RE: Scope of EN 61000-4-8 (Power Frequency Magnetic Testing)
This can be a little confusing. In a previous post: Magnetic fields tend to build up low value EMF sources in series with loops and have extremely low impedances. When any electronic circuit contains loops, at a low impedance level, this circuit will almost certainly be affected by the test's field. You may think of low impedance wheathstone bridges, If we are talking about the susceptibility of a given (VICTIM) circuit to external magnetic fields, then circuits with HIGH impedance loads are most susceptible. See Ott 's Noise Reduction Techniques page 40, Paul's Intro. to EMC, page 522. If the focus is on the SOURCE (or aggressor) circuit, then it is reasonable to say that low impedance circuits with their associated, (and assumed) large di/dt create crosstalk problems dominated by inductive coupling. But from the discussion I assumed that the focus was on the VICTIM circuit during immunity testing, where an Mdi/dt voltage is induced into a victim circuit. In this case circuits with LARGE load impedances are most susceptible. For circuits that are large compared to the noise wavelength, it may be better to talk about far end and near end coupling, rather than simply low impedance or high impedance loops. All of these discussions presume that the victim circuit uses voltage signaling to convey information. If the discussion is about circuits that use current signaling (a 4-20 mA loop,or a transimpedance amplifier), then it may be better to talk about the effect of source or load impedance of the victim circuit on the induced noise current level in the victim circuit. Regards Lee Hill Silent Solutions LLC EMC RF Consulting and Training lh...@silent-solutions.com www.silent-solