free space range with no underlying ground plane shows exactly the same dip followed by peak in AF with approximately the same magnitude as References 4 and 5.

The power cords to the signal generator and spectrum analyzer in the Reference 2 measurement were the only connection to ground and the transmit rod and receive

Measurement without counterpoise bonded Measurement with counterpoise bonded Figure 2. Measured AF of monopole with and without counterpoise bonded and with a simulated EUT as the source.

The electronics and battery are contained in a 6cm x 6cm x 2.5cm shielded box and the only connection to the box is the non-conductive fiber optic cable. The 10cm bow tie is connected to the box using 13cm long thin wires. Thus the perturbation in the measured E field by the measuring antenna cable and equipment is kept to a minimum. The bow tie is calibrated under a strip line antenna. Reference 1 describes the test set up in more detail.

The source is a 0.44m x 0.38m metal box, representing the Equipment Under Test (EUT). The box is insulated from the ground plane and connected to the center conductor of an N type connector mounted in the table top ground plane.

The front edge of the box is 10cm from the front edge of the table in a typical MIL-STD test set up. A photo of the test set up is shown in Figure 1. The signal is injected between the box and ground plane which simulates an EUT with an RF potential between the enclosure and ground plane. This potential is often the result of common mode currents on cables connected to the EUT. Even with the EUT enclosure bonded to the ground plane via a bonding strap, the RF potential may be developed when sufficient current flows to ground in the strap.

The measurements were made in a damped anechoic chamber to simulate a typical MIL-STDRE102 test. This chamber also contains localized ferrite tiles as well as absorber loads and is described in Reference 3 page 581.

Although well damped above 50MHz the chamber does exhibit resonances below 50MHz. Reference 4 describes the chamber to chamber deviations for five different chambers. These range from one containing the MIL-STD-461F minimum absorber requirements to one containing hybrid absorber in a CISPR 25 compliant chamber.

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emc Test & design guide 2010

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testing & test equipment

MIL- S T D 462/461E C o m pa r ed t o MIL- S T D 461F Test S et U p

Signal Integrity...

Measurements with rod removed and without bonded counterpoise. 10cm bow tie Measurements with rod removed with counterpoise bonded. 10cm bow tie Figure 3. Measured E field incident on the antenna counterpoise with the rod removed.

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rod cables were covered in 28 material ferrite. This means that some other mechanism may at least contribute to the dip and peak.

The measurements described in Reference 4 showed the resonance effects to be greater from 10MHz to 30MHz in the MIL-STD-461E set up compared to MIL-STD-461F whereas our measurements showed the resonances to be greater in the MIL-STD461F set up. Reference 5 describes an analysis of the MIL-STD –461E and MIL-STD-461F using a bare room without absorber. Here the prediction is that the resonant frequencies change but the amplitudes remain the same when comparing MIL-STD 461E to F. The same paper shows the room resonances with only 10cm absorber foam but no resonances from 3MHz to 30MHz with 100cm foam exhibiting only 9.5dB attenuation at 30MHz. Reference 4 shows the received level for a vertically oriented source in a well damped chamber to be from 5 to 8dB higher for MIL-STD-461F and 5-10dB higher for the horizontally oriented source.

Whereas Reference 5 shows the theoretical received level to be 10dB higher for MIL-STD-46E versus MILSTD-461F set up. Also Reference 2 shows the AF to be 21dB higher at 16MHz for the MIL-STD-461F set up i.e. 30dB (with delta in E field from Figure 4 ) – 8dB from Figure 2 = 21dB. This means that the received level may be 21dB lower for the MIL-STD-461F versus MIL_STD-46E test set up. The major difference in the Reference 2 set up was that the measurements were made on a free space range with and without ground planes under a transmitting rod antenna and a receiving rod antenna.

This report shows 18dB higher received level for the MIL-STD-461E set up.

Reference 2 also showed the received level from a vertical wire 10cm above a vertical ground plane was higher in the MIL-STD-461E versus MIL-STD-461F test set up. The vertical test set up simulated cables routed down a 18 inch rack. The vertical test set up simulated cables routed down a 18 inch rack. emc Test & design guide 2010

testing & test equipment

W est o n

IV. Conclusions References 2, 5 and this report (above 20MHz) show the output level from a 1.04m rod antenna to be higher with a MIL-STD-461E test set up than MIL-STD 461F. From this report and , depending on the source of radiation, we see it may be up to 18dB lower in the MIL-STD-461F test.

This is important information for EMI test personnel and manufacturers of equipment as it means that an EUT which fails RE102 from 10kHz (2MHz) to 30MHz in earlier MILSTD-461E (and lower) measurements may now pass using the MIL-STD-461F test set up.

REFERENCES • [1]. D. A. Weston Calibration of the 41 inch (1.04m) receiving monopole. Available on the EMC Consulting web site http://www.emcconsulting.com/docs/1mMono.pdf, Feb 22 2009 • [2]. D. A. Weston. High frequency calibration of the 41 inch (1.04m) receiving monopole with and without connecting counterpoises and with different sources. EMC Europe. Wroclaw Poland Wed. 15/09/2010 • [3]. Electromagnetic Compatibility Principles and Applications: D. A. Weston, Marcel Dekker 2000 • [4]. Improving Monopole Radiated Emission Measurement Accuracy; RF Chamber Influences, Antenna Height and Counterpoise Grounding (CISPR 25 & MIL-STD-461E vs MIL-STD-461F) Craig W Fanning.

Elite Electronic Engineering Inc. © IEEE EMC Symposium on EMC 2009.

• [5]. Analysis of MIL-STD-461E and MILSTD-461F RE102 Test Setup Configurations below 100MHz, D. D. Swanson.

Lockheed Martin ©IEEE Symposium on EMC 2008 David A. Weston is principle EMC Engineer at EMC Consulting Inc., Merrickville, Ontario Canada. A member of IEEE and NARTE, Weston has worked full time in EMC for the last 30 years. He is author of the book “Electromagnetic Compatibility: Principles and Application,s” as well as numerous papers and reports, many of which are available at emcconsult inginc.com. He studied at Croydon Technical College from 1960 to 1965. n

Measurement without counterpoise bonded Measurement with counterpoise bonded Figure 4. Received level from the buffered monopole from the same source with and without the antenna counterpoise bonded to the table ground plane.

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testing & test equipment

E f f e c t i v e EMC Tr o u b l e s h o o t i n g w i t h H a n d h e l d P r o b e s

Effective EMC Troubleshooting with Handheld Probes

Terry Noe Beehive Electronics Sebastopol, CA

Udom Vanich Pacifica International Rohnert Park, CA

Introduction MC testing is an unavoidable part of the development cycle for electronic products. As clock frequencies continue to increase, radiated emissions get harder to control. In an ideal world, the R&D engineer would test the emissions from his product early in the design stage and retest frequently as design changes were made, just ass he tests whether his product meets its other design requirements.

Unfortunately, practical constraints make this difficult. Regulatory requirements dictate that radiated emissions be tested at open sites or in shielded rooms. Most companies don’t have the equipment to do this testing, and subcontract it to outside test houses. Even if a company has its own test facilities, these may be booked well in advance, making testing difficult. Either way, the end result is that EMC testing frequently is not done until late in the project development cycle. As a result, designers do not discover EMC failures until late in the development cycle, when schedule pressures are at their highest.

E

The Test-Tweak Cycle When a product fails EMC testing, the 14

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design engineer brings the product back to the lab and tries to isolate the source of the problem. Using measurements, rules of thumb, and intuition, he makes modifications to the design. These changes might include adding shielding to problem circuits, adding filtering to I/O lines, or other modifications.

The product is then returned to the EMC test site, and the tests are repeated. If the product fails, this cycle is repeated again, as many times as necessary: Each iteration through the loop delays product shipment, costs money, and adds to frustration.

To break this loop, we need to be able to do two things: To make radiated emissions measurements on the bench, and to be able to establish correlation between measurements in the lab and measurements at the test site.

Establishing Lab-Test Site Correlation The lab engineer can measure emissions from his product in the R&D lab using handheld EMC probes. The ideal probes have the following characteristics: • Handheld • Repeatable • Compact • Flexible • Wide frequency response • Sensitive to magnetic or electric fields The probes in the Beehive Electronics 101A EMC probe set have all these characteristics. Unlike homebrew probes, their sensitivity is known and specified. The emc Test & design guide 2010

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In Europe, call ar United Kingdom 441-908-282766 • ar France 33-1-47-91-75-30 • emv GmbH 89-614-1710 • ar Benelux 31-172-423-000 Copyright © 2008 AR. The orange stripe on AR products is Reg. U.S. Pat. & TM. Off.

testing & test equipment

E f f e c t i v e EMC Tr o u b l e s h o o t i n g w i t h H a n d h e l d P r o b e s

"The Test-Tweak Cycle” probe set contains both magnetic- and electric-field probes, with individual probes optimized for different frequency ranges.

Since the probes use push-on SMB connectors, cables won’t kink when twisting the probes to reach tight corners.

With repeatable probes, it is possible to establish correlation between measurements on the lab bench and measurements at the EMC test site.

The lab bench and test site readings will then be related by a simple frequencydependent offset. Although it is difficult to predict this offset in advance, it is easy to calculate it in practice with data from both locations.

An Example of Successful Troubleshooting The following example shows how these principles have been successfully used in practice to solve EMC problems by one of the authors.

The product in question underwent radiated emissions testing to CISPR 11 specifications. After testing in the semianechoic room (Figure 2), the device under test (DUT) failed the specification at a frequency of 100 MHz (Figure 3, 100 MHz peak marked with red arrow).

In the graph of Figure 3, the dashed red line represent the pass-fail limit for testing in this particular semi-anechoic room. The 100 MHz emissions were approximately 22 dB beyond the specification limit. This was an alarming problem. Experience suggests that it is very difficult to improve emissions by over 20 dB without significant design changes.

A problem of this magnitude will usually require several design changes to improve the emissions enough to meet the specification. The typical approach would be to make a number of design changes to improve the emissions. After each change, the DUT would be returned to the semi-anechoic room and radiated emissions testing would be repeated. This process is both time-consuming and expensive. In this case, the project schedule would not allow the weeks that might be required to solve the problem.

For this reason, it was necessary to take a different approach. Rather than

Figure 1. The Test-Tweak Cycle.

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interference technology

emc Test & design guide 2010

If you are developing prototype electrical devices and need to evaluate the EMI performance of your new designs and devices, Agilent’s N6141A/W6141A EMC measurement application for its X-Series signal analyzers can help complete your compliance testing successfully. It is the only pre-compliance test solution that enables you to reduce test margins while ensuring your device meets all regulatory limits.

Reduce test margins with superior measurement accuracy The concept of getting a new product to market on time and within budget is nothing new. Recently, manufacturers have realized that electromagnetic interference (EMI) compliance testing can be a costly bottle neck in the product development process. To help ensure successful EMI compliance testing, pre-compliance testing has become an important addition to the development cycle. The basic premise is to measure the conducted and radiated emissions performance of a product during the development phase to identify problems early and thereby solving them before moving on to the next phase of development.

Conducted and radiated EMI emissions

Many manufacturers use EMI measurement systems to perform conducted and radiated EMI emissions evaluation prior to sending their product to a test facility for full compliance testing. Conducted and radiated emissions testing focuses on unwanted signals that are on the AC mains generated by the equipment under test (EUT).

• Identify low-level signals with excellent sensitivity from X-Series signal analyzers • Ensure more precise signal measurements

Easily identify out-of-limit device emissions • See device emissions typically hidden in the noise floor • Differentiate between ambient and DUT signals using signal list features • Identify intermittent signals using Strip Chart features

Maximize signals and compare against commercial and MIL-STD limits • Meet test requirements with built-in commercial and MIL-STD compliant bandwidths, detectors and presets • Compare measured emissions with pass/fail and delta indicators • Use frequency scan to identify, measure and store results

Pre-compliance testing

The frequency range for conducted commercial measurements is from 9 kHz to 30 MHz, depending upon the regulation. Radiated emissions testing looks for signals broadcast for the EUT through space. The frequency range for these measurements is between 30 MHz and 1 GHz and based upon the regulation, can go up to 6 GHz and higher. These higher test frequencies are based on the highest internal clock frequency of the EUT. This preliminary testing is called pre-compliance testing.

To learn more about EMI testing, request the free application note Making Radiated and Conducted Emissions Measurements at www.agilent.com/find/emc-int

testing & test equipment

E f f e c t i v e EMC Tr o u b l e s h o o t i n g w i t h H a n d h e l d P r o b e s

The source was quickly identified as the DUT’s LAN cable.

Next, the DUT’s cover was then removed and further probing was done inside the box. Using the probe, it was easy to identify the source of the emissions.

The 100 MHz emission was the 5th harmonic of the 20 MHz microprocessor clock in the system. This was coupling into the LAN circuitry and, from there, coupled onto the LAN cable.

With the source of the problem identified, the next step was to use the probe to evaluate the effectiveness of design changes. When ‘sniffing’ for radiated emissions, repeatability will be improved if the probe location is held constant. For this reason, the probe was attached directly to the LAN cable with cable ties (Figure 4).

The probe output was monitored on a spectrum analyzer.

The spectrum analyzer was tuned to a center frequency of 100 MHz, and the level of radiated emissions was read using the spectrum analyzer’s markers. Several changes to the design were made. After each design change, the level of the 100 MHz emission was recorded.

Three changes were identified that made significant improvements in the level of radiated emissions: • Ferrites were added to the transmit and receive lines between the LAN transformer module and the RJ45 connector.

• The LAN transformer was changed to a model with a built-in EMI suppressor.

• The LAN cable that ships with the product was changed to one that had a ferrite core around it. Although this was effective, it raises difficult issues. Even if the product is shipped with the special LAN cable, there’s nothing to prevent the customer from using an ordinary cable in the field.

Benchtop measurements predicted that the first two modifications, taken together, would reduce emissions by the required 22 dB. The third fix, changing the LAN cable, should not be necessary. The DUT was returned to the semianechoic room with the first two changes, and the CISPR 11 test was repeated. The results are shown in Figure 5 (100 MHz peak marked with red arrow).

As can be seen from the graph, emissions at 100 MHz were reduced enough to meet the CISPR 11 specification.

Despite the fact that over 20 dB improvement in 100 MHz emissions was needed, the first test of those improvements

Figure 2. Radiated emissions testing in the semi-anechoic room.

Figure 3. Results of initial testing.

evaluating each design change in the semi-anechoic room, each design change would be evaluated on the benchtop in the R&D lab using a small magnetic field loop probe. The improvement in radiated emissions would be measured for each design change. Only when lab measurements showed that the improvements were sufficient to enable the DUT to pass spec would the DUT be returned to the semi-anechoic room for additional (and hopefully final) testing. If the correlation between benchtop and test site measurements was good enough, only one more pass through the semianechoic room would be necessary.

Back in the lab, the first step was to identify the source of the emissions. A small magnetic field loop probe was used to find the location of the strongest 100 MHz emissions.

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emc Test & design guide 2010

testing & test equipment

Noe

Figure 4. Lab measurement of radiated emissions.

Figure 5 (left). Radiated emissions after design changes. design. He is president of Beehive Electronics, which produces a line of EMC test equipment. He also provides consulting and custom design services in the fields of EMC, RF electronics, and transceiver design. He received a BSEE from Virginia Tech in 1985 and a MSEE from Stanford University in 1989.

Udom Vanich received a bachelor’s degree in Electrical Engineering from San Jose State University and a master’s degree in Electrical Engineering from Colorado State University in 1987. He was co-founder of Pacifica International, LLC from 2003 to 2006. He is currently an RF application engineer for CSR. n

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resulted in success. Because radiated emissions could be measured effectively on the lab bench, the test-tweak cycle had been broken.

Handheld probes are just one solution to EMC troubleshooting.

Get information on the latest news and products on the Testing Channel at www.interferencetechnology.com.

TERRY NOE has worked for 25 years in the fields of EMC, RF, and analog interferencetechnology.com

interference technology

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City

Company Name

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Contact

2011 EMC Test Laboratory Directory

City

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC E FCC RTIFICA PAR TI O FCC T 15 & Ns PAR T 68 18 IM M UN L I G H IT Y TN I N M I L G ST R I -STD KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ ME r RTC /CALIB TER A DO RAT I SHI -160 ON ELD I TEM NG EF PES FECT T IVEN ESS

Common sense tells us that most engineers and designers prefer to use local testing facilities. We have created an easy-to-use directory of labs and their services grouped alphabetically by state and city, so that our readers can identify those labs closest to them. We have endeavored to make this directory as accurate as possible; however, we realize that we have not found every lab or listed every service offered. If you own or work for an EMC test lab and we have missed you or omitted one of your services, please let us know. You can add a listing or update your current listing by logging onto www.interferencetechnology.com and following the easy step-by-step instructions. You can also e-mail your additions, revisions, and suggestions to slong@interferencetechnology.com.

Company Name

Contact

Huntsville

EMC Compliance

(256) 650-0646

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Huntsville

NASA Marshall Space Flight Center

(256) 544-0694

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Huntsville

Redstone Technical Test Center (U.S. Army)

(256) 876-3556

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Huntsville

Wyle Labs

(256) 837-4411

Ft. Huachuca

EPG Blacktail Canyon Test Facility

(520) 533-5819

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Phoenix

Compliance Testing, LLC

(480) 268-9712

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Phoenix

Compliance Testing, LLC, aka Flom Test Lab (480) 926-3100

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Phoenix

Sypris Test & Measurement

(602) 395-5911

Scottsdale

General Dynamics Decision Sys. EMC Lab

(480) 441-5321

Tempe

Lab-Tech, Inc.

(480) 317-0700

Alabama

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Tempe

National Technical Systems

(480) 966-5517

Tucson

RMS EMI Laboratory

(520) 794-5972

Agoura

Compatible Electronics, Inc.

(818) 597-0600

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Anaheim

EMC TEMPEST Engineering

(714) 778-1726

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Brea

CKC Laboratories, Inc.

(714) 993-6112

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Brea

Compatible Electronics, Inc.

(714) 579-0500

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Calabasas

National Technical Systems (NTS)

(800) 270-2516

Chatsworth

CKC Laboratories, Inc.

818-678-4362

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China Lake

NAWCWD EMI Lab

(760) 939-4669

Chino

Robinson’s Enterprise

(909) 591-3648

Costa Mesa

Independent Testing Laboratories, Inc.

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(714) 662-1011

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(310) 537-4235

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El Dorado Hills

(916) 496-1760

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E. Rancho Dominguez Liberty Bel EMC/EMI Services Sanesi Associates

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emc test & design guide 2010

City

& canada

Company Name

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Contact

El Segundo

Wyle Laboratories

(310) 322-1763

Escondido

RF Exposure Lab, LLC

(760) 737-3131

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Fremont

CKC Laboratories, Inc.

(510) 249-1170

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Fremont

Compliance Certification Services

(510) 771-1000

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Fremont

Elliott Laboratories

(408) 245-7800

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Fremont

Elma Electronics, Inc.

(510) 656-3400

Fremont

EMCE Engineering, Inc.

(510) 490-4307

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Fullerton

DNB Engineering, Inc.

(800) 282-1462

Gardena

Parker EMC Engineering

(910) 823-2345

Garden Grove

Semtronics

(714) 799-9810

Gilroy

Scientific Hardware Systems

(408) 848-8868

Irvine

Mitsubishi Digital Electronics America Inc.

(949) 465-6206

Irvine

Northwest EMC

(888) 364-2378

Lake Forest

Compatible Electronics, Inc.

(949) 587-0400

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Lake Forest

Intertek Testing Services

(949) 448-4100

Los Angeles

Field Management Services

(323) 937-1562

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Los Gatos

Pulver Laboratories, Inc.

(408) 399-7000

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Mariposa

CKC Laboratories, Inc.

(209) 966-5240

Menlo Park

Intertek Testing Services

(650) 463-2900

Milpitas

CETECOM, Inc.

(408) 586-6200

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Mountain View

EMT Labs

(650) 965-4000

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Mountain View

EMC Compliance Management Group

(650) 988-0900

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Mountain View

Wyle Labs

(650) 969-5500

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Norco

Wyle Labs

(909) 737-0871

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North Highlands Northrop Grumman ESL

(916) 570-4340

Oakland

ITW Richmond Technology

(510) 655-1263

Orange

G & M Compliance, Inc.

(714) 628-1020

Pico Rivera

Stork Garwood Laboratories, Inc.

(562) 949-2727

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Pleasanton

MiCOM Labs

(925) 462-0304

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Poway

APW Electronic Solutions

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(858) 679-4550

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(949) 454-8295

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Redondo Beach

Northrop Grumman Space Tech. Sector

(310) 812-3162

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Riverside

DNB Engineering, Inc.

(800) 282-1462

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Riverside

Global Testing

(951) 781-4540

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Sacramento

Northrop-Grumman EM Systems Lab

(916) 570-4340

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San Clemente

Stork Garwood Laboratories, Inc.

(949) 361-9189

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Rancho St. Margarita Aegis Labs, Inc.

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CA

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

City

Company Name

Contact

San Diego

Lambda Electronics

(619) 575-4400

San Diego

NEMKO

(858) 755-5525

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San Diego

TÜV SÜD America, Inc.

(858) 678-1400

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Santa Clara

Montrose Compliance Services, Inc.

(408) 247-5715

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San Jose

Arc Technical Resources, Inc.

(408) 263-6486

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San Jose

ATLAS Compliance & Engineering, Inc.

(408) 971-9743

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San Jose

Safety Engineering Laboratory

(408) 544-1890

San Jose

Underwriters Laboratories, Inc.

(408) 754-6500

San Ramon

Electro-Test, Inc.

(925) 485-3400

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Santa Clara

MET Laboratories, Inc.

(408) 748-3583

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Santa Clara

Montrose Compliance Services, Inc.

(408) 247-5715

Santa Clara

Wyle Labs

(408) 764-5500

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Silverado

Compatible Electronics, Inc.

(949) 589-0700

Sunnyvale

Bay Area Compliance Labs.

(408) 732-9162

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Sunnyvale

Elliott Laboratories, Inc.

(408) 245-7800

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Sunnyvale

Sypris Test & Measurement

(408) 720-0006

Sunol

ITC Engineering Services, Inc.

(925) 862-2944

Torrance

Lyncole XIT Grounding

(310) 214-4000

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Trabuco Canyon RFI International

(949) 888-1607

Union City

MET Laboratories, Inc.

(510) 489-6300

Van Nuys

Sypris Test & Measurement

(818) 830-9111

Boulder

Ball Aerospace & Technology Corp.

(303) 939-4618

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Boulder

Percept Technology Labs, Inc.

(303) 444-7480

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Intertek Testing Services

(303) 786-7999

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Colorado Springs INTERTest Systems, Inc.

(719) 522-1402

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Lakewood

Electro Magnetic Applications, Inc.

(303) 980-0070

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Littleton

Sypris Test & Measurement

(303) 798-2243

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Longmont

EMC Integrity, Inc.

(888) 423-6275

Rollinsville

Criterion Technology

(303) 258-0100

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Connecticut East Haddam

Global Certification Laboratories, Ltd.

(860) 873-1451

East Haddam

Turnkey OATS Construction, LLC

(860) 873-8975

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Middletown

Product Safety International

(860) 344-1651

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Milford

Harriman Associates

(203) 878-3135

Newtown

TÜV Rheinland of North America, Inc.

(203) 426-0888

Norwalk

Panashield, Inc.

(203) 866-5888

Stratford

Total Shielding Systems

(203) 377-0394

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District of Columbia Washington

22

American European Services, Inc.

interference technology

(202) 337-3214

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emc test & design guide 2010

City

& canada BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Company Name

Contact

Boca Raton

Advanced Compliance Solutions, Inc.

(561) 961-5585

Boca Raton

Jaro Components

(561) 241-6700

Cocoa Beach

Elite Electronic Engineering Company

(800) ELITE-11

Dade City

Product Safety Engineering, Inc.

(352) 588-2209

Dade City

TÜV SÜD America, Inc.

(352) 588-1033

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Jupiter

East West Technology Corporation

(561) 776-7339

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Lake Mary

Test Equipment Connection

(800) 615-8378

Largo

Walshire Labs, LLC

(727) 530-8637

Melbourne

Rubicom Systems, Division of ACS

(321) 951-1710

Newberry

Timco Engineering, Inc.

(888) 472-2424

Orlando

Sypris Test & Measurement

(800) 839-4959

Orlando

Qualtest, Inc.

(407) 313-4230

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Palm Bay

Harris Corporation EMI/TEMPEST Lab

(321) 727-6209

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Alpharetta

EMC Testing Laboratories, Inc.

(770) 475-8819

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Alpharetta

U.S. Technologies, Inc.

(770) 740-0717

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Buford (Atlanta)

Advanced Compliance Solutions, Inc.

(770) 831-8048

Lawrenceville

Motorola Product Testing Services

(770) 338-3795

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Peachtree

Panasonic Automotive

(770) 515-1443

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Acme Testing Company

(360) 595-2785

Addison

Sypris Test & Measurement

(630) 620-5800

Downers Grove

Elite Electronic Engineering, Inc.

(630) 495-9770

Montgomery

E.F. Electronics Co.

(630) 897-1950

Mundelein

Midwest EMI Associates, Inc.

(847) 918-9886

Northbrook

Underwriters Laboratories, Inc.

(847) 272-8800

Palatine

Trace Laboratories–EMC

(847) 934-5300

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Peoria

EMC Testing Inc., A Caterpillar Company

(309) 578-1213

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Poplar Grove

LF Research EMC Design & Test Facility

(815) 566-5655

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Rockford

Ingenium Testing, LLC

(815) 315-9250

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Romeoville

Radiometrics Midwest Corp.

(815) 293-0772

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Wheeling

D.L.S. Electronic Systems, Inc.

(847) 537-6400

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Woodridge

Zero Ground LLC

(866) ZERO-GND

Crane

Naval Surface Warfare Ctr., Crane Div.

(800) 798-2204

Fort Wayne

Raytheon

(260) 429-4335

Indianapolis

Raytheon Technical Services Co., EMI Lab

(317) 306-8471

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Kokomo

Delphi Delco Electronic Systems

(765) 451-5011

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Indiana

interferencetechnology.com

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Company Name

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Cedar Falls

Wyle Labs

(319) 277-9083

• •

Kimballton

Liberty Labs, Inc.

(712) 773-2199

•

•

Elk Horn

World Cal, Inc.

(712) 764-2197

•

•

Rogers Labs, Inc.

(913) 837-3214

Lexmark International EMC Lab

(606) 232-7650

Lexington

Intertek Testing Services

(859) 226-1000

Lexington

dBi Corporation

(859) 253-1178

City

IA

Iowa • • • •

• • •

• • •

Kansas Louisburg

•

•

•

•

• •

•

Kentucky Lexington

•

•

• • • • •

•

•

•

•

•

• • •

Maryland Annapolis

Northrop Grumman Space & Mission Systems (410) 266-1700

• •

Baltimore

MET Laboratories, Inc.

(410) 354-3300

Beltsville

Antenna Research Associates

(301) 937-8888

Columbia

DRS Advanced Programs

(410) 312-5800

Columbia

PCTest Engineering Lab

(410) 290-6652

Damascus

F-Squared Laboratories

(301) 253-4500

Elkridge

ATEC Industries, Ltd.

(443) 459-5080

Gaithersburg

Washington Laboratories, Ltd.

(301) 216-1500

•

Hunt Valley

Trace Laboratories–East

(410) 584-9099

•

Patuxent River

Naval Air Warfare Ctr., Aircraft Div.

(301) 342-1663

Rockville

P.J. Mondin, P.E. Consultants

(301) 460-5864

Rockville

Spectrum Research & Testing Laboratory, Inc.

(301) 670-2818

Salisbury

Filter Networks

(410) 341-4200

Westminster

Electrical Test Instruments, Inc.

(410) 857-1880

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•

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•

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•

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• •

• •

•

•

•

Massachusetts Billerica

Quest Engineering Solutions

(978) 667-7000

Billerica

Sypris Test & Measurement

(978) 663-2137

•

Boxborough

Intertek Testing Services

(978) 263-2662

• • • • • • • • •

Boxborough

National Technical Systems (NTS)

(978) 266-1001

• • • • • • • • • • • • •

Danvers

TUV SUD America Inc.

(800) TUV-0123

•

Foxboro

N.E. Product Safety Society, Inc.

(508) 543-6599

•

Gloucester

Euroconsult, Inc.

(978) 282-8890

•

•

•

Lexington

Design Automation, Inc.

(781) 862-8998

• • •

• • • •

•

Littleton

Curtis-Straus LLC, subsidiary of Bureau Veritas (978) 486-8880

• •

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emc test & design guide 2010

City

& canada

Company Name

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Littleton

Intertek Testing Services

(978) 486-0432

• • • • •

•

• • •

•

Mansfield

Motorola Test Lab Services Group

(508) 851-8484

• •

Marlboro

IQS, Div. of The Compliance Management Group (508) 460-1400

• • •

•

• •

•

Marlboro

The Compliance Management Group

(508) 281-5985

• • •

•

• •

Milford

Test Site Services, Inc.

(508) 634-3444

• • •

• • • • • •

• • •

Newton

EMC Test Design, LLC

(508) 292-1833

Pittsfield

Lightning Technologies, Inc.

(413) 499-2135

•

Wilmington

Thermo Fisher Scientific

(978) 275-0800

•

•

•

• •

•

• •

•

• •

• • • •

•

•

•

• •

•

•

• •

Woburn

Chomerics, Div. of Parker Hannifin Corp.

(781) 935-4850

• •

• • •

• •

Woburn

NELCO

(781) 933-1940

•

Michigan 7233 ITEMSÜD EMC Half_4c Auburn Retlif Hills TÜV America, Inc.

4/30/09 11:28 AM Page 1

(248) 393-6984

•

Aerospace • Automotive Aviation • Consumer Electronics Homeland Security • Maritime Medical • Military • Rail Retlif has touched many worlds for many years.

We are proud to have supported our clients at the highest levels with full Electromagnetic Interference and Environmental Simulation testing services.

Retlif’s engineering and educational services have added tangible value both technically and cost-effectively for over 30 years. We seamlessly guide your products through complex regulatory structures… domestic, international and military…with expertise that expedites the process. And we’re proud to continually offer the industry’s best lead time scheduling.

Retlif is independent…and proud of it… a field leader for over 30 years.

Put us to the test and see why for yourself.

795 Marconi Avenue, Ronkonkoma, NY 11779 USA Tel: (631) 737-1500 • Fax: (631) 737-1497 www.retlif.com • E-mail: sales@retlif.com Additional locations in New Hampshire, North Carolina, Pennsylvania & Washington D.C.

interferencetechnology.com

interference technology

25

Company Name

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Belleville

Willow Run Test Labs, LLC

(734) 252 9785

•

•

•

•

Burton

Trialon Corporation

(810) 341-7931

•

•

•

•

Detroit

National Technical Systems

(800) 946-2687

•

•

Intertek Testing Services

(800) WORLDLAB •

•

• • • • •

• •

City

MI

Grand Rapids Holland

TÜV SÜD America, Inc.

(616) 546-3902

•

Milford

Jacobs Technology, Inc.

(248) 676-1101

•

• •

•

• •

Novi

Sypris Test & Measurement

(248) 305-5200

•

Novi

Underwriters Laboratories, Inc.

(248) 427-5300

•

• •

•

• • •

• •

Plymouth

TÜV SÜD America, Inc.

(734) 455-4841

•

• • • • •

• •

• • •

•

•

Saginaw

Delphi Steering EMC Lab

(989) 797-0318

•

•

•

Sister Lakes

AHD EMC Lab

(269) 313-2433

•

• • •

•

• •

•

Warren

Detroit Testing Laboratory, Inc.

(586) 754-9000

• •

•

• •

•

•

•

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•

• • •

• •

•

Minnesota Brooklyn Park

Northwest EMC, Inc.

(888) 364-2378

Glencoe

International Certification Services, Inc.

(320) 864-4444

•

•

Maple Grove

TUV Rheinland of North America, Inc.

(763) 315-5012

•

Millville

TÜV SÜD America, Inc.

(507) 798-2483

• •

Minneapolis

Alpha EMC, Inc.

(763) 561-4410

• •

• •

Minneapolis

Environ Laboratories, LLC

(800) 826-3710

•

• • •

• • • • •

• •

• •

Minneapolis

Honeywell

(612) 951-5773

•

New Brighton

TÜV SÜD America, Inc.

(651) 631-2487

•

• • • • •

• •

• • •

•

• •

New Hope

Conductive Containers, Inc.

(763) 537-2090

Oakdale

Intertek Testing Services

(651) 730-1188

• •

Rochester

IBM

(507) 253-6201

•

St. Paul

3M

(651) 778-4577

• •

Taylor Falls

TÜV SÜD America, Inc.

(651) 638-0297

•

• • • • •

• •

• • •

• • • •

Boeing-St. Louis EMC Lab

(314) 233-7798

•

NCEE Labs

(402) 472-5880

•

PolyPhaser Corp.

(775) 782-2511

•

• • • •

• • • •

• •

•

• •

•

•

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•

•

•

•

•

•

• • •

Missouri St. Louis

• •

•

•

• • •

•

Nebraska Lincoln

• • •

Nevada Minden

26

interference technology

•

•

emc test & design guide 2010

& canada

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Retlif Testing Laboratories

(603) 497-4600

Hudson

Core Compliance Testing Services

(603) 889-5545

•

•

•

• •

•

Sandown

Compliance Worldwide, Inc.

(603) 887-3903

•

•

• • • •

•

•

City

Company Name

New Hampshire

Goffstown

• • • • • • • • •

• • • • •

• •

New Jersey Annandale

NU Laboratories, Inc.

(908) 713-9300

•

•

•

•

Bridgeport

Analab, LLC

(800) analab-X

•

•

•

•

Bridgewater

Lichtig EMC Consulting

(908) 541-0213

•

Camden

L-3 Communications East

(856) 338-3000

Clifton

NJ-MET

(973) 546-5393

•

•

Edison

Metex Corporation

(732) 287-0800

•

•

Edison

TESEQ, Inc.

(732) 417-0501

•

Fairfield

SGS U.S. Testing Co., Inc.

(800) 777-8378

•

•

•

• •

Farmingdale

EMC Technologists, A Div. of I2R Corp.

(732) 919-1100

•

•

• • • • •

•

Hillsborough

Advanced Compliance Laboratory, Inc.

(908) 927-9288

•

• •

interferencetechnology.com

• • • •

interference technology

•

27

City

NJ

Company Name

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Contact

Holmdel

Global Products Compliance Laboratory

(732) 332-6000

•

• • •

•

•

Lakehurst

Naval Air Warfare Ctr., Aircraft Div.

(732) 323-2085

• •

•

Lakewood

BAE Systems

(732) 364-0049

• • •

•

• •

• •

•

Lincroft

Don HEIRMAN Consultants

(732) 741-7723

•

•

Piscataway

Telcordia Technologies, Inc.

(800) 521-2673

• • •

•

•

• •

• •

Rutherford

SGS International Certification Services, Inc. (800) 747-9047

•

Sayreville

Sypris Test & Measurement

(732) 721-6116

•

Thorofare

NDI Engineering Company

(856) 848-0033

• •

Tinton Falls

National Technical Systems (NTS)

(732) 936-0800

• • • •

Wayne

Sypris Test & Measurement

(973) 628-1363

• • • • • • • • •

•

• • •

•

•

•

•

• •

•

•

New Mexico Albuquerque

Advanced Testing Services, Inc.

(505) 292-2032

White Sands

USA WSMR, Survivability Directorate

(575) 678-6107

• • •

• •

•

•

•

• •

•

Bohemia

Dayton T. Brown, Inc.

(800) TEST-456

• • • • • • • •

• • •

College Point

Aero Nav Laboratories, Inc.

(718) 939-4422

•

•

•

• •

• •

•

• •

Deer Park

MCG Surge Protection, Inc.

(800) 851-1508

•

Deer Park

Universal Shielding Corp.

(631) 667-7900

•

Groton

Diversified T.E.S.T. Technologies

(607) 898-4218

•

• • •

•

• • •

•

Groton

Source 1 Compliance

(315) 730-5667

•

• • •

•

• • •

•

Johnson City

BAE Systems Controls, Inc.

(607) 770-3771

• •

•

• •

•

Johnstown

Electro-Metrics

(518) 762-2600

•

Liverpool

Source1 Solutions

(315) 730-5667

•

•

•

Medford

American Environments Co.

(631) 736-5883

•

• • • • •

• •

Medina

TREK, Inc.

(585) 798-3140

Melville

Underwriters Laboratories, Inc.

(631) 271-6200

•

•

Northport

Mohr, R.J., Assoc., Inc.

(631) 754-1142

Owego

Lockheed Martin Federal Systems

(607) 751-2938

• • •

•

•

Poughkeepsie

IBM Corp. Poughkeepsie EMC Lab

(607) 752-2225

•

•

Rochester

Chomerics, Div. of Parker Hannifin

(781) 939-4158

•

Rochester

Spec-Hardened Systems

(585) 225-2857

• • • • •

Retlif Testing Laboratories

(631) 737-1500

• • • • • • • • •

• • • • •

• •

New York

• • • •

•

•

•

• • • • •

• •

•

• • •

•

• • • • •

•

•

• •

•

•

•

• •

• •

•

• • •

•

Ronkonkoma

North Carolina Cary

CertifiGroup

(800) 422-1651

•

•

Fayetteville

Partnership for Defense Innovation R&D Lab (910) 307-3000

•

•

•

•

Greensboro

Electrical South, LP

(800) 950-9550

•

Greenville

Lawrence Behr Associates (LBA)

(252) 757-0279

•

• •

•

New Bern

iNARTE, Inc.

(252) 672-0111

•

Raleigh

MicroCraft Corporation

(919) 872-2272

• • •

• • •

• •

•

• •

Res. Triangle Pk. Educated Design & Dev., Inc. (ED&D)

(919) 469-9434

•

• •

•

Res. Triangle Pk. IBM RTP EMC Test Labs

(919) 543-0837

•

•

•

Res. Triangle Pk.

(919) 549-1400

•

•

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• •

•

28

Underwriters Laboratories, Inc.

interference technology

emc test & design guide 2010

& canada

City

Company Name

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Youngsville

Flextronics International EMC Labs

(919) 554-0901

• • • • • • • • • •

• •

Brooklyn Heights Sypris Test & Measurement

(216) 741-7040

•

Burton

F-Squared Laboratories, Inc.

(877) 405-1580

• • • • • • • • •

•

•

Chesterland

EU Compliance Services, Inc.

(440) 918-1425

•

• • •

•

• •

Cleveland

CSA International

(216) 524-4990

•

•

Cleveland

NASA GRC EMI Lab

(216) 433-2533

•

•

Cleveland

Smith Electronics

(440) 526-4386

•

• • •

•

Fairborn

Sypris Test & Measurement

(937) 427-3444

•

Mason

L-3 Communications Cincinnati Electronics

(513) 573-6809

Springboro

Pioneer Automotive Technologies

(937) 746-6600

Integrated Sciences, Inc.

(918) 493-3399

Beaverton

Tektronix

Hillsboro Hillsboro

•

Ohio

•

•

•

•

•

•

•

•

•

•

• •

•

(407) 551-2738

•

•

•

Cascade TEK

(503) 648-1818

•

ElectroMagnetic Investigations, LLC

(503) 466-1160

•

Portland

Northwest EMC, Inc.

(888) 364-2378

• •

Portland

TÜV SÜD America, Inc.

(503) 598-7580

•

Tillamook

ElectroMagnetic Investigations, LLC

(503) 466-1160

•

Oklahoma Tulsa

Oregon

•

•

• • •

•

• •

•

•

•

• •

•

•

•

•

•

Pennsylvania Annville

CHAR Services, Inc.

(717) 867-2788

• •

•

Boalsburg

Seven Mountains Scientific, Inc.

(814) 466-6559

•

•

•

Glenside

Electro-Tech Systems, Inc.

(215) 887-2196

•

•

•

Harleysville

Retlif Testing Laboratories

(215) 256-4133

• • • • • • • • •

• • • • •

Hatfield

Laboratory Testing, Inc.

(800) 219-9095

New Castle

Keystone Compliance

(724) 657-9940

•

• • • • •

Norristown

LCR Electronics, Inc.

(610) 278-0840

•

Pottstown

BEC Inc.

(610) 970-6880

•

• • •

W. Conshohocken Alion Science & Technology/R&B Lab

(610) 825-1960

• • •

• •

• •

•

•

Willow Grove

Nelson Design Services

(215) 784-9600

Knoxville

Global Testing Labs LLC

(865) 525-0137

•

Knoxville

Southern Testing Services, Inc.

(865) 966-5330

•

• • • • • •

• • • • •

• •

•

•

• •

•

•

• •

•

•

•

•

•

•

Tennessee

interferencetechnology.com

interference technology

29

City

TX

Company Name

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Contact

Texas Austin

Austin EMC

(512) 219-6650

•

•

•

Austin

BAE Systems IDS Test Services

(512) 929-2410

•

•

Cedar Park

TDK RF Solutions, Inc.

(512) 258-9478

•

Euless

Ronald G. Jones, P.E.

(817) 267-1476

•

•

•

Houston

DNV Certification

(281) 721-6600

•

Lewisville

Nemko USA

(972) 436-9600

• •

• • • • •

• • • • •

• •

Plano

National Technical Systems (NTS)

(972) 509-2566

• • • • • • • • • •

• •

•

• •

Plano

Intertek Testing Services

Richardson

Sypris Test & Measurement

(972) 202-8800

• • • • •

•

• •

(972) 231-4443

•

Round Rock San Antonio

Professional Testing (EMI), Inc.

(512) 244-3371

•

• • •

• • •

Southwest Research Institute

(210) 684-5111

•

Coalville

DNB Engineering, Inc.

(435) 336-4433

•

•

Ogden

Little Mountain Test Facility (LMTF)

(801) 315-2320

• • •

• • • • •

•

•

•

•

• •

• • • • • • • • • • • •

•

• •

Utah

30

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• •

•

•

• •

emc test & design guide 2010

& canada BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

City

Company Name

Contact

Salt Lake City

Communication Certification Laboratory

(801) 972-6146

•

Salt Lake City

L3 Communication Systems–West

(801) 594-2560

•

Essex Junction

Huber & Suhner

(802) 878-0555

Middlebury

Green Mountain Electromagnetics, Inc.

(802) 388-3390

Falls Church

Raytheon Prototype Services

(703) 849-1562

•

Fredericksburg

Vitatech Engineering, LLC

(540) 286-1984

•

•

Herndon

Rhein Tech Laboratories, Inc.

(703) 689-0368

•

McLean

American TCB

(703) 847-4700

• •

Reston

TEMPEST, Inc. (VA)

(703) 709-9543

•

Richmond

Technology International, Inc.

(804) 794-4144

• • • • • • •

• • • •

•

Vermont •

• • •

•

• •

Virginia

•

• • •

• • • • •

•

•

• •

• • •

• •

• • • • •

•

• •

•

• •

• •

• •

•

• • •

• • •

• •

•

Washington Acme

Acme Testing Company

(360) 595-2785

Bothell

CKC Laboratories, Inc

(425) 402-1717

Sultan

Northwest EMC, Inc.

(888) 364-2378

•

Butler

Emission Control, Ltd.

(262) 790-0092

•

Cedarburg

L.S. Research

(262) 375-4400

• •

Genoa City

D.L.S. Electronic Systems, Inc.

(847) 537-6400

• •

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•

• •

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Wisconsin •

•

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Jo Pr

Lic 97 Br US

+1 FA JF ww N2

628 LeVander Way S. St. Paul, MN 55075

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City

Company Name

Contact

BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI T LI GH Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I SHI -160 ON ELD TEM ING EF PES FECT T IVEN ESS

2011 emc test lab directory

Milwaukee

Curtis Industries/Filter Networks

(414) 649-4200

•

Neenah

International Compliance Laboratories

(920) 720-5555

• • • • •

•

•

•

•

•

Canada Alberta

Airdrie

Electronics Test Centre - MPB Technologies (403) 912-0037

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•

• • •

•

• •

Calgary

EMSCAN Corporation

(403) 291 0313

•

•

Calgary

National Technical Systems (NTS)

(403) 568-6605

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• •

Medley

Aerospace Engrg. Test Establishment (DND) (780) 840-8000

•

•

• • • • •

•

British Columbia Abbotsford

Protocol EMC

(604) 218-1762

• • •

• •

Kelowna

Celltech Labs, Inc.

(250) 765-7650

• •

• • • • •

• •

•

Pitt Meadows

Tranzeo EMC Labs Inc.

(604) 460-4453

•

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•

Richmond

LabTest Certification, Inc.

(604) 247-0444

• • • • • • •

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Kanata

Electronics Test Centre

(613) 599-6800

•

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Merrickville

EMC Consulting, Inc.

(613) 269-4247

• • • • •

• • • •

Missisauga

Intertek ETL Semko

(905) 678-7820

•

•

•

•

Nepean

APREL Laboratories

(613) 820-2730

•

• •

Nepean

Multilek Inc.

(613) 226-2365

•

Oakville

Ultratech Group of Labs

(905) 829-1570

•

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Ottawa

ASR Technologies

(613) 737-2026

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Ontario

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•

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Ottawa

Nemko

(613) 737-9680

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Ottawa

Power & Controls Engineering Ltd.

(613) 829-0820

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• •

•

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Ottawa

Raymond EMC Enclosures Limited

(800) EMC-1495

• •

Scarborough

Vican Electronics

(416) 412-2111

•

Toronto

CSA International

(866) 797-4272

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Toronto

Global EMC Inc.

(905) 883-8189

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Quebec Montreal

Centre de Recherche Industrielle du Quebec (514) 383-1550

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Quebec

Comlab, Inc.

(418) 682-3380

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Quebec

FISO Technologies

(418) 688-8065

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The listings above— Interference Technology’s “2011 EMC Test Lab Directory”—are our effort to provide our readers with accurate and current information on the vast number of testing capabilities available. We also realize that events move swiftly in the testing sector and that new services are added on a regular basis. If, after reading the Directory, you notice an inaccurate inclusion or omission, please join the effort for accuracy by forwarding the details to slong@interferencetechnology.com.

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emc test & design guide 2010

& canada BEL LCOR Cb/ E/TEL COR cab EMI /TCB DIA SSIO E M P NS /LI G ESD HTNIN G EF FEC eur TS oC ERT IFIC FCC ATIO PAR FCC T 15 & Ns PAR 18 T IMM 68 UNI LI GH T Y TN I N M I L G ST R -STD I KE MIL 188/ -STD 125 NVL 461/4 62 AP/ PRO A2L A A D UC PPRO RAD T SAFE VED TY HA RS0 Z TESTI NG 3> 2 repai 00 V/ MET r/C ER A RTC A DO LIBRAT I O -1 N 6 SHI ELD 0 TEM ING EF PES FECT T IVEN ESS

u n i t e d s tat e s

Suppliers of Filters & Ferrites

Suppliers of Amplifiers City

Company Name

Contact

AR Worldwide RF/Microwave Instrumentation; Souderton, PA 215-723-8181; 800-933-8181; www.ar-worldwide.com

Americor Electronics, Ltd.; Elk Grove Village, IL; 847-956-6200 www.americor-usa.com

CPI (Communications & Power Industries) Canada Inc.; Georgetown, ON, Canada; 905-877-0161; www.cpii.com/cmp

Fair-Rite Products Corp.; Wallkill, NY; 888-324-7748 www.fair-rite.com

Instruments for Industry; Ronkonkoma, NY; 631-467-8400 www.ifi.com

Radius Power Inc.; Orange, CA; 714-289-0055 www.radiuspower.com

Suppliers of Antennas

Schurter Inc.; Santa Rosa, CA; 707-636-3000 www.schurterinc.com AH Systems; Chatsworth, CA; 818-998-0223 www.AHSystems.com

Suppliers of Shielding Suppliers of Conductive Materials

Magnetic Shield Corporation; Bensenville, IL; 888-766-7800 www.magnetic-shield.com

Dontech Incorporated; Doylestown, PA; 215-348-5010 www.dontechinc.com

Spira Manufacturing Corporation; N. Hollywood, CA 818-764-8222; www.spira-emi.com

Swift Textile Metalizing LLC; Bloomfield CT; 860-243-1122 www.swift-textile.com

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33

Suppliers of Shielding

Your weekly EMC update!

roducts for Your ing Needs

Interference Technology eNews brings you a weekly dose of:

Spectrum Control; Fairview, PA; 814-474-2207 www.spectrumcontrol.com

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Inc.; Plymouth, MA; up 508-747-0300 Log PeriodicTech-Etch, Antenna Passive Horns to 40 GHz www.tech-etch.com

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Suppliers of Test Equipment g e Pricin v i t i t e p ngle Source Com Delivery nty t s a F liance testing. ra ear War ustry, and very Three-y Advanced Test Equipment Rentals; San Diego, CA; 800-404-ATEC www.ATECorp .com

ntables • Masts & Tripods • Product Safety Accessories

power.com

00 • fax 714.528.1992 • sales@com-power.com Com-Power Corporation; Brea, CA; 714-528-8800

www.com-power.com

EM TEST AG; Reinach, Switzerland; +41 61 717 91 91 www.emtest.com

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emc test & design guide 2010

testing & test equipment

EMC P e r f o r m a n ce O v e r a L i f e t i me

EMC Performance of a Product Over Its Lifetime

gert gremmen, tim haynes, ralph mcdiarmid, Ed price, john woodgate

E

MC performance of a product is likely to vary with age as the physical characteristics change, e.g. caps dry out and metal junctions oxidize, etc. Obviously, the product is designed with the intention of consistent compliance over the life of the product, but are there any requirements or guidance relating to preventing or controlling this change in EMC performance over time?

This question posed recently on a product safety forum garnered some interesting responses from EMC and product safety experts. Interference Technology delved a little deeper and asked a panel of experts their thoughts on the topic: Can environmental factors that jeopardize EMC over a product’s lifetime result in performance, reliability and even safety implications? gremmen: Yes, but it will need a risk analysis in the design phase to identify the risks associated with aging. That risk analysis should include the whole spectrum of aging aspects, from components, to soldering techniques, contact properties related to oxidation, moisture, vibration, but also need to incorporate equipment properties that are not expected to “age”, such as software.

The analysis also needs to consider

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changing properties that at first sight do not impact EMC properties, such as enclosures of which radiation patterns and resonance properties may change and have a bigger impact on EMI as initially assumed.

Ultimately, it is impossible to maintain EMC properties over a long time, and therefore a definition of the lifetime of a piece of equipment is required. Very little work has been done on the calculation of lifetime for electronics in general, but a lot of data on failure rates is available, for example, in soldered contacts, and individual components. I have been involved in developing a simple method of creating a lifetime expectation based on collected statistical data for component lifetimes, but that does not include many relevant aspects, such as enclosure lifetime under miscellaneous (hards) conditions.

PRICE: In the military product area, most products don’t live long enough for aging to be as important as the (usually) very hostile physical environment. One further specific instance is damage to cable / backshell junctions due to abuse by users and/or vibration and shock.

Haynes: Expanding only slightly, corrosion can reduce screening at interfaces of boxes, cables, connectors etc., gaskets can deteriorate, components can age and affect EMI performance.

Can lifetime reliability be better assured by simulating product aging emc test & design guide 2010

testing & test equipment

INT E RF E R E N C E T E C HNOL O G Y

to environmental testing specialists, and start collecting events, and try to couple this to EMC properties. A knowledge base may be created that allows designers to identify potential risks.

before EMC testing is done? How can lifetime EMC integrity be assured when equipment is still generally tested only once?

Woodgate: It depends on how realistic the simulation is, given that no simulation can be wholly realistic.

[Lifetime EMC integrity can be assured] by careful selection of components, operating them well below their maximum stresses and careful overall design (e.g., assure continued integrity of seams in enclosures).

Mcdiarmid: In my brief experience in private industry (since 1983) I can recall only one legitimate complaint concerning radio interference from a product. It’s my experience that EMC problems during operational service of a product designed and verified through type testing to comply with the applicable standards is a rare thing, even over its operational lifetime. It may be that most products functionally fail and are removed from service before they become an EMC nuisance.

Many companies control the configuration of their products by keeping a list of EMC critical components, much like a list of safety critical components for use in UL and CSA compliance. If a component, like a power MOSFET, needs to change manufacturer, then all the specifications are carefully checked and an EMC retest (at least for emissions) may be performed before qualifying the alternate source.

If a product complies with the applicable RF emission and immunity standards, it will likely never be a problem during its lifetime.

Haynes: Some requirements (possibly customer requirements in defence/aerospace) need environmental testing (heat cycling / vibration) to be completed before EMC tests are undertaken. No “repairs” are allowed between environmental and EMC testing.

PRICE: In a Qualification test scenario, it is our practice to run the temp cycling, vibration, humidity types of tests before the system goes to EMC. True, some tests (high-G shock, blowing rain, transportation shock, high-G centrifuge) are often done on a separate system. gremmen: I am not aware of simulation software with a view on EMC related to aging. I think that in order to incorporate aging as a factor in EMC, we need to lend a ear

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testing & test equipment

EMC P e r f o r m a n ce O v e r a L i f e t i me

Are there any regulatory requirements to artificially age a product prior to EMC testing? If so, are the requirements industry specific?

Gert Gremmen is a senior test engineer in EMC and product safety for electronic and electrical products, director of ce-test qualified testing bv in the Netherlands and an expert in CE marking.

Woodgate: Not for commercial products in Europe, as far as I am aware.

Direct controls of performance are not appropriate for safety-critical applications. Each product has its requirements set by following a procedure, which is described in the multi-part standard IEC 61508.

Tim Haynes, electromagnetic engineering specialist at SELEX S&AS, has worked on space systems, avionics, marine and submarine equipment for the defense industry and has employed forensic techniques in resolving problems, in particular EMC issues during design and development of hardware.

Haynes: There may be some implicit requirements, such as in section 6 of the UK Health and Safety at Work Etc. Act 1974 - Duties Towards Articles Used At Work. There may be other such requirements in legislation (possibly in the Provision and Use of Work Equipment?). There may also be requirements in Joint Airworthiness Requirements (JARs) that require a ground-based “golden sample” aircraft to be exposed to more hours of simulated flying than the worstcase flight-cleared aircraft of the type. This is to identify fatigue failures in the ground-based model before they can happen in the flight-cleared aircraft.

Ralph McDiarmid, AScT, has 12 years experience in power electronics circuit design and simulation - converers and inverters to 3kW - and 10 years experience with regulatory international product approvals, including CSA, UL and CE.

PRICE: USA military procurements are controlled by a strict and extremely specific list of contractually obligating “Line Items”, so this is all defined by the contract. gremmen: There are no such regulations I am aware of. At least there are no such for ordinary commercial and residential equipment, not even for high-end laboratory equipment.

Ed Price, a NARTE certified EMC engineer, has worked in the Electromagnetic Compatibility Lab at Cubic Defense Applications in San Diego, Calif. since 1993.

Can a well-defined maintenance schedule help ensure regular surveillance of components that will affect the EMC performance of a product?

Woodgate: Possibly: Some EMC characteristics can be checked simply enough for inclusion in a maintenance schedule (e.g. low-frequency conducted emissions), while others cannot (e.g. high-frequency immunity). Some might think that ESD immunity could be checked in a maintenance process, but this raises safety issues in itself.

John Woodgate of J.M. Woodgate and Associates has a background in the consumer products and sound reinforcement sectors of the electronics industry, as well as product management and marketing of audio, high fidelity and video products. He became an independent consultant in 1984.

Haynes: Yes - but only where there is a conscientious maintainer. This may be much more important in respect of vehicle maintenance (screening of the engine management unit, braking control, etc.), than it would be to have annual maintenance on your TV or washing machine. However, how many garage mechanics would be trained in “EMC”?

* Participants’ comments do not necessarily reflect the views of their employers.

PRICE: Military systems have several levels of maintenance, with the first line generally not going beyond “pull that box that doesn’t work and put in a new one.” First level people are usually not opening boxes, fixing cables or doing other intrusive things. At the depot level, a manufacturer should specify if EMC items should be replaced as part of maintenance (perhaps a particular EMI gasket is good for only a few open/close cycles).

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gremmen: Applications that require tight control of EMC properties during a defined lifetime definitely need adequate service. Maintenance has traditionally been focused on functional parameters only, even in aerospace and aviation technology. Many EMC-related components can get defective without even being noticed in functional testing, so additional testing has to be defined in order to recognize potential failures of this kind. While emission

emc test & design guide 2010

testing & test equipment

INT E RF E R E N C E T E C HNOL O G Y

gremmen: Many EMC properties of equipment are undefined in the design phase. If a problem during initial testing is found, remedial measures such as filters may help controlling emissions. However, the source of the problems is not under control. A change of manufacturer for a microprocessor, for example, may change emission levels to a high degree, even if the component is pin and specification compatible. The EMC properties of such a component are in general not specified in a datasheet. A newer process on chip level, or even change of location of manufacture may impact those properties. The manufacturer is not bound to notice their customers, as EMC properties go undocumented. I lately witness a large number of SMPS related problems in EMI where just the ongoing progress in FET developments results in much faster switching times as before, creating substantial interference problems in the 30-200 MHz range. The manufacturers of the switchers, confronted with the problem, told us that they had updated their switching FETS as older (tested) models quickly became obsolete and the FET manufacturer provided them with equivalents and pin compatible models with a faster switching time. Even software can have an impact on EMC; simple changes in firmware (updates) can create sudden changes in emissions or immunity behavior that are completely outside the view of the software designers.

properties may be quickly established using, for example, a tabletop spectrum analyzer on a comparative basis (compared to a new piece of equipment), immunity problems will remain unnoticed until a full test suite for immunity has been carried out. As many EMC components have a function towards common mode phenomena, traditional test techniques that use differential mode signals are not capable of detecting failures in such components. A surge suppressor, for example, may be connected to the enclosure and not to system signal ground, and may look connected to nothing from the point of view of traditional automated test sets. In addition to that, commercial test setups for components operate on PCB level, and not on equipment or even system level.

Even with regulatory and contractual compliance established at the outset, could changes be made to a product that may compromise its EMC performance?

Woodgate: If you mean ‘changes during life’, the answer must be ‘yes’. [This can be avoided by] total encapsulation, making the product unrepairable. But then how can the heat be dissipated? Heat pipes? Such ‘heroic’ measures are hardly justified.

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testing & test equipment

EMC P e r f o r m a n ce O v e r a L i f e t i me

Woodgate: It’s far too LATE at the onset of testing.

These requirements must be applied at the outset of DESIGN, where they pay a dividend of around 1000%.

Given the fact that modern software development heavily depends on external modules and libraries, such changes may even be unnoticed to the manufacturer of the product.

Again, EMC properties of the building blocks of electronic are most of the time undocumented.

And yes, during testing it is too late. Too many definite choices have been made at that point already.

Haynes: There is much greater benefit to be obtained by considering ALL environment and EMC requirements that will apply during the product lifecycle at the very beginning - at the concept stage of the product/project.

Haynes: A rack of equipment installed in an EMC cabinet passes the required tests with the doors closed. The customer can use the equipment with the doors closed but they are always open because he wants to see the flashing lights and alpha/numeric displays to ensure the equipment is working ...

To limit customer-based changes - design products that are actually fit-for-purpose - or should that be fit-for-theusers-purpose. Otherwise implement measures to prevent EMC features being “overridden”.

PRICE: I think everybody says it’s good to plan ahead. gremmen: Yes, if EMC is recognized to have a substantial impact on reliability and safety, taking in consideration all these aspects will create benefits for both manufacturers as well as consumers.

Do you have any anecdotal examples that illustrate the above points or would be helpful to fellow engineers?

PRICE: Keep close to your customer so they can accidentally show you all the new and exciting things they do with your product. You will learn the most interesting things.

Haynes: Some radio equipment was EMC tested after vibration and thermal testing had been successfully completed. The equipment failed EMC on emissions and immunity. The cause was “cracked” semi-rigid coax / connector joints where either vibration or thermal expansion had caused the connector to cable-sheath interface to crack, causing the transfer impedance to increase and allow signals into / out of the coax cable. If the equipment had not been vibration / thermal tested before the EMC - this failure would not have been found.

Is there a benefit to considering environmental and EMC requirements at the outset of testing a product?

PRICE: Same scenario; this time finding connector nuts that were improperly torqued and allowed the connectors to loosen. n

Europe EMC Guide Now Online The online edition of the 2011 Interference Technology Europe EMC Guide will be updated periodically during 2010/2011.

Subscribe online to receive notification of these edition updates.

www.interferencetechnology.eu

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emc test & design guide 2010

testing & test equipment

U S B I n t e r f a c e o n L a b o r at o r y S u r g e G e n e r at o r s

USB Interface on Laboratory Surge Generators

Jeffrey D. Lind Compliance West, USA Del Mar, CA

A

s any laboratory engineer knows, harsh, noisy lab environments often result in data loss and/or resets of test equipment or host computers. A potential solution to this challenge is the successful implementation of mains power distribution in the lab, and an isolated serial/USB design for laboratory computer systems. This will allow the lab to utilize the strengths of both the computer’s USB interface and the laboratory equipment's existing serial interface technology.

The advent of USB controlled devices in the laboratory has been a boon in many ways. “Plug and play” devices make installation easy, and ubiquitous USB connectivity on modern laptops and desktop computers allow powerful data processing to be available easily. The speed of modern USB connections, USB 2.0 and above, allow realtime data collection. The hot-swappable feature allows technicians to change setups at will without worrying about restarting the computer.

USB connectivity does not always need to be used for real-time data collection.

The convenience lends itself to other uses as well. For simpler installations, the interface between the test equipment and the personal computer is used only for control of the test equipment, to provide test equipment status for display on the computer 42

interference technology

screen for operator convenience, or for basic housekeeping information, in which the computer is updated by the test equipment regarding its actions. In this case, the speed advantages of the USB interface are not realized, but the convenience of connection still makes the USB interface a good choice.

In many cases, operators who are rushed for time may not investigate a non-USB connection because these non-swappable interfaces require research or reboot, taking valuable time. If an operator is presented with the USB interface, which is a known commodity, he may be more willing to plug it in and enjoy the conveniences that were written into the interface.

In addition, the serial ports on computers are no longer standard. In most cases, the serial and parallel ports which used to be supplied have been deleted in favor of more USB ports to connect to keyboards, printers, monitors, thumb drives and most everything else. So, in addition to the conveniences of the USB interface, there is a practical requirement to use USB connections because other connection protocols are simply disappearing from personal computers.

With this set of features and conveniences, as well as the issue regarding disappearing alternatives, the USB interface should be making RS-232 and GPIB installations obsolete. However, this is not the case at many laboratories and these older installations are still the norm.

As can be seen from Table 1, the existemc Test & design guide 2010

testing & test equipment

Lind

ing laboratory interface protocols all suffer from disadvantages which affect their usefulness in a laboratory environment. USB can offer distinct advantages but is not robust. The USB reset can exhibit loss of communication between the test equipment and the computer, or in some cases a reboot of the personal computer connected to it. These conditions would preclude the USB interface from consideration in a laboratory environment, if the advantages were not so great. The usefulness of the USB interface certainly merits work toward making the interface more robust, so it can be used with interference-causing equipment such as surge generators, hipot testers and other similar equipment.

Design Considerations Serial interfaces use positive and negative voltages for data transmission, so the effects of changes in ground potential are negated. This is a larger problem for USB, because the data

Interface

Advantages

Disadvantages

• More noise-resistant

• 115 kbs max speed • Serial interface not available on many personal computers

Parallel

• User Familiarity

• 115 kbs max speed • Setup difficult • Parallel interface ports disappearing from personal computers

GPIB

• Large installed base • Fast • Error-Resistant

• Interface Card Required • Expensive • Proprietary setups

USB

• Fast • Plug and Play • Available on Personal Computers • Hot Swappable • Easy Set Up • Cheap

• Reset-Prone • Noise susceptibility

RS-232

Table 1. Overview of interface protocols used in laboratory environments.

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testing & test equipment

U S B I n t e r f a c e o n L a b o r at o r y S u r g e G e n e r at o r s

Figure 2. The proper method of connecting mains power to a computer-controlled surge tester. The surge tester and the computer are provided with individual paths to ground.

Figure 3. Improper mains connection method. The surge tester and the computer share a grounding path. If the ground voltage rises due to the surge tester output, the USB connection may suffer a reset, and the computer could be damaged.

transmission uses a positive voltage and ground only. Therefore, noise and ground potential changes have a greater effect, and this is the reason that USB interfaces have to be more carefully implemented for a good result.

In the days of RS-232 interface communications, there was 6 volts minimum swing between binary zero (-3V maximum) and binary one (+3V minimum). Since the voltage has to swing through ground potential, a 44 

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shifting ground voltage had little effect on RS-232 communications. RS232 did not have any error checking protocols but because of the robust hardware solution, it was not needed to make reliable connections. However, even with this robust signal communication, a shielded cable was required, as external noise could overpower the RS-232 communication. Clearly, a more sophisticated protocol with error checking was going to be needed

as noise in the laboratory increased.

USB communication has many protocols, and many incorporate error checking, which should have been a boon to communication in noisy environments such as laboratories.

Unfortunately, USB communication design presents challenges for interface designers and users. Since the difference between a binary zero (+0.3 V maximum) and binary 1 (+2.8V minimum) is only 2.5V, and the because the zero is approximately ground referenced, the USB interface is more susceptible to disconnects and resets, which could result in a complete hardware collapse, where communication between the test equipment and the computer is totally lost. This will result in loss of control of the tester, and loss of data across the link. In general, the designer of the USB interface of the equipment must select a protocol that will detect a disconnect, reconnect the interface, and make sure the USB connection was recovered. Further, its design must include optical interface(s) to prevent varying voltage levels from causing data loss. Some interfaces use a dedicated microprocessor in order to allow even more isolation between the computer and the test equipment.

Grounding of Test Equipment and Computers Even the most isolated design will still have to deal with the equipment grounding conductor, or ground lead.

In the case of a powerful surge generator, the ground plane can be displaced by as much as a few volts, which could cause interface disconnection and data loss. This happens because the surge tester can deliver thousands of amps in a few microseconds and this energy needs to be dissipated to the building ground. Any high resistance connections within the test setup or in the building grounding system itself can cause a rise in potential of the grounding lead for a short time while the energy is dissipated.

To combat this problem, it is necessary to make sure the building grounding system and the test setup ground leads are all in working order emc Test & design guide 2010

testing & test equipment

Lind

and firmly connected together. This step will solve many data loss and reset problems between computers and general test equipment, but in the case of surge test equipment, we recommend separation of the power lines (mains) of the computer and the test equipment, as shown in Figure 2. This step allows the ground current to flow separately from the test equipment to building ground, and not influence the ground potential of the computer. A separate ground for the test equipment will solve most USB reset problems. In order to clearly illustrate the point, Figure 3 presents an incorrect mains implementation, which has a greater chance of causing resets in the USB interface.

USB-Serial Interfaces In many cases, it is not possible to run separate mains circuits to laboratory test equipment to prevent resets of the USB interface. There is another method which has solved problems, and that is to employ a hybrid interface, consisting of a RS-232 serial interface on the test equipment with a proprietary circuit which changes the protocol from RS-232 to USB before presented to the computer.

This allows all the benefits of the USB interface to be used by the personal computer, and also allows the robust RS-232 interface to be used on the test equipment.

Location of the protocol change is important. Because of the strength of the RS-232 communication, the change to USB should be done as close to the computer end of the cable as possible. In addition, optoisolation of the interface change is imperative. This unfortunately leaves most commercial solutions out of consideration, as their unisolated interface changer is located at the RS-232 end of the cable.

mains voltage of the computer, in accordance with Figure 2 of this article, NOT Figure 3. In addition, an isolated hybrid interface consisting of RS-232 protocol at the test equipment end and USB protocol at the computer end should also be employed. The isolated interface should be located as close to the computer end of the cable as possible.

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emc design / filters

C l o c k i n g S t r at e g i e s f o r EMI R e d u c t i o n

Clocking Strategies for EMI Reduction

SASSAN TABATABAEI SiTime Corporation Sunnyvale, CA

I. INTRODUCTION lectronic devices have to operate in close proximity, whether it is in the home, office, industrial establishment, or outdoors. Each of the devices may radiate electromagnetic energy, which can interfere with the operation of the rest of the devices.

To avoid such harmful interference, governments and industry bodies limit the amount of energy that any device can radiate. Environmental compliance standards such as FCC Class A and B specify these limits for different categories of equipment, based on the location of end use.

One of the key sources of electromagnetic interference (EMI) energy is the clock tree. Good design and layout of the clock tree ensures that the system not only performs well without major timing issues, but also ensures the system passes environmental compliance standards. Careful consideration must be given to the following: • The clock source and associated traces • The circuits that are the driven with the clock. These circuits may consist of a number of discrete devices, but more often than not, it includes a small number of large integrated circuits (ICs) that perform most of the key functions for that application.

• The I/O circuitry and traces that exchange data from one IC to another or to external systems.

Each trace (clock or data) can be considered a transmission line and different kinds of traces have varying characteristics.

E

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Transmission line theory is well-established in the electronics industry, so we will not go into that detail in this paper.

The main reason for EMI radiation is lack of signal return path in transmission lines. This typically occurs when there is a discontinuity in the ground or signal return plane underneath the clock and signal traces. The EMI energy is typically concentrated at the clock frequency and its harmonics. The energy at higher harmonics depends on the clock signal shape. Because most clock signals have near square-wave shape with finite slew rate, the harmonics of the signal do play an important role in EMI. Generally, faster slew rates and overshoots/ undershoots due to inadequate termination result in larger EMI at the frequencies of the harmonics.

The main EMI reduction techniques are as follows: 1. Shielding 2. Using solid ground or signal return path for high-speed signals 3. Signal filtering 4. Reducing rise/fall time 5. Using spread-spectrum clocking (SSC) modulation Shielding requires enclosing the system in a grounded conductive box to block the radiation of energy to the outside. In many consumer and computing applications, such enclosures are costly or are impractical due to the physical constraint of the system. The use of a solid ground is a recommended design practice for not only reducing EMI, but also for maintaining good signal integrity in high-speed signal paths. However, small amounts of energy will radiate even in the presence of a solid ground from the top side of the trace. In some high density boards, emc test & design guide 2010

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C l o c k i n g S t r at e g i e s f o r EMI R e d u c t i o n

Figure 1. Clock signal harmonic amplitude decreases as the rise/fall time increases.

Rise times are normalized to the clock period.

it may be difficult to guarantee a solid ground or return path for all signals without adding extra ground layers, which increases the board cost.

The following sections discuss the remaining three techniques in greater detail.

II. SIGNAL FILTERING FOR EMI REDUCTION EMI may radiate from the signal output pins and traces. Typically, much of such radiation is from the board traces because the board traces are longer than the clock device pins or internal IC traces. In some cases, the short traces in the large IC packages can dominate the EMI at relatively high frequencies (greater than 500 MHz).

Using low pass filters at the highspeed clock and data outputs effectively attenuates the signal frequency content, especially at high harmonics.

Typically, simple RC-based low pass filters are used due to their simplicity, low cost, and small board space requirement. A RC filter is a single pole filter with 3dB attenuation at its cutoff frequency and 20dB/dec attenuation for frequencies above that. The cutoff frequency has to be approximately twice that of the clock frequency to avoid reducing the signal swing too much; otherwise the signal swing may violate the logic threshold of the receiver digital circuits. This filter is 48

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suitable for reducing EMI at high harmonics; for example, it provides 20dB attenuation at the 11th harmonic of a clock signal. It is possible to design more complex filters, such as second order ones to attenuate higher harmonics even more, but they are more bulky and expensive.

Filtering technique has the following disadvantages: 1. The board designer has to place the filters at the dominant EMI signal outputs, but it is often difficult to identify those signals. In designs where one clock source is driving one or two main ICs, placing the filter on the clock signal may be effective solutions.

2. Low pass filters do not offer much EMI reduction at the main clock frequency and first two or three harmonics.

3. The filters present resistive and capacitive load to the output drivers, which in turn increase the power consumption. The resistive current can be estimated by dividing the signal DC level by the equivalent resistor at the output. The capacitive current is computed as CVF, where C is the equivalent capacitance at the output, V is the voltage swing, and F is the clock frequency.

4. The RC filters take board space and increase the cost. This is especially true if separate filters have to be used for multiple signals traces.

III. EMI REDUCTION THROUGH RISE/FALL TIME CONTROL Reducing rise/fall time for singleended clocks and signals is an effective way of reducing harmonic EMI. Figure 1 shows the amplitude of clock harmonics as a function of rise/fall time (rise and fall times are assumed to be the same). All the rise times are selected to maintain the peak-to-peak clock signal to its maximum value.

As this figure shows, most harmonics can be reduced by 20dB or greater while maintaining the peak-to-peak clock swing. As such, the rise/fall time reduction provides better harmonic EMI reduction than RC filters without sacrificing the voltage swing.

Most single-ended drivers, such as LVCMOS, consist of push-pull circuits.

In such circuits, the maximum drive capability of the driver and the effective load capacitance define the rise/fall time. Therefore, there are two ways to increase the rise/fall time: • Increase the load capacitance. This method has the disadvantage of increasing current consumption.

• Decrease the output current drive.

This method does not increase the current consumption, but requires the clock device output drive strength to be programmable.

Some clock devices and output buffers in the large ICs allow drive strength adjustment. Examples include programmable oscillators.

The main disadvantages of this EMI reduction method are: • It only reduces clock harmonic EMI, and • It may not be possible to reduce the rise/fall time sufficiently for highspeed clocks and signals.

IV. EMI REDUCTION USING SPREAD-SPECTRUM CLOCKING (SSC) Waveform shaping methods, such as filtering and rise/fall control are ineffective for reducing the EMI generated at the main harmonic from the clock traces. Additionally, they do not decrease EMI from the chipsets and traces that are driven by buffers without filters or rise/fall time adjustment.

In addition to the clock traces, the data emc test & design guide 2010

emc design / filters

Ta b ata b a e i

EMC SINE wave output filters

lines may also radiate energy. Such energy is attenuated by the random nature of the data signals, but it may still exceed acceptable levels because there are typically many more data signals in a system than clock ones.

Board designers use slew rate control and proper transmission line design to reduce EMI, but due to large number of sources, the residual EMI at main frequency and its harmonics may still be high. In such cases, spread spectrum clocking is an effective system-wide EMI reduction solution.

SSC is implemented by modulating the clock signal with a low rate frequency modulation. The modulation spreads the clock energy over a larger bandwidth, which reduces the maximum power for a given spectral bandwidth. The most common spectral bandwidth for measuring the peak EMI is 100 kHz, as defined by the federal communication commission (FCC). The SSC modulation rate in most applications is 32 kHz to provide fairly flat response in the region over which the carrier frequency is spread.

The most commonly used modulation profiles is the triangular one, as shown in Figure 2b. This profile effectively distributes the carrier frequency energy uniformly over the modulation range and provides a fairly flat spectrum at the clock frequency and its harmonics. Sinusoidal modulation does not provide the same flatness due to A)its non-uniform frequency distribution. Figure 2c shows Hershey-Kiss shaped modulation profile, which offers optimally flat carrier spectrum. This profile offers 1.5dB less peak EMI than triangular modulation, but it is more complex to implement.

Assuming that the clock frequency is modulated by a given percentage, SSCpercentage, and that the percentage harmonic spectrum is fairly flat after SSC nodulation, the peak energy reduction can be approximated as below: where, ASSC(i) is the amplitude of the clock i-th harmonic amplitude after SSC modulation, f SSC _range is the frequency

A)

U

B)

U U

U

I

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I

I

I

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range that the clock harmonic spreads over after SSC modulation, Aclk (i) is the clock i-th harmonic amplitude before SSC modulation, and RBW is the bandwidth for measuring EMI energy. The f SSC _range is computed as f SSC _ = fclk (i).SSCpercentage. Therefore, range the EMI reduction at the i-th harmonic can be computed as below: ASSC(i)(dB) = Aclk(i)(dB) −10log10(SSCpercentage. fclk(i)/ RBW ) This equation indicates that the larger the clock frequency, the larger the EMI reduction. Also, the EMI at the higher harmonics of the clock are reduced more than the lower ones.

The SSC modulation profile can be centered on the non-SSC clock frequency, or be less than the non-SSC clock frequency. The former is called center-spread, and the latter down-spread. The down-spread ensures that the SSC modulation does not cause periods shorter than those interferencetechnology.com

U U

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emc design / filters

C l o c k i n g S t r at e g i e s f o r EMI R e d u c t i o n

Figure 2. SSC modulation profiles.

of the clock without the SSC modulation. This is especially important for processor applications to ensure that that clock period does not violate the critical path timing in the internal state machines of the processor. The

down-spread, however, leads to an average frequency that can vary over a large range, e.g., a few hundred parts per million (ppm). Such large average frequency variation may result in buffer overflow in some I/O systems.

The center-spread guarantees more accurate average frequency, but leads to short periods. For center-spread modulation, the user has to ensure that the processor and state machines are rated for the maximum frequency of the clock with SSC. The advantage is easier buffer management in the I/O systems.

Figure 3 and Figure 4 show the EMI reduction for the measured main harmonic of 12 MHz and 125 MHz clocks, respectively. The modulation range is 2% and modulation profile is triangular in both cases. These figures clearly show that the higher the clock frequency, the larger the EMI reduction. Figure 5 and Figure 6 show the EMI reduction for the first, third, fifth, and seventh harmonics of a 100 MHz clocks with 2% down-spread triangular modulation. They indicate that the EMI at higher harmonics are reduced more than that of lower harmonics.

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emc test & design guide 2010

emc design / filters

Ta b ata b a e i

SSC is used widely in certain applications, such as printers and microcontroller applications because it offers the following advantages: 1. Reduced cost: a. No need to use expensive shielding techniques. b. Recued ground layers. It may be difficult to ensure that all data and clock signals have uninterrupted ground plane underneath, which lead to EMI radiation from some traces. One solution is to add ground plane layers, but that adds board cost. SSC technique can reduce EMI and save additional ground planes.

2. F lexibility: A system may be designed with non-SSC clocks. If the EMI testing shows EMI issues, the oscillator can be replaced with SSC ones to reduce EMI without changing anything else in the system.

Also, the SSC percentage may be adjusted to the minimum needed to meet EMI goals. This will minimize

Figure 3. Main harmonic spectrum for a 12 MHz clock with and without 2% down-spread triangular SSC modulation.

the impact on the system timing margins.

3. System-wide EMI reduction. Other EMI reduction approaches, such as

filtering, waveform shaping, ground plane continuity, and shielding reduce EMI at the specific places where this techniques are used. In

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C l o c k i n g S t r at e g i e s f o r EMI R e d u c t i o n

Figure 4. Main harmonic spectrum for a 125 MHz clock with and without 2% down-spread triangular SSC modulation.

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contrast, adding SSC to the clock, reduces EMI from all signals that are synchronous with that clock regardless of their locations.

SSC modulation, however, is not always a solution to EMI problems in the following situations: 1. SSC modulation increases period jitter. For example, in 100MHz clock with 1% SSC modulation, the peakto-peak period jitter increase by 1% of the clock period, or 100ps. When center-spread is used, some periods are shorter than the ones without SSC, which may violate the critical path timing in digital circuits. To avoid this issue, down-spread is often the preferred SSC type because it guarantees that no clock period becomes shorter than the ones without SSC. 2. Deeper I/O buffers and more complex buffer management required.

Many systems use two different clocks at the data source, e.g., a processor, and data sink, e.g., peripheral device. Since the clocks are not synchronous, the sink needs to buffer received data and avoid loosing data. Also, the sink has to include some type of buffer management protocol to ensure it can adjust for the rate difference between its clock and the source one. When SSC is used, the buffer depth and management protocol has to be able to accommodate significant variable difference between source and sink clock rate. For example, the sink may ignore or insert some bits between transmission packets to adjust the rate difference dynamically. The I/O standard that allow such protocols optionally include DDR2, DDR3, PCI, PCI-X, PCI-Express, Serial ATA (SATA), fully-buffered DIMM (FBDIMM). The more recent USB3.0 standard includes SSC as a mandatory feature. Using SSC modulation for other types of I/O that do not include specific buffering features is generally not recommended.

SSC clock jitter performance is often specified using the concept of cycle-to-cycle jitter. C2C jitter is defined as the variation of one cycle of a clock signal relative to its adjacent emc test & design guide 2010

emc design / filters

Ta b ata b a e i

cycle. Because the SSC modulation rate is typically very low, the impact of the SSC on two adjacent cycles is very similar, and hence their difference is very insensitive to the SSC modulation.

It can be shown that the SSC-induced phase modulation is filtered with a filter response that has a 3dB corner frequency and ¼ of the clock frequency and attenuation rate of 40dB/dec at low frequency offset [1]. This ensures that C2C capture the jitter at higher frequency offsets and excludes SSCinduced jitter. As such, it captures the impact of clock jitter in terms of critical path timing more effectively.

Figure 5. First and third harmonic spectrum for a 100 MHz clock with and without 2% downspread triangular SSC modulation.

V. CONCLUSIONS EMI radiation may result in significant interference of one electronic system to other systems close by. To ensure multiple systems can operate properly in close proximity, EMI radiation from each system has to meet limits defined by industry or government bodies. Major EMI reduction

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C l o c k i n g S t r at e g i e s f o r EMI R e d u c t i o n

techniques include: 1. Shielding 2. Signal filtering 3. Using solid ground or signal return path for high-speed signals 4. Reducing rise/fall time 5. Using spread-spectrum clocking (SSC) modulation The shielding can be costly, and sometimes difficult to accommodate due to the physical constraints of the system. Signal filtering requires additional board space and components, and can also increase power consumption. Ensuring solid ground is an effective method, which should be followed as a good board layout design practice. However, it is not always a practical solution because it can lead to more ground plane layers, which increases cost. Rise/fall time reduction is a very effective method for reducing EMI at high harmonics without increasing power consumption or requiring additional board components.

However, such method is only possible if the clock and data buffers and I/Os provide rise/ Figure 6. Fifth and seventh harmonic spectrum for a 100 MHz clock with and without fall time adjustment.

2% downspread triangular SSC modulation.

All the methods above are localized to the specific traces. In contrast, SSC modulation reduces EMI system-wide because the modulation is distributed to all the signal that stem from the SSC clock, regardless of where that are located. It also reduces EMI at both main harmonics and high harmonics. The main drawback of SSC modulation is that its use is limited to system that use I/O interfaces that include buffer management features required for handling the dynamic rate variations caused by the SSC modulation. For example, it cannot be used for Ethernet and high-speed USB2.0 I/Os. REFERENCES • [1] Office of Engineering and Technology, “Understanding the FCC regulations for low-power, non-licensed transmitters”, Federal Communication Commission, OET Bulletin, No. 63, October 1993.

• [2] K. Harding, R. A. Oglesbee, F. Fisher, “Investigation into the interference potential of spread-spectrum clock generation to broadband digital communications”, IEEE Transaction on Electromagnetic Compatibility, Vol. 45, No. 1, February 2003.

• [3] H. Skinner, K. Slattery, “Why spread spectrum clocking of computing devices is not cheating”, IEEE International Symposium on Electromagnetic Compatibility, 2001.

SASSAN TABATABAEI has held the position of Director of Strategic Applications at SiTime Corporation since 2008. Prior to that, he held executive and technical management positions at Guide Technology, Virage Logic, and Vector12.

He received his Ph.D. from the University of British Columbia, Vancouver, BC, Canada in Electrical Engineering in 2000. n

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emc test & design guide 2010

lightning, transients & esd

H E RNIK

How Smaller Form Factors Exacerbate ESD Risks and How Foil Resistors Can Help YUVAL HERNIK Vishay Precision Group Malvern, PA

F

or most of us, electrostatic discharge (ESD) and static electricity are little more than the shocks received when touching a metal doorknob after walking along a carpeted floor, or when opening a car door. The level of the voltage produced depends on a number of factors, such as the affinity of the two bodies and the air humidity. Even so, these “harmless” shocks can reach values over 25,000 V. ESD can be defined as a rapid transfer of charge between bodies at different electrical potentials - either by direct contact, arcing, or induction - in an attempt to become electrically neutral. The human threshold for feeling an ESD is only around 3000 V, so any discharge that can be felt is above this voltage level. Because the duration of this high voltage spike is less than a microsecond long, the net energy is small compared to the size of the human body over which it is spread. From the human body’s point of view, ESD does no harm. But when the discharge is across a small electronic deTABLE 1 - E LECTRICAL SPECIFICATIONS OF FOIL AND THIN FILM CHIPS vice, the relative energy density is so great that RANGE OF OHMIC many components can PRODUCT BEST TCR, VALUES, ALL CHIP be damaged by ESD at TECHNOLOGY MIL. RANGE SIZES levels as low as 3000 V or even 500 V. 5Ω to 150 kΩ Bulk Metal Foil 0.2 ppm/°C ESD damage can occur at any stage of a 30Ω to 3 MΩ Thin Film 10 ppm/°C component’s life, from interferencetechnology.com

manufacturing to service. For many years it was thought that semiconductor components such as diodes and transistors were particularly susceptible to ESD, but now we know that passive components such as resistors can sometimes be more sensitive to ESD than active components. Unless specific precautions are taken, a wide range of electronic components can be damaged by ESD. The most common cause of ESD damage is direct transfer of an electric charge from either a human body or a charged material to an ESD-sensitive (ESDS) device.

Resistors and ESD In resistors, ESD sensitivity is a function of size, value, physical construction and thickness. The smaller the resistor, the less space there is to spread the energy caused by an ESD pulse. When this energy is concentrated in a small area of a resistor’s active element, and in particular where there is a high current density or “hot spot,” the resistive element may heat up to the point of sustaining irreversible damage. With the growing trend of miniaturization, electronic devices, including resistors, are becoming smaller and smaller, causing them to be more prone to ESD damage. Resistance changes due to ESD damage, like load-induced changes, are permanent and can either increase or decrease the device’s resistance value depending upon the resistor’s design and technology. interference technology

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H o w S m a l l e r F o r m F a c t o r s E x a c e r b at e E S D R i s k s

Three Categories of ESD Damage • Parametric Failure: Parametric failure occurs when the ESD event alters one or more device parameters (resistance in the case of resistors), causing it to shift from its required tolerance. This failure does not directly pertain to functionality; thus a parametric failure may be present even if the device is still functional. For example, if a 10 kΩ resistor with a 1 % tolerance undergoes an ESD event that changes its resistance to 11 kΩ (a 10 % deviation), the device would still be able to function as a resistor. But now its parameters have been altered, and it is no longer suitable for its original function. The consequences of such changes may not be immediately apparent but rather may manifest themselves only during circuit temperature excursions, thermal shocks, load life, or any other parametric-shifting influence that would normally be accommodated through error-envelope planning for net accumulated shift limitations.

• Catastrophic Damage: Catastrophic damage has occurred when the ESD event causes the device to immediately stop functioning. This may occur after one or a number of ESD events with diverse causes, such as human body discharge or the mere presence of an electrostatic field.

• Latent Damage: Latent damage has occurred when the ESD event causes moderate damage to the device, which is not noticeable, as the device appears to be functioning correctly. However, the load life of the device has been dramatically reduced, and further degradation caused by operating stresses may cause the device to fail during service. Latent damage is the source for greatest concern, since it is very difficult to detect by re-measurement or by visual inspection, since damage may have occurred under the external coating.

The three most common resistor technologies are Thin Film, Thick Film, and Bulk Metal Foil. Each has specific characteristics related to ESD sensitivity.

• Thin Film resistors are composed of a metal layer that is only a few hundred angstroms thick. This severely limits the device’s capability to withstand the energy that is passed through it during an electrostatic discharge, causing it to be very sensitive to ESD damage. As a result, Thin Film resistors are sensitive to energy and can experience value changes of up to 5 % before the ESD causes the film to rupture or to melt.

• Thick Film resistors are comprised of a random dispersion of conducting metal particles within a non-conducting particulate medium, usually ceramic; hence they are also known as “cermet” resistors. Current through the resistor follows along the random contacts formed among the metal particles. Power surges cause breakdowns in some of the inter-particulate isolation, thereby reducing resistance by establishing new additional current paths.

Thus, ESD surges almost always cause a reduction in resistance. This fact is so well established that Thick Film manufacturers use controlled power surges to tune the resistors to the required resistance and tolerance, which typically ranges from 5% to 20%. The susceptibility to change does not stop at manufacture and the resistor is subject to similar changes every time the resistor experiences an ESD event. ESD-induced changes while in service can cause resistance changes up to 50%, which is easily sufficient to cause a malfunction.

• Bulk Metal Foil resistors have a number of characteristics that make them superior to both Thin and Thick Film when it comes to withstanding ESD. Bulk Metal Foil resistors are comprised of a single layer of special metal alloy rolled into a foil and mounted on a high thermal conductivity ceramic substrate with maximum foil-ceramic interface contact for maximum eduction of heat. As a foil, the molecular structure of the resistance element is the same as the base alloy and therefore has the same metallurgical stability and the same ability to withstand power surges and long-term drift. The foil is 100 times thicker than Thin Film, and therefore the heat capacity of the resistive foil layer is much higher compared to the Thin Film resistive layer.

Resistor Technologies and ESD Sensitivity Different resistor technologies exhibit various levels of sensitivity to ESD damage. Damage to an ESDS device depends on the device’s ability to dissipate energy and withstand the energy of the voltage levels involved, and in resistors is generally exhibited by a change in the electrical resistance of the device. This is especially crucial in resistors requiring high precision and reliability.

TABLE 2 - CHIP RESISTOR STYLES, ASSIGNED ESD TEST VOLTAGE AND ENERGY DENSITY STYLE

RESISTIVE LAYER’S DIMENTIONS[1] (mm)

LAYER’S AREA (mm 2 )

ESD TEST VOLTAGE [2] (V)

ESD ENERGY [EmJ]

ENERGY DENSITY (E mJ/mm 2 )

METRIC

INCHES

RR1005M

RR0402

0.5 x 0.5

0.25

500

0.019

0.076

RR1608M

RR0603

1 x 0.8

0.8

1000

0.075

0.094

RR2012M

RR0805

1.4 x 1.2

1.7

1500

0.169

0.100

RR3216M

RR1206

2 x 1.6

3.2

2000

0.300

0.094

RR5025M

RR2010

4 x 2.5

10

3000

0.675

0.068

NOTES: [1] Approximate dimensions of the part of chip’s surface occupied by the pattern, in mm

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[2] Per draft Iinternational Standard prEN140401-801:200X emc test & design guide 2010

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H E RNIK

Testing Resistors for ESD Sensitivity Manufacturers test for ESD sensitivity (ESDS) per customer request, but usually do not publish ESDS specifications in their data sheets. However, the ESD of precision chip resistors depends on the following: • Resistive material • Production technology (Thick Film, Thin Film, or Foil) • Chip size • Ohmic value • Resistive layer’s thickness • Resistor’s construction • Design of the resistive pattern In testing the influence of above factors, the results depend also on the test method used.

Table 1 shows typical specifications for two main technologies used in production of high precision surface mounted chip resistors: Bulk Metal Foil and Thin Film.

Bulk Metal Foil chips are produced by cementing a nickel-chromium alloy

foil, rolled to a thickness between 2 and 10 microns, to a ceramic substrate. Thin Film chip production involves deposition (by evaporation, sputtering or similar methods) on a ceramic substrate of a film, mainly nickel-chromium or Tantalum Nitride. A typical thickness of the Thin Film layer is about 1/100 of the Bulk Metal Foil.

Table 2 represents chips which are made in standardized sizes, in rectangular shapes. In the middle of the rectangle is a pattern formed in the resistive layer of foil or Thin Film, connected on two sides to two termination pads.

Tables 3, 4, and 5 show the results of ESD tests on Thin Film, Thick Film, and Foil resistor chips. The superiority of Bulk Metal® foil precision resistors over Thin Film, when subjected to ESD, is attributed mainly to their greater thickness (foil is typically 100 times thicker than Thin Film), and therefore the heat capacity of the resistive foil layer is much higher compared to the Thin Film layer. Thin Film is created

through particle deposition processes (evaporation or sputtering), while foil is a bulk alloy with a crystalline structure created through hot and cold rolling of the melt. Tests show that Bulk Metal Foil chip resistors can withstand ESD events above 25 000 V, while Thin Film chip resistors have been seen to undergo catastrophic failures at electric potentials as low as 3000 V and parametric failures at even lower voltages. If the application is likely to confront the resistor with ESD pulses of significant magnitude, the best resistor choice is Bulk Metal Foil.

Conclusions • When it comes to withstanding ESD, Foil resistors have a clear advantage over Thin Film chips.

• Foil chips can handle an order of magnitude more ESD energy than Thin Film chips without experiencing a change in their resistance.

• The standard for ESD protection in chip resistors ranges from 1 kV to

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lightning, transients & esd

H o w S m a l l e r F o r m F a c t o r s E x a c e r b at e E S D R i s k s

TABLE 3 - 2kV ESD DISCHARGE - COMPARISON OF DEVIATIONS, FOIL VS. THIN FILM DISTRIBUTION OF 20 CHIPS BY % OF DEVIATION AFTER ESD DISCHARGE TYPE AND VALUE

>0.5 %

0.2% to 0.5 %

0.1% to 0.2 %

0.05% to 0.1 %

0.02% to 0.05 %

0.01% to 0.02 %

<0.01 %

FOIL 30 Ω TF1, 30 Ω TF2, 30 Ω FOIL 1000 Ω TF1, 1000 Ω TF2, 1000 Ω

0 12 0 0 20 20

0 8 1 0 0 0

0 0 1 0 0 0

0 0 2 0 0 0

1 0 8 0 0 0

6 0 4 0 0 0

13 0 4 20 0 0

TABLE 4 - 3kV ESD DISCHARGE - COMPARISON OF DEVIATIONS, FOIL VS. THIN FILM DISTRIBUTION OF 20 CHIPS BY % OF DEVIATION AFTER ESD DISCHARGE TYPE AND VALUE

>0.5 %

0.2% to 0.5 %

0.1% to 0.2 %

0.05% to 0.1 %

0.02% to 0.05 %

0.1% to 0.02 %

<0.01 %

FOIL 30 Ω TF2, 30 Ω

0 4

0 10

0 3

0 2

1 1

8 -

11 -

FOIL, 1000 Ω

0

0

0

0

0

0

20

TABLE 5 - 24kV ESD DISCHARGE - COMPARISON OF DEVIATIONS, FOIL VS. THIN FILM DISTRIBUTION OF 20 CHIPS BY % OF DEVIATION AFTER ESD DISCHARGE TYPE AND VALUE

>0.5 %

0.2% to 0.5 %

0.1% to 0.2 %

0.05% to 0.1 %

0.02% to 0.05 %

0.01% to 0.02 %

<0.01 %

FOIL, 30 Ω

0

0

1

1

14

3

1

FOIL, 1000 Ω

0

0

0

0

0

0

20

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emc test & design guide 2010

lightning, transients & esd

H E RNIK

3 kV, but Bulk Metal Foil resistors can handle ESD pulses up to 24 kV with no significant shift in resistance (measured shifts were less than 0.1 % for a 30-Ω resistor and less than 0.01 % for a 1000-Ω resistor) • Thin film chips from different sources and with different values show non-uniform behavior with respect to ESD. This may be due to a pattern design that was not optimized for ESD, or a non-uniform film deposition process, or a substrate material that was not of the best quality.

APPENDIX Standards for ESD Testing Of Chip Resistors • The international standard IEC 61340-3-1 describes the testing of electronic components for ESD compatibility by using the Human Body Model (HBM).

• A test simulator generates an adjustable voltage ESD pulse by discharging a 150 pF capacitor to the device under

test (DUT) with a discharge resistor of 330 Ω connected in series.

• The ESD exponential waveform which was calibrated with a discharge resistance of 330 + 2 Ω will have a time constant which is twice as long when the DUT is a resistor of 332 Ω and much longer with a high ohmic value DUT. Test voltages are listed in table 2. The limit of allowed change of resistance is set for all chip stability levels at 0.5 % + 0.05 Ω.

• RC time constant = (330 + 2) x 150 x 10-12 Ω x (s/Ω) = 49.8 x ns (compared to 150 ns, per ANSI standard).

Energy of ESD Absorbed By a Resistor Chip • The ESD is simulated by charging a capacitor of C = 150 pF to a specified voltage V. • The stored energy E = 0.5 CV2 is discharged into two resistors connected in series: discharge resistor RDIS of 330 Ω representing the resistance of a human body and RDUT - of the DUT,

in our case the tested chip. As a result, the following voltage VDUT and energy EDUT are applied to the chip: • VDUT = V x RDUT /(330 + RDUT) • EDUT = E x RDUT /(330 + RDUT) References • [1] Thiet The Lai: Electrostatic Discharge (ESD) Sensitivity of thin-Film Hybrid Passive Components. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, Vol.12, No. 4, December 1989.

• [2] International Standard EN 140401-801:2002 • [3] F. Zandman et al.: Resistor Theory and Technology, SciTek Publishing, Inc. 2002 • [4] Technical Note “ESD Sensitivity of Precision Chip Resistors Comparison between Foil and thin Film Chips” By Joseph Szwarc, 2008 • [5] Vishay Technical Note “Resistor Sensitivity to Electrostatic Discharge (ESD)” By Yuval Hernik 2007 YUVAL HERNIK holds a B.Sc in electrical engineering from the Technion (Israel Institute of Technology). He has been a director of application engineering at Vishay Precision Group— Bulk Metal Foil resistors—since 2008. n

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59

telecom

MIL- S T D 462/461E C o m pa r ed t o MIL- S T D 461F Test S et U p

Understanding the Changes to FCC 5 GHz Part 15.407 Regulations

david A. CASE Cisco Systems Richfield, OH

I

n July of 2003, the International Telecommunications Union – Radio adopted Recommendation 229, allocating the 5150-5350 MHz and 5470-5725 MHz bands to mobile service, including RLAN systems .

The following year the FCC updated its Part 15.407 regulations to include the 54705725 MHz band, as well as require changes for devices that operate in the 5250-5350 MHz band. As part of sharing the bands with other services on a non-interference basis, the RLAN systems are required to use TPC (Transmitter Power Control) and DFS (Dynamic Frequency Selection), both Cognitive Radio Techniques .

Reported problems in the field During discussions on CRS /SDR issues at WP5a in late 2008, there was some discussion on RLAN possibly interfering with radar systems despite DFS. However, nothing concrete was presented at these meetings. In April of 2009, it was reported that the FCC was holding up applications for new grants for 5GHz systems specifically in the DFS bands.

In discussions with the FCC lab, the problem told to industry was that there were a number of FAA Terminal Doppler Weather Radars that were being interfered with by RLAN systems and that until the investigation was complete and a possible solution found, no further approvals would

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As of October 15, the FCC has turned on the certification process for systems that operate in the 5GHz DFS bands and operate outdoors. Additional information can be found in the FCC KDB 443999. be granted for these systems.

Interference was to the TDWRs from RLAN operating in the 5600-5650 MHz band specifically, as well as some interference from systems operating on the channels adjacent to this band.

It was discovered that, in some cases, the users could select different country settings and actually turn off DFS; in other cases, the device could only detect the very specific waveforms of the test procedure.

Interim solution An ad-hoc industry workgroup was formed by interested parties and after a series of discussions with member companies.

Since the systems causing the interference were outdoor systems, based on discussions with members of the industry, the FCC released in October 2009 an interim procedure for approving master devices operating in these bands indoors.

The requirements for the indoor systems operating in the 5470-5725 MHz are as follows per FCC KDB 443999: 1) The device must not be able to operate on the 5600–5650 MHz band 2) The device must be marketed and sold for indoor use only 3) The information on indoor use only in the 5470-5725 MHz needs to be in the manual or on a label on the device emc Test & design guide 2010

telecom

C a se Frequency band

TDWR >35 km

TDWR <35 km

5470-5725 MHz

5600-5650 MHz band off

5600-5650 MHz band off

5470-5725 MHz

Registration not required

Register in Database

• D evices must meet all of the other requirements specified in Section 15.407, and no configuration controls (e.g. country code settings or other options to modify DFS functions) may be provided to change the frequency of operations to any frequency other than those specified on the grant of certification for US operation.

• A ll applications must clearly show compliance with all of the technical requirements under worse case parameters under user or operator control based on frame rates, listen/talk ratios and user data transfer conditions.

• The next phase will be to develop new radar waveforms for the DFS testing which would test the ability of the systems to detect these TDWR systems. To this effort the industry, the FCC and NTIA are meeting to discuss and review requirements. Further NTIA will be doing some additional testing of the WLAN systems against the new radar wave forms.

As the issues progresses it is best to check with the FCC lab on status of approvals of outdoor systems and also to keep up to date on changes via possibly new FCC KDB’s.

4) The end user cannot have access to controls set to other regulatory domains or country settings nor be able to turn off DFS The above FCC KDB allowed the process for indoor-only devices to be turned on and then the focus was on outdoor devices. This issue was addressed in a several tier approach.

The first was that the FAA and FCC were investigating the interference and tracking down these systems. In some cases where either the products were non compliant or that the operator made unauthorized changes, fines were assessed.

In cases where the systems were compliant, the systems were set to other frequencies to avoid causing problems.

Second, the FCC issued a Public Notice from OET and Enforcement Bureau asking all manufacturers to reach out to their customers and inform them of this issue. As part of this effort, a voluntary database has been developed that allows operators and installers to register the location information of the UNII devices operating outdoors in the 5470–5725 MHz band when they are installed within 35 km of any TDWR location. The manufacturers are conducting an outreach to their customers as part of this effort to help resolve the interference issues. (See http://www. spectrumbridge.com/udia/home.aspx).

The third solution is to work towards a goal to allow the approvals of outdoor RLAN operating in the 54705725 MHz band to go forward. This is being done in a multi-step solution. The first is the interim procedure which is the next revision of KDB 443999. This document was sent out for comments and the comments are now being reviewed by the FCC. The proposal is as follows as extracted from FCC KDB: 1. Devices will not permit operation on channels which overlap the 5600 – 5650 MHz band.

2. Devices intended for outdoor use will be further restricted, as follows: • Devices must be professionally installed when operating in the 5470 – 5725 MHz band, • Grantees must provide owners, operators and all such installers with specific instructions in their user’s manual on requirements to avoid interference TDWR and information that meet the following instructions: • A ny installation within 35 km of a TDWR location shall be separated by at least 30 MHz (center-tocenter) from TDWR operating frequency (as shown in the attached table), 4, and • Procedures must be provided for the installers and the operators on how to register the devices in the industry-sponsored database with the appropriate information regarding the location and operation of the device and installer information in that database. interferencetechnology.com

DAVID A. CASE, NCE, NCT, is senior regulatory engineer, corporate compliance EMC standards and operations, for Cisco Systems Inc. in Richfield, Ohio. He can be reached at davecase@cisco.com. n

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D i f f e r e n t i a l Tr a n s f e r I m p e d a n c e o f S h i e l d e d T w i s t e d P a i r s

Differential Transfer Impedance of Shielded Twisted Pairs

Michel Mardiguian Private EMC Consultant St Rémy lès Chevreuse, France

T

he concept of Shield Transfer Impedance Zt, introduced by S. Schelkunoff in 1934, is a very convenient parameter for prediction & control of EMI coupling through cable shields. Although widely applied to coaxial cables against EMI susceptility problems, the Zt parameter can be easily extended to coaxial cables EMI emissions problems, as well as to Shielded Twisted Pairs (STP). This latter is more specifically addressed here, through the concept of Differential Transfer Impedance (Ztd).

I. Brush-up on Transfer Impedance Zt Until a few decades ago, the Shielding Effectiveness (SE) of a cable was defined more or less in the same manner as for a Faraday cage or any shielded enclosure, as the ratio of the E (or H) field outside to the E (or H ) field inside. More exactly, the field that would exist at a given point if the shield was not there, to the remaining field when the shield is in place.

In practice, with a shielded cable, the effects of the incident field are measured instead: that is the voltage (or current) induced on an unshielded wire illuminated by a given field, to the voltage (or current) on a shielded version of a similar conductor.

Although the principle looks sound and simple, providing a SE figure in dB, the measurement itself is not so easy, requiring the

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interference technology

making of a strong electromagnetic field, hence a set of RF amplifiers and antennas, in a shielded - preferrably anechoic- room.

Like any radiated EMC measurement, it is plagued with a substantial uncertainty ( typ. 6 dB), aggravated by the fact that below 50MHz, for 1m antenna distance, the test falls in near-field conditions. In such case, the measured SE will depend on the type of antenna being used : E-field illumination will give flattering results, while H-field (loop antenna) will produce overly severe results. Furthermore, test variables like the cable height and its terminating resistors are introducing poorly controlled effects.

In summary, the SE of a same sample, measured by a radiated method could vary widely from one test configuration to another, leaving the user with a SE figure which may not be transposable to his specific application.

Instead of an SE figure which is installation-dependent, the EMC Community has, since long, privileged a parameter that is intrinsic to the cable shield and to nothing else. This is accomplished by the Transfer Impedance (Zt), a brilliant concept introduced by Schelkunoff around 1934-38[1].

The transfer impedance relates the current flowing on a shield surface to the voltage it develops on the other side of this surface. This voltage is due to a current coupling through the shield thickness (if the shield is a solid tube, this diffusion rapidly becomes unmeasurable, due to skin effect, as frequency increases) and to the leakage inductance through the braid’s holes. The better the quality of the braid, the less the longitudinal shield’s voltage. emc test & design guide 2010

shielding

D i f f e r e n t i a l Tr a n s f e r I m p e d a n c e o f S h i e l d e d T w i s t e d P a i r s

Zt is easy to measure, using a conducted injection set-up, less prone to errors and unaccuracies than a radiated test. A current Is (Figure 1) forced on the shield by a generator or current clamp inserted in the cableto-ground loop. Because of shield imperfections (shield resistance and braiding interstices) a small voltage appears in the inner space between the center conductor and the shield. This voltage, or a fraction of it, is measured at the end of the cable, connected to a Spectrum Analyzer or Oscilloscope input.

The result is normalized to a 1 meter long sample, such as: Zt (Ω/m) = Vi (Volt) / (Ish x l m) (1) where.

Vi = l o ngitudinal voltage induced inside the shield over length « l », causing a noise current to circulate in the center conductor Ish = external current injected into the shield by the EMI source If the cable is terminated at both ends in loads R L matched to its characteristic impedance, each end takes one half of the full induced voltage Vi. Finally: Zt (Ω/m) = 2 x V L/ ( Ish x lm ) Typical values of Z t for various coaxial cables are shown in Figure 2.

If the shield is grounded by pigtails (a poor practice) the pigtails impedances must be added to Zt, and to the loop impedance calculations. Below about 100kHz, Zt remains constant, being merely the shield’s ohmic resistance.

Above 1 MHz, typically for a single braid, Zt increases with frequency, due to the leakage inductance Lt between the overall braid and the inner conductor. For a good single layer braid, Lt ranges around 1nH /m.

So, Zt can be expressed in the frequency domain as: Zt (Ω/m) = Rsh (Ω/m) + j ωLt (Henry/m)

Figure 1. The concept of transfer impedance.

II. Using Zt in susceptibility prediction for a coaxial cable Initially, Z t was conceived for susceptibility calculations against a known EMI threat, for instance an ambient field illuminating the

Figure 2. Typical values of transfer impedance, Zt.

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shielding

D i f f e r e n t i a l Tr a n s f e r I m p e d a n c e o f S h i e l d e d T w i s t e d P a i r s

Figure 3. Principle of coaxial cable driven into radiation.

Vi = (Zt x lm) x Ish (3) If the EMI frequency is such as the cable length exceeds λ/2, then the physical length « l » should be replaced by λ/2 in the bracket term of Equation 3.

Example 1: A 4m single braid coaxial cable, installed 0.75m above ground, is illuminated by an ambient RF field of 10V/m @ 15MHz, causing 9V of open loop induced voltage. What is the voltage appearing at the receiver end of the cable?

External loop impedance, calculated by Equation 2:

Zext = (0.01 + j 5 x 15 MHz) x 4m = 300Ω The calculated loop current is:

Ish = 9V / 300Ω = 0.03A For a single braid coax. like RG58, Figure 2 indicates Zt @ 15MHz = 0.15Ω/m.

The induced voltage on the coax center conductor is:

Vi = Zt x l m x I = 0.15 x 4 x 0.03 = 18mV Assuming that the cable is terminated in 50Ω both ends,

V L = 18mV x 50 / (50 + 50) = 9mV If the receiving endwas terminated in a high impedance, like 5kΩ :

V L = 18mV x 5000 / (5000 + 50) ≈ 18mV Incidentally, one could grade the reduction factor gained via the shield as the ratio of the loop bulk voltage to the voltage appearing internally: Kr = 9V / 18.10 -3 V = 500, that is 54dB

cable-to-ground loop area. The impedance of this external loop, for a single-braid coaxial with an outer diameter in the 5 to 15 mm range, and at a height of 50 to 500 mm above ground can be approximated by: (2) Zext = ( 10 mΩ + j 5 Ω x FMHz) per meter length If the field-to-loop induced voltage is known, this ground-loop impedance can be used to calculate the loop current Ish circulating on the shield. Knowing Ish, Zt can then be used straightforward to estimate the voltage appearing inside the shield :

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II. Using Zt for predicting radiated RF emissions from a coaxial cable The principle of Zt is perfectly reciprocal and can be applied to emissions as well. RF signals, baseband video, some LAN links and other high-frequency signals are carried over coaxial cables. A very small fraction of the intentional signal current (typically 0.3 to 0.1 percent above a few MHz) returns by paths other than the shield itself (Figure 3). This assumes that the shield is at least correctly tied to the ground references at both ends, and preferably also to the chassis by the coaxial connectors.

The signal current I0 returning by the shield’s inner side is causing an EMI voltage to appear along the outer side.

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shielding

D i f f e r e n t i a l Tr a n s f e r I m p e d a n c e o f S h i e l d e d T w i s t e d P a i r s

This voltage is given by: Vext = Zt (Ω/m) x l (m) x I0

(4) = Zt (Ω/m) x l (m) x V0 / ZL In turn, this voltage Vext is causing an external current to excite the antenna formed by the cable-to-ground loop, hence radiating a small field that can be associated with the quality of the shield and its installation.

For estimating the E and H field from this low-impedance loop (see Figure 4), the external shield current can be found by:

Iext = Vext / Zext where Zext is the same as the one calculated for susceptibility case. Eventually, pigtail or connector impedances have to be incorporated into Zext. Although their contribution to Zext is usually minimal, they can seriously deteriorate the shield transfer impedance, since Zt must be hundreds or thousands of times smaller than Zext, for a good shield.

If the shield is floated from the chassis, the shield becomes an electrically driven radiator. The radiated field can be calculated using monopole or dipole equations, with Vext, as an input.

When the cable becomes electrically long, Zt (Ω/m) no longer can be multiplied by the length, since the current is not uniform along the cable shield. A default approximation is to consider that the maximum amplitudes of the shield voltages distributed along the shield are:

Figure 4. Equivalent circuit to predict coaxial cable radiation.

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emc test & design guide 2010

shielding

Mardiguian

Vext (max) = Iext. Zt (Ω/m) x λ/2 (5) So, as Zt increases with frequency, the effective length which multiplies Zt decreases with frequency. At the same time, the cable-to-ground external impedance needs to be replaced by ZC, the corresponding characteristic impedance, using the following formula:

ZC = 60 logn (4h/d) (6) Example 2 A 2 meter piece of RG-58 coax is connecting two cabinets, with BNC connectors at both ends. The electrical parameters are:

Useful signal: 15 MHz video

Load resistance: 75Ω

V0 spectrum amplitudes:

fundamental (15MHz) = 10 Vpk

harmonic #3 ( 45MHz) = 3.3 Vpk

harmonic #5 ( 75MHz) = 2 Vpk The geometry is: Cable diameter= 0.5 cm, height above ground = 30 cm Calculate the radiated field at 3 m due to harmonic #3.

Solution First, we need to determine the area of the radiating loop:

A = 2 m x 0.3 m = 0.6 m2 = 6,000 cm2 For 45MHz, λ = 6.70m, so the 2m length of cable is already exceeding λ/4 , approaching λ/2. We can consider that the radiation efficiency of the antenna formed by the

shield-to-ground loop has reached its maximum asymptote.

For a same reason, the external loop impedance is approaching its maximum, that is the characteristic impedance :

ZC = 60 log n (4 x 30 / 5) = 330 Ω The internal signal current returning by the shield is:

I0 (45MHz) = V0 /75 Ω = 3.3 / 75 = 44mA The external shield voltage, due to transfer impedance Zt is :

Vext (45MHz) = I0. Zt(Ω/m) x 2m, where Zt (45MHz) is given by Figure 2 = 0,4 Ω/m

Vext = 44.10 -3 . 0.4 . 2m = 35. 10 -3 V This voltage, in turn, is driving an external current onto the loop: Iext = Vext / ZC = 35. 10 -3 V / 330Ω = 107.10 -6A From this current, the radiated field at 3 m (far field conditions) can be quickly estimated [2] by :

E (µV/m) = [ 1.3 . Acm2 . Iamp . F(MHz) 2 ] 1/D

E (µV/m) = 560 µV/m , or 55dBµV/m (*Note: Since the whole calculation has been carried in peak values, 3dB should be subtracted for peak-to-rms conversion, but they are apprximately offset by the ground plane reflection of the CISPR/FCC test set-up.)

Although this radiated level is about 500 times lower than if a bare wire were carrying the same current with a return by the ground plane, FCC Class B limit is exceeded

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by 15 dB @ 45MHz, with other limit violations at 75, 105 MHz and so on.

Several possibilities exist to reduce the radiated field: • Select a coaxial cable with a lower Zt, like “optimized” braided shields (thicker, denser braid) or double-braid shield.

• Slip a large ferrite bead over the cable shield. It will take an added series impedance of about 1,200Ω to achieve the required attenuation, for instance passing the cable twice into a large ferrite toroïd.

• Reduce the cable height above ground.

shield Zt which is a distributed parameter (Ω/m), Zct is a localized element.

Of course, if the shield is grounded by a piece of wire, or « pigtail » ( a very poor practice), the connecting impedance is simply the self-inductance of this wire tail.

The following Table values can be taken for typical impedances of one single shield connection:

III. Importance of the Shield Connections As important as a shield with low Zt is its low-impedance termination to the equipment metal boxes. The connection by which the shield itself is grounded to the equipment box (or PCB) has its own impedance, too.

This impedance consist of the shield-to-backshell contact, the connector-to-receptacle impedance (that may include some seam leakage inductance) and the receptacleto-chassis contact resistance.

This connection impedance Z ct is directly in the signal current return path, in series with Zt. Therefore, Zct can increase seriously the voltage Vext, which excites the cable-to-ground radiating loop. At contrast with cable

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Pigtail, 2.5 cm

Z = 1.5 mΩ + j. 0.15Ω x FMHz

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IV. The Differential Transfer Impedance (Ztd) with Shielded Pairs or Multiconductor Cables The concept of transfer impedance, used for radiated susceptibility or emission modeling of a coaxial cable, is transposable to shielded twisted pairs (STP). However, there is a noticeable difference: the shield is no longer an active return conductor.

4.1 Susceptibility prediction using Ztd for a shielded pair The induced voltage Vi appearing in the shield (see Figure 5) due to the loop current is not directly seen as a differential voltage across the wire pair. Two situations may arise: a) General case If the link is a true balanced one, using differential drivers / receivers and wire pairs, we can start from the voltage Vi appearing inside the shield due to the loop induced current Ish (see Equation 3).

Each wire 1 and 2 is exposed to the same voltage Vi, such as if the symmetry was perfect, the difference Vi(1) – Vi(2) would be null. Since there is a certain percentage of unbalance in the wires resistances, capacitance to shield and leakage inductance vs the shield, the differential voltage will be : Vdm = Vi . X% . R L / (Rs + R L) where X% is the unbalance percentage of the pair. Depending on the quality of the balanced link, X may range anywhere from 1 to 10 percent, with typical (default) value being 5 percent, for high speed data links.

Thus, replacing Vi by its expression for a coaxial cable configuration, we get: Vdm = [Zt (Ω/m). l (m). I sh] . X% (R L/ (Rs + R L)) (7) We can therefore define a Differential Transfer Impedance Ztd that will include the shield Zt times the pair unbalance, augmented eventually by the shielded connector Ztc and its own unbalance ( the contacts balance vs the metallic connector shell is not perfect either and can deteriorate the whole link symmetry). This new parameter Ztd will allow a single pass calculation of Vdm, from a given sheath current. b) Case of unbalanced links using a STP. If the associated Transmitter // Receiver circuits are of the unbalanced type (single-ended), without Bal.to. Unbal. conversion devices, one wire of the pair will be tied to the 0V reference at both ends and the whole STP behaves as a pseudo-coaxial link. The only small advantage being that the return wire dc resistance is paralleling the cable shield, or that the Electronic Reference ( 0V) could be eventually floated from chassis, yet the shield being chassis-grounded.

Example 3 A high speed differential link is using a STP, with following parameters : LVDS Receiver: differential detection threshold: 100mV STP: 0.80m long, good quality braided shield, pair unbalance ratio: 5% interferencetechnology.com

Figure 5. STP equivalent circuit for susceptibility to field coupling and its mode conversion inside the shield.

System EMC specifications require a Bulk Cable Injection (BCI) test: 200mA rms, 30MHz – 200MHz What will be the differential voltage seen at the receiving end?

Solution Calculations are carried at 100MHz, which is about the worst case frequency region for 0.80m cable length.

1) Zt for a single braid @ 100MHz (Figure 2): 1Ω /m Corresponding Ztd for 5% unbalance : 5.10 -2 Ω /m Vdm for 0.80m cable ( Equ.7) : Vdm = 0.80 . 1 Ω /m.

5.10 -2 x 200mA = 8 mVrms Since fast digital circuits (receivers, comparators) tend to respond to the peak value of modulated RF, the actual EMI voltage will be: Vdm = 8.√2 = 11 mV, augmented eventually by a modulation coefficient.

Thus, based on shield coupling alone, the received voltage is 20dB below the LVDS detection threshold 2) The STP is terminated by plastic RJ45 plugs, with the shield grounded both ends via 12.5mm ( 0.5’’) pigtails.

What is the new value of Vdm? The total self-inductance for two pigtails ( typ. value 1nH/mm) is:

Lp = 2 x 12.5 x 1nH = 25nH Corresponding parasitic impedance added in series to Zt, at 100MHz:

Zp = Lω = 16Ω New value of Vdm, with the contribution of 2 pigtails (taking into account a same 5% unbal. as for the pair)

Vdm = [(0.80 . 1 Ω /m . 5.10-2) + 16 . 5.10-2] x 200mA

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= 170 mVrms, or 235 mVpk This is more than twice (6dB) the LVDS detection threshold. The pigtails have deteriorated the transfer impedance of a fairly good braid by more than 20 times ( 26 dB). Metallic connectors insuring an integral shield grounding are necessary.

4.2 Application of Ztd to an EMI radiated emission case With true differential links using differential drivers / receivers and wire pairs, the current returning by the shield is only prorated to the percentage of asymmetry in the pair. If the transmission link is balanced with X percent tolerance, the unwanted share of current returning by the shield is, for the worst possible combination of tolerances, only X% of the total current.

In this case, Equation 4 becomes:

Vext = X% . Zt (Ω/m) x l (m) x

V0 / Z L (8) Thus, the radiated field is reduced by a factor equal to X percent, compared to a coaxial cable situation.

To the contrary, if the wire pair is interfacing circuits that are not balanced (e.g., the signal returns being grounded at both ends), a larger portion of the signal current will use the shield as a fortuitous return, like with case 4.1.b). This portion is difficult to predict. At worst, this unbalanced configuration cannot radiate more

Figure 6. STP equivalent circuit for radiated emission, reciprocal to susceptibility case of Figure 5.

than the coaxial case.

Example 4 Using the same high speed differential link as example 3, calculate the field radiated at 3m by the fundamental component of a 100MHz data stream, with following parameters: LVDS Driver , maximum differential output: 1000mV

100 Ω STP : 0.80m long, good quality copper braid shield unbalance ratio: 5% cable diameter= 0.5 cm height above ground = 75 cm Solution 100MHz fundamental voltage, using usual Fourier series formulas for 50% duty cycle:

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Eliminate Interference...

Figure 7. Measured results for good quality STP. The balance is better than -40dB up to 30MHz, the worst unbalance being – 30dB ( 3%) at 100MHz. (Courtesy of Alain Charoy, AEMC / France)

1000 mVolt x 2/ π = 640mV Differential current, assuming matched load at receiving end:

640mV / 100Ω = 6.4mA Corresponding shield external voltage, using Ztd (Ztd is taken from example 3 @ 100MHz):

Vext = Id . Ztd x lm = 6.4. 10 -3 (1 Ω /m . 5.10 -2 x 0.8m ) = 260. 10 -6 V Characteristic impedance Zc of the cable, 75cm above ground:

Zc = 60 Logn (4.h/d) = 60 Logn (4 x 75 /0.5) = 380Ω External current driven into the cable-to-ground loop by Vext:

Iext = V ext / Zc = 0.7.10 -6 A Loop area = 80 x 75 = 6000 cm2 Radiated field at 3m ( see Example 2)

E (µV/m) = [ 1.3 . Acm 2 . Iamp . F(MHz) 2 ] 1/D

E (µV/m) = 18 µV/m, or 25 dBµV/m This is about 22 dB below the FCC Class B limit.

If the shield grounding was made by the same pigtails as example 3, their deterioration of Ztd would raise the field to 380 µV/m ( 51.5 dBµV/m) exceeding the limit by 5 dB. V. Actual measurements results with good quality Ethernet STP Figure 5 shows an example of unbalance measurements on an Ethernet type STP. Such measurements require a rigorous instrumentation set-up to prevent parasitic effects from obscurinterferencetechnology.com

ing the results. For instance, the Balun transformer, converting the symetrical 100Ω outpout to the unbalanced 50Ω input of the Spectrum Analyzer, must have at least a balance 14 dB better than the best pair being evaluated. This would just grant a < 2dB uncertainty of the results.

References • [1]. Schelkunoff, S. Electromagnetic Theory of coaxial lines and cylindrical shells, Bell Syst. Technical Journal, 1934 • [2]. Mardiguian, M. Controlling Radiated Emissions by Design, 2nd Edition, Kluwer Academics, 2001

MICHEL MARDIGUIAN, IEEE Senior Member, graduated electrical engineer BSEE, MSEE, born in Paris, 1941. After military service in the French Air Force, worked for Dassault Aviation, 1965 to1968. Moved to the IBM R&D Lab. near Nice,France, working in the packaging of modems and digital PABXs. Mardiguian started his EMC career in 1974 as the local IBM EMC specialist, having close ties with his US counterparts at IBM/ Kingston,USA. From 1976 to 80, he was also the French delegate to the CISPR Working Grp on computer RFI, participating to what was to become CISPR 22, the root document for FCC 15-J and European EN 55022. In 1980, he joined Don White Consultants (later re-named ICT ) in Gainesville, Virginia, becoming Director of Training, then VP Engineering. He developed the market of EMC seminars, teaching himself more than 160 classes in the US and worldwide. n

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System Compatibility: An Essential Ingredient for Achieving Electromagnetic Compatibility and Power Quality for Lighting Control Systems Philip Keebler Kermit Phipps Frank Sharp EPRI Lighting Laboratory

Introduction or years, lighting systems have been operating as stand-alone loads without the use of sophisticated lighting controls for energy savings in all types of facilities—residential, commercial, and industrial. Utilities and end users viewed lighting controls in the past as, luxury, systems that were used only when mood or special effects lighting was needed. Although two industries—broadcast and theatrics— have relied on dimmable lighting and basic lighting control systems for years as a part of their stage and set lighting, systems were very simple and traditionally dimmed only incandescent lamps. Other types of light sources were either not dimmable or did not provide the color performance needed for television cameras or live audiences.

Today, however, the need to provide dimmable lighting systems in more types of customer spaces is different today. With the help of lighting designers and energy researchers, end users are finding more applications for dimmable light sources paired with more sophisticated lighting control systems. Dimming is no longer limited to incandescent and electronic fluorescent systems. Dimmable lighting device designs are finding more application in electronic

F

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high-intensity discharge (HID), induction, and LED devices and other advanced lighting systems. Lighting researchers are discovering more ways to optimize lighting levels in various spaces by incorporating the use of dimmable light sources and lighting control systems. Commercial facilities are probing deeper into new applications for dimmable light sources and lighting control systems in efforts to improve energy savings.

Some installations are even making better use of outdoor light as they strive to harvest as much daylight as possible to offset their energy usage for lighting systems. Utilities are experimenting with various dimmable light sources and various types of lighting control systems through EPRI demonstration and other projects while examining customer perceptions, how much energy savings can be achieved without interrupting the customers’ business, and verification of savings before rebates and incentives are issued.

The federal government and other supporters of green initiatives are putting pressure on building designers, utilities, and end users to improve energy savings in various types of facilities. Lighting is one of those load types where energy savings is very achievable, and if implemented correctly, can be employed without introducing lighting and power quality problems into customer facilities. With lighting representing as much as 23% of the grid load, with many customer spaces characteristic of over illuminated conditions, and, to utilize emc Test & design guide 2010

2011 IEEE International Symposium on Electromagnetic Compatibility

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power quality daylight to offset the need for electric lighting, there is much opportunity to reduce energy usage and demand with the use of dimmable light sources and lighting control systems.

Utilities and customers alike who do engage in using dimmable light sources and lighting control systems do so today with many reservations and concerns. They are aware of some problems that have occurred when pairing dimmable light sources with lighting control systems in common everyday electrical environments. Several of these problems resulted from compromised lighting device and controls performance caused by poor power quality (PQ) and poor electromagnetic compatibility (EMC).

Utilities and customers expect new systems to work well together and to function properly in their expected electrical environments regardless of facility type. Lighting control systems should function properly regardless of what other neighboring loads are used in a facility. When compatibility problems occur with lighting devices and/or control systems, even lighting problems can grossly affect the customer’s business operations regardless of which type of lighting device—fluorescent, HID, or LED— is used. Some problems are severe enough to cause facility shutdown until action can be taken to disable the lighting control system. These problems can result in lost downtime and re-installation costs that can add up to the thousands of dollars.

The complexity of these systems and the demand for complete functionality warrants the need for improving the compatibility between lighting devices and control systems and their electrical environments.

Utilities and end users must endure increased pressure to improve building performance and reduce lighting energy costs while controlling facility budgets.

This ar ticle seeks out to describe the importance of achieving compatibility between lighting devices and control systems and the electrical environment while 76

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understanding PQ and EMC barriers that typically occur with lighting devices and control systems. Past EPRI research in the area of system compatibility has been applied to many types of electronic lighting devices. The application of EPRI's system compatibility concept can be used for lighting control systems not only to document energy, emissions and immunit y performance, but to harden lighting controls systems and to continue hardening electronic lighting devices.

Compatibility Problems with Lighting Controls Regardless of the type of communication link used to communicate with controllable light sources, their networks spread out across a facility and penetrating the electrical and electromagnetic environment.

Lighting control systems may use various types of communication links in essentially all types of lighting devices—fluorescent, HID, and LED: • Hard-wired, low-voltage, 0 – 10 volt DC, analog control • Line-side, line-voltage control • Line-side, low-voltage, three-wire control • Wireless (e.g., Zigbee) • Line-side, power-line carrier control • Hard-wired, low-voltage, DALI (Digita l ly Addressable Lighting Interface) control.

Each method of communication requires dedicated electronic circuits inside the lighting device. Penetration of the communications circuit inside the lighting device further exposes the other electronics inside the lighting device to malfunction and upset. For example, when an electrical fast transient (EFT) is coupled into a lighting control circuit, this voltage anomaly is carried to the electronic inside the lighting device.

The electrical and electromagnetic environment can both interact with each of these communication systems to cause any of the following compatibility problems, all of which have been witnessed in the field by EPRI and various end users.

• I nability to turn light source on

when an ‘on’ command is sent • I nability to turn light source off when an ‘off’ command is sent • I nability to dim light source up (increase intensity) when a ‘dim up’ command is sent • Inability to dim light source down (decrease intensity) when a ‘dim down’ command is sent • Complete malfunction of lighting controller (light sources will not respond to any end-user initiated commands) • Unstable operation of light sources (flickering lamps, random turn ‘on’, random turn ‘off’, etc.)

• Complete failure of lighting controller The sources of electrical and electromagnetic disturbances that can affect lighting controls include many types of industry defined waveform disturbances and random waveform disturbances that extend from a few tens of hertz up to hundreds of megahertz. Such disturbances can be generated from a wide variety of end-use equipment and operation of electrical equipment inside a residential, commercial or industrial facility.

Although the number of disturbance sources is not as many in residential settings as in commercial and industrial settings, the types of equipment that can generate these disturbances in residential settings is increasing as end users acquire more non-linear electronic loads like high-definition televisions and electronically controlled appliances including those with adjustable speed drives (ASDs).

Example sources include the following • Transients generated by the switching ‘on’ and ‘off’ of large loads such as heat pumps, refrigerators, ovens, pumps, washers, dryers, etc., and even induction cooking appliances • Conducted noise generated on the power line by electronic loads including electronic lighting devices using electronic ballasts and by failing power supplies in computers, audio and video equipment, and in gaming equipment • Voltage notching generated by the operation of highly-inductive loads (appliances that contain ASDs and motors) emc Test & design guide 2010

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Figure 1. Example of lighting control system with multiple circuits.

Figure 2. Electrical and electromagnetic disturbances that can impinge upon a lighting controller.

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emc Test & design guide 2010

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A c h i e v i n g EMC, P o w e r Q u a l i t y f o r L i g h t i n g C o n t r o l S y s t e ms

Malfunction or Malfunction or Failure with Lighting Controls Electrical or Electromagnetic Disturbance

Potential Damage to Front End Circuitry

Potential Damage to Low-Voltage Input 1

Interruption

Complete System Shutdown

System Lockup

•

Sags

•

Swells

•

Overheating of Power Supply Component

•

Loss of System Settings

Dimming Malfunction

Sensor Malfunction

•

• •

•

Distortion

•

•

Notching

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

Transients & Surges 2

•

Electrical Noise

(Conducted Emissions)

•

•

Table 1. Cross-reference between electrical and electromagnetic disturbances and malfunctions or failures of lighting control systems.

Figure 1 illustrates the basic concept of the primary ports commonly used on a lighting controller and how they can act as entries for electrical and electromagnetic disturbances.

The line input port is a line-voltage power port usually rated at 120 volts AC but may also be rated at a universal voltage (e.g., 120 to 277 Vac) or higher AC line voltage (e.g., 230 Vac) in European applications. The dimming control ports (four shown in Figure 1, other controllers may have fewer or more of these ports) are low-voltage ports and usually rated for up to 10 volts DC. These ports deliver a very small power to the dimming control circuit of a dimmable lighting device. Most lighting controllers have two or more sensor ports which may be used to support one or a series of remote sensors located somewhere out in a facility at a considerable distance from the controller. In Figure 1, these are the photocell (daylight sensor) port and the occupancy sensor port. To operate these sensors, a separate DC supply voltage is required—usually 12, 15, or 24 volts DC. The communications port is also a low-voltage port, but for network signals where multiple conductors which can be Ethernet,

• Voltage distortion generated by increasing penetration levels of electronic appliances that inject harmonic currents into the customer wiring system • E lectrical noise on the branch circuits generated by radiated emissions from radio transmitters, wireless devices, etc.

• Transients (surges) generated by thunderstorms and lightning strikes and also transients picked up by automatic lawn sprinkler systems Moreover, with the use of lighting controllers there is another opportunity for control system upset caused by radiated transients and high-frequency radiated emissions that can also be coupled onto any one of the hard-wired communications links. The thousands of feet, or miles (in some cases), of control cable is exposed to electric fields generated by transients and emissions and may cause distortion or corruption of control signals. In almost all cases, these cables are either not shielded or contain the very minimum amount of cable shielding due to the added expense of shielded cables.

1 2

Dimming port, sensor port, or other low-voltage port Includes ring wave, combination wave, capacitor switching, and electrical fast transients (EFTs)

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K e e b l e r , P h i pps , S h a r p

Figure 3. MOV failure caused by thermal runaway and internal equipment fire in a lighting controller.

Figure 4. MOV failure caused by thermal runaway and internal equipment fire in another lighting controller.

RS-232, or RS-485 are used. The wireless port is one that is showing up more on lighting controllers. This port and the network port(s) may be of an open (e.g., Zigbee) or closed architecture.

and failures that may occur with lighting controls. Each one of these has occurred in the field as reported by utilities, various manufacturers and end users. Some of these may be resolved with a system reset and some require hardware replacement. Others may require a circuit enhancement in the lighting controller to improve the immunity of the system to a specific disturbance. Regardless, these present

Exposure to Electrical and Electromagnetic Disturbances A lighting controller installed in a facility, whether the facility is a residential, commercial, or industrial one, is subject to the same exposure to electrical and electromagnetic disturbances as any other piece of networked electronic equipment (e.g. a computer) which also uses control and signals ports and control cables. Figure 2 illustrates several scenarios where disturbances can impinge upon the hard-wired and wireless ports of any lighting controller used to control any lighting device—fluorescent, HID, or LED. Each port essentially has some susceptibility to these disturbances, and this susceptibility will, at some level and frequency, cause the lighting controller to malfunction, be upset, or be damaged. The question is “How susceptible are lighting controllers to the electrical and electromagnetic disturbances that commonly occur in the customer’s electrical (facility) environment?” The only way to definitively determine their susceptibility is to test them in a controlled laboratory environment capable of generating industry standardized, random, and field documented disturbances.

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Cross-Referencing Disturbances and Failures with Lighting Control Systems Because of the nature of lighting control systems and the electrical and electromagnetic disturbances that occur in environments where multi-port systems must live, there is significant opportunity to improve their performance. Performance improvements are based on which disturbances impact which part of a lighting control system and the severity of the malfunction or upset. Obviously, any disturbance that causes permanent damage must be resolved without delay. Table 1 lists various types of malfunctions interferencetechnology.com

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problems to the end user that will likely interrupt the nature of their business and function of the lighting control system.

In some situations, the interruption will present safety issues to the facility or its occupants as well.

Discussions with manufacturers of lighting controls and end users who have installed them in the past several years have revealed that the nature of compatibility problems as listed in Table 1. Compatibility problems are indeed occurring and increasing with some communication methods.

The good news is that the performance of lighting control systems can be improved with the application of EPRI’s System Compatibility concept. The increase in compatibility problems among lighting control systems can be attributed to four causes: 1) the increased complexity of lighting control systems (i.e., more use of electronic microcircuits and more use of low-voltage ports for network, control and signal functions, 2) the increased complexity of the electrical and electromagnetic environments where systems are installed, 3) the increased frequency of use (i.e., end users are using them more often in applications where lighting control is needed or required to meet certain specific energy savings goals) of lighting control systems, and 4) the increased development of new electronic lighting devices and their increased use.

One area where failures have increased is in the protection of the AC power port against voltage surges. In visually inspecting MOV failures in lighting controls, thermal runaway has been increasingly observed. Thermal runaway may occur if an MOV with too low of a maximum allowable voltage is applied in lighting control equipment in efforts to provide protection against voltage surges. In such a case, an MOV’s exposure to a long-term overvoltage may be higher than the MOV’s maximum allowable voltage, and thermal runaway of the MOV may occur without blowing the line fuse. Figures 4 and 5 show two examples of MOVs in lighting controllers, which failed as a result of thermal runaway.

In both examples, the MOV ignited and a significant part of the MOV material was burned by the fire caused by its own thermal runaway. The fire from the MOV damaged other nearby electronic components and the enclosure for the lighting controller. If investigators discover this type of MOV failure surrounded by other burned insulation and electronic components, then thermal runaway can be suspected. These susceptibilities, or weak links in the design of these lighting controllers, can be identified through compatibility analysis and testing at the EPRI Lighting Laboratory.

this. . . . Lightning strikes near a telemarketing facility. The uninterruptible power supplies connected to the computer systems switch on, but some of the computers lock up, disrupting data processing and vaporizing data. The light from the overhead dimmable fluorescent lighting system fades as about one-third of the fixtures go out. Or perhaps you don’t have to imagine if you use magnetic HID ballasts with metal halide lamps and have been left in the dark for 15 to 20 minutes before the lamps cool down enough to restrike.

Imagine this type of problem when your lights are connected to a lighting controller. The lighting controller is in full command of the lights, but the lights cannot be turned back on because the controller already says they are on.

Every year, problems with electricity and electrical equipment cost U.S. companies billions of dollars in scrap material, down time, damaged data, and delayed orders. Every year, electric utilities produce and deliver almost two billion cycles of electricity. If just a few of those cycles are disturbed, computers in commercial offices may crash, industrial equipment may shut down, and entire processes may grind to a halt. Moreover, equipment in one facility may cause other equipment in the same facility or in a neighboring facility to malfunction, even when the quality of delivered power is perfect. With lighting controls, which are embedded within a facility’s electrical system, these problems become even more compounded. Each wired port on a lighting controller is a “door” for an electrical or electromagnetic disturbance to enter the controller. With facilities becoming more cluttered with electronic equipment, the frequency of occurrence for disturbances, their disturbance levels (both low and high frequency) are increasing. As buildings become more intelligent, more compatibility problems will surface and render equipment inoperable.

Applying Power Quality and Compatibility to Lighting Controls Power quality is the concept of powering and grounding electronic equipment in a manner that is suitable to the operation of that equipment as defined by the IEEE Standard 1100, The Emerald Book. (Early EPRI research in the area of system compatibility provided many contributions to this publication.) Power quality is a concept that was developed to study and improve the quality of electric power as it is generated, transmitted, and distributed to utility customers and consumers by electrical and electronic equipment.

Manufacturers and consumers often misapply the definition of power quality. Without even a basic understanding of power quality, they often think of quality power as power that contains absolutely no imperfections. Mistakenly, they apply the same thinking to lighting controllers as well as electronic lighting devices. Similarly, an electrical engineer unfamiliar with the power quality concept may think of quality power with a ‘perfect sine wave’ with no irregular waveshapes or distortion whatsoever and a data string as a perfect stream of zeroes and ones. Both of these are incorrect perceptions of power quality as the input power to lighting controllers and the data they must deliver and receive contain artifacts

System Compatibility and Power Quality What is a power quality problem? Imagine this. . . . The fluorescent lights connected to a lighting controller in a manufacturing facility blink, indicating that the voltage has briefly dipped. A split second later, the high-intensity discharge (HID) lights drop out, adjustable-speed drives that control process motors trip, and scrap material gathers on the floor of the now dimly lit manufacturing facility. A few minutes later, the indoor LED lighting devices begin to oscillate, causing the illumination to rise and fall slowly. Or 82

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Figure 5. A rising data pulse (going from zero to one) corrupted with conducted noise.

resulting from the occurrence of electrical and electromagnetic disturbances in customer facilities.

Figure 5 illustrates a rising data pulse captured on a port of a lighting controller that receives a command from a daylighting sensor. This pulse is supposed to be a digital zero traversing to a digital one (e.g., 0 volts traversing to 5 volts) in an attempt to activate dimming of a bank of dimmable lighting fixtures connected to one of the dimming ports of a lighting controller. The pulse contains high-frequency conducted noise. This noise has entered the control cable that runs from the controller to the daylight sensor with timing and amplitude characteristics limits set by the manufacturer. The cable was shielded, but the shielding material failed. The shield did not reduce the noise current in the shield that resulted from the in flux of a high-frequency radiated electric field present in the building. The electric field was generated by a set of input power cables running from an electrical panel to the input of a set of adjustable speed drives.

Because these emissions are associated with the electrical branch circuit inside a building. The operation of the ASDs (i.e., a non-linear load), created the problem on the branch circuit. This is considered to be a system compatibility problem. The quality of the voltage on this circuit is corrupted by the presence of these high-frequency emissions.

Because the lighting controller is susceptible to these emissions, the controller is deemed to have a compatibility problem with its common interferencetechnology.com

everyday electrical environment. One might ask, are these emissions really common in a commercial or industrial electrical environment where the compatibility problem occurred? All ASDs produce some conducted emissions on their input circuitry which travel out of the ASD up the branch circuit. The emissions levels among ASDs do vary with ASD manufacturer and model as well as the impedance and length of the branch circuit and some other variables. These emissions were being coupled into the daylight sensor control cable as the cable was run in parallel and too close to the branch circuit powering the ASD. One could remove the problematic lighting controller and replace it with one that had the exact same design (i.e., same input power requirements, same types of lighting control channels with the same daylighting control functions) and this problem may never have occurred.

The immunity of the daylight sensor input when used with a specific control cable and daylight sensor will vary among lighting controller. However, in this case the problematic lighting controller has an immunity low enough to allow this problem to occur while other controllers had a higher immunity to these emissions at these frequencies.

The lighting controller was rendered inoperable as a result of this compatibility problem and was removed from the facility. This indicates a couple of major points for concern: 1) the shielding of the control cable was insufficient to protect the data signal inside the cable from the radiated electric field and 2) the port of the lighting controller could not filter out this noise in the

data signal and caused the controller to lockup.

In order to better understand power quality and system compatibility and how it can be applied to the characterization of end-use equipment like lighting controls, EPRI has developed a detailed concept called system compatibility which can be applied to any electronic device including lighting controls. A series of system compatibility tests can be applied to a lighting controller to determine its energy, emissions, and immunity performance for each power and signal port and the product as a whole.

An EPRI test procedure exists which allows each type of electrical and electromagnetic disturbance to be applied to the proper ports of a lighting control.

The low-frequency disturbances are derived from definitions for each type of voltage variation and disturbance that occurs on the power system and inside customer facilities. These definitions, which are now standardized and part of an IEEE standard 1159-1995 (R2001), IEEE Recommended Practice for Monitoring Electric Power Quality, were in part developed through actual power quality studies conducted at EPRI on various power systems across the United States in the last 15 to 20 years. Through having developed a thorough understanding of power quality, power system engineers and system compatibility engineers (engineers who study the compatibility between the power system and end-use electrical and electronic equipment) have been able to determine how equipment responds to each type of variation and disturbance.

What is System Compatibility?

When equipment and appliances get along in the same electrical environment, they are said to be in a state of system compatibility. System compatibility is defined as the ability of a device, equipment or system, generally a load, to function satisfactorily with respect to its power-supply electrical environment without introducing intolerable electrical disturbances to anything in that environinterference technologyâ&#x20AC;&#x192;

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tion, the controller may or may not initiate the request properly. Moreover, the controller (or a separate monitoring device) may or may not be able to verify that the request was actually carried out. A situation where a request called for the dimming of certain lights may actually have occurred, but verification of that request indicated otherwise.

The converse problem may also occur.

Regardless, compatibility problems with lighting controllers may leave the utility (and the customer) in a state of unknown when it comes to load reduction and energy savings.

Figure 6. The design process with integrated system compatibility testing.

ment. However, in today’s complex and diverse electrical environment, achieving system compatibility is often a steep challenge for any product designer, especially for multiport systems like lighting controllers where compatibility must be applied to each port. For example, modern industrial processes rely on sophisticated electronics for precise and continuous process control, and malfunction and upset of these electronics can jeopardize process reliability. Industrial plants that rely on process reliability also rely on quality lighting control systems. When these plants apply demand response, utilities will be relying on reliable communication and operation of lighting control systems to shave load when required to ensure power system stability. Commercial facilities are characteristic of the same types of disturbances and operation of disturbance-generating loads like ASDs more commonly 84

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used in heating, air-conditioning, and ventilation systems. An increasing number of lighting controllers rely on feedback from daylighting sensors spread throughout a facility to determine what appropriate levels of light are needed in task areas where sensors (and windows) are located.

There is more to the quality of a lighting system than measuring the photometrics of the light. A quality lighting system includes the following, some of which are directly influenced by a lighting controller. These general performance requirements are not only important to lighting controllers but are also important to demand response activities. Demand response requests will utilize lighting controllers to initiate commands to make adjustments in lighting loads by turning dimmable lighting devices ‘on’ or ‘off’ or change dimming levels.

If disruption to a lighting controller occurs in a demand response applica

Photometry Compatibility can also impact the photometrics of a lighting system.

In lighting control applications, it is important that a dimmable lighting device response as intended to a lighting control command. A compatibility problem may cause a lighting control system to render one of the following problems to a dimmable lighting device.

• P roviding an unstable arc (discharge) inside an HID lamp at some dimming level because the wrong dimming level was reached • Providing a sable DC current for an LED fixture (a driver function) • Providing an incorrect amount of foot-candles targeted toward an area where the light is needed • Providing an incorrect color of light where light of a different color is needed • M aking an inappropriate adjustment (too low or too high) light levels based on how much ambient light enters a room or space Safety, Compatibility, and Power Quality Safety must be the first priority in any facility regardless of the business activity. Reliable and compatible lighting systems play a vital role in maintaining safety. Lighting devices and lighting control systems which are not compatible with the electrical environment will increase the risk of an accident occurring. Aside from increased efficiency, one of the primary benefits of using electronics in lighting emc Test & design guide 2010

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Figure 7. Compatibility concept applied to lighting controller, demand response system, and overall system.

devices is to enhance safety-related performance. However, if the electronic ballast (or driver) is not compatible with the electrical environment, then safety-related performance will likely be compromised. Listed below are some examples of why lighting is critical to safety.

• Keeping the lights on when they are needed • M inimizing the number of lamp drop outs • Maintaining as much lumen output for the life of the lamp as possible – called lumen depreciation – to avoid light levels that are too low before lamps reach the end of their expected life • A void i ng l a mp f l icker a s t he load inside and outside a facility changes – f lickering lamps may cause rotating machinery to appear 'standing still' Compatibility, Reliability and Economics Electronic lighting devices and lightinterferencetechnology.com

ing control systems require a capital investment. To reap the return on investment (ROI), projected costs must be maintained within their estimate to avoid stretching out the pay back period. Pay back periods for lighting upgrades usually run from about one year to as long as three to four years depending on a variety of factors. Utilization of lighting controls typically shortens the pay back period. Listed below are examples of some cost-related expectations: • Maintaining efficacy (efficiency) for the expected life of the ballast and lamp or the driver and LED • Achieving enough lamp and ballast or LED and driver reliability to achieve a return on the investment that the customer has made in purchasing and installing the modern lighting system • Ensuring that the lighting control system of an electronic ballast or electronic driver remains fully operational over the life of the ballast/ driver so that lighting load can be

adjusted according to customer needs or the utility’s desire to reduce peak load in future demand response applications Each of the above categories involves the use of a lighting control. Considering a few examples, the first two categories in the above list are centered around the lamp and the fixture. The next two bullets are related to the performance of the lamp-ballast or LED-driver system.

This performance also depends on how the lamp-ballast or LED-driver system responds to variations or disturbances in the AC line voltage powering the lighting system.

EPRI research indicates that LEDdriver systems combined with lighting controls may be more susceptible to common everyday electrical and electromagnetic disturbances than lampballast systems combined with the same controls. When the customer makes an investment to purchase and install a modern lighting system such as one that uses high-frequency HID or LEDs, that customer expects the system to operate interference technology

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power quality reliably. Reliable operation should last for at least a minimum of the warranty period. The warranty period offered by the lamp, ballast and fixture manufacturer will likely be different. The lighting specifier, retrofitter, and/or installer can help one understand the nature and design of warranties and their periods.

A severe electrical event, such as a near lightning strike, high voltage distortion, or a larger than expected number of sags may occur during the warranty period.

Manufacturers may not honor the warranty if extreme events occur. Powerline monitoring of the lighting branch circuit, a facility power quality audit, and/or a forensic analysis on a failed ballast (or driver) or lighting controller by EPRI may reveal the cause of an early failure. If the facility environment reaches a high ambient temperature, the lamp and ballast (or LEDs and driver) life may be shortened possibly causing premature failure.

Why Apply System Compatibility to Lighting Systems?

Traditionally, lighting systems from the days of Thomas Edison were of the incandescent type. No energy conversion device was needed between the power system and the lamp, and no lighting controls were used. This does not mean that disturbances in the power system did not affect incandescent lamps. This simply means that the incandescent lamp is under direct influence of disturbances that occur on the power system. Compatibility tests conducted on incandescent lamps have shown that the reliability of lamp filaments are affected by disturbances such as voltage sags, voltage swells, and voltage surges. With respect to the end user, a change in illumination is usually noticeable with these disturbances until the lamp fails to produce light when the filament is severed. With lighting control systems, failures and malfunctions in lamps are also possible and can actually be initiated by malfunctions in lighting controllers.

Early f luorescent-based lighting systems were developed by leading manufacturers soon became popular lighting products for end users of all types. These systems through the use 86â&#x20AC;&#x192;

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of a magnetic ballast were connected to a fluorescent lamp. The purpose of a ballast is to produce enough energy to ignite a lamp and then control its illumination through either voltage or current control.

In magnetic fluorescent lighting systems, the magnetic ballast is a simple core-and-coil type of device with no sophisticated electronic components for controlling lamp performance. These ballasts also respond to various types of steady-state and transient power-line disturbances. With vary little voltage regulation built into a magnetic ballast, the ballast will allow an increase in illumination with an overvoltage or a voltage swell and a decrease in illumination with a voltage sag. However, the core and coil of a magnetic ballast system have the distinct advantage of having a more-thanacceptable immunity to voltage surges.

Although this type of immunity helps to increase ballast reliability, end users often complain about issues other than ballast failures such as noticeable variations in light fluctuations. These fluctuations in light output are called lamp flicker. All types of lamps and lamp-ballast systems have their own characteristic response to various types of voltage fluctuationsâ&#x20AC;&#x201D;the type of line-side disturbance that causes lamp flicker.

Lamps and lamp-ballast systems may act as amplifiers of voltage fluctuations or they may act as attenuators to fluctuations. Each component of the lamp-ballast system plays a different role in determining the extent to which the lamp-ballast system acts as an amplifier or attenuator of fluctuations.

When acting as an amplifier, a small fluctuation incident on the AC input of a lamp-ballast system, for example, will result in a large change in light output.

The same is true for lighting controllersâ&#x20AC;&#x201D;disturbances initiated at the line input may find their way through the lighting controller and into the signal that controls the light output of electronic ballasts.

With respect to end users, each human eye also has a distinct frequency response to lamp flicker. Some people can notice a lamp f lickering when others cannot. Some will indicate

that what may be defined by some as a mild lamp flicker will actually cause severe headaches, thus preventing users from functioning in a work environment. This is because their perception to lamp flicker varies from person to person. Lamp flicker studies have been conducted on many types of incandescent and fluorescent lamps and ballasts with the results varying among lamp and ballast models as expected. As more lighting systems become electronic, lamp flicker studies will continue to gain more attention, especially for systems operating at higher lamp wattages such as HID lamps where a small amount of flicker in a fluorescent lamp may not be very noticeable as compared to that same amount of flicker in an HID lamp that may be more noticeable.

W hile the human perceptionrelated performance issues in lighting systems can gain much attention from utility customers, professionals in the lighting industry traditionally focus on lamp and ballast performance and reliability. These professional groups include architects, lighting specifiers, facility electrical designers, lighting engineers, and lamp and ballast designers. Each of these groups strives to provide acceptable lighting systems for their customers that meet their expectations in terms of lamp and ballast performance and reliability. Each strive to 1) provide lighting systems that maintain acceptable light output for the majority of the life of the lighting system and 2) provide lighting systems that function at an acceptable level for at least the term of the product warranty.

Manufacturers of electronic fluorescent ballasts learned about performance and reliability the hard way.

Many of them did not understand the whole-system performance: how to design a high-frequency inverter type of power supply, populate a printed circuit board with components rated for an elevated operating temperature, solder them to the board, place that board inside a metal can, pour hot potting material over the circuit, and install it into a lighting fixture.

Many lessons regarding circuit design, emc Test & design guide 2010

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component reliability, soldering, specifications, and potting were learned.

With some knowledge about ballast reliability and the warranty term, many manufacturers did not have enough data to reasonably design and specify their warranty programs. Both manufacturers and end users experienced significant financial losses from poor lamp and ballast reliability.

Many have asked how system compatibility testing could have prevented much of these financial losses. At the time when the first electronic fluorescent ballasts were being designed, component manufacturers were also not familiar with applying their devices in ballasts. Component engineering combined with a temperature-based compatibility study might have helped reduce the number of failures cause by the overheating of electronic components. Compatibility testing would not have had much of an effect on manufacturing defects including soldering.

However, during many of the forensic studies that were conducted on failed electronic fluorescent ballasts, it was found that disturbances which would not normally affect a well-designed electronic ballast would have a much more negative effect on the performance and reliability of a ballast with design problems. Disturbances such as voltage transients and voltage sags were found to cause premature failure of ballast circuits and the component lead-to-solder joint junction. Compatibility testing on such samples prior to production would have resulted in the identification of ballast reliability issues prior to the installation of thousands of ballasts that eventually failed when powered in a normal electrical environment.

For these reasons, manufacturers and end users of electronic ballasts, whether they produce or use fluorescent, HID lamp-ballast, or LED systems, must have a keen awareness of the compatibility of these systems with the power system. Many are integrating compatibility testing into their ballast design processes with the goal of identifying compatibility problems long before the start of production.

EPRI has worked with dozens of ballast interferencetechnology.com

manufacturers and applied the compatibility concept to their products.

Manufacturers of LED drivers and LED lighting systems are just beginning to recognize the importance of EPRI compatibility testing for their products. If lighting controls are to be a key part of a facility’s lighting system to help reduce energy usage, then the same needs to happen for all lighting controllers.

Figure 6 illustrates the design process with integrated system compatibility testing. This process served as the guideline during the development and testing of the many electronic ballast products. Lighting control designers can learn to apply the compatibility concept (See Figure 7) just as easy as ballast manufacturers have done. The process is basically the same, but the results will be different and just as valuable.

How Compatibility Enables Lighting Control to be Demand Responsive With basic lighting controllers having been developed several years ago, some with fairly mature designs, many controllers will continue to be used as individual systems separate from demand response (DR) systems.

However, while the compatibility of a DR system is just as important as the compatibility of a lighting control system, the overall compatibility of a combined DR-lighting control system will be critical for facilities that begin to rely on them. Figure 7 illustrates this concept. Interestingly enough, many of the lessons to be learned regarding compatibility for lighting controllers will also be applicable to DR systems.

Conclusion: System Compatibility is Important for Lighting Controls As stated earlier, lighting controls are becoming a key part of a facility’s operating system. Prior to the use of lighting control, lights in a facility were just turned ‘on’ at the beginning of a day and turned ‘off’ at the end of a day.

Now, facilities are having to become more intelligent and vary light levels according to occupant usage, space

purpose, and ambient light levels. If facilities are to engage in energy savings using lighting controls, then the controls that they use must be hardened to the point where facility manages and occupants can expect them to function as desired in all types of electrical environments and building operating conditions. The electrical environment of the facility, including emissions and disturbances generated by the lighting devices themselves, must not impact the operation of lighting control systems.

Lighting controllers will need to function during thunderstorms, during electrical disturbances initiated by the public, and during electrical disturbances initiated by the utility. Lighting control designers may even want to consider integrating intelligence into the control that alerts the end user when an adverse condition exists such as the presence of a high level of electrical noise on one of the communication or port channels. Resolving a compatibility problem with a lighting controller before it shuts the building lighting system down would be very valuable.

EPRI maintains expertise in solving compatibility problems with lighting controls. Expertise in this area can be used to further understand compatibility problems with lighting devices and control systems. End users simply cannot work in the dark, or under poor lighting conditions and in some conditions the failure of a lighting control system would present safety problems requiring the building to be evacuated.

EPRI is positioned to further the maturity of lighting devices and controls through its research and testing in its Lighting Laboratory.

Philip F. Keebler manages the Lighting and Electromagnetic Compatibility (EMC) Group at EPRI where EMC site surveys are conducted, end-use devices are tested for EMC, EMC audits are conducted and EMI solutions are identified.

Kermit O. Phipps is a NARTE Certified engineer and conducts tests and evaluations of equipment performance in accordance with the EPRI System Compatibility Test Protocols for EPRI. Frank Sharp is a Senior Project Engineer / Scientist at EPRI in Knoxville, Tenn. n interference technology

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Everybody Talks Quality, We Think Seeing Is Believing.

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The way we see it, quality is about results. If a product can’t cut it in the real world, you won’t get the answers you need. And we won’t get the loyal customers we need.

So here’s to companies and customers who still respect – and demand – quality.

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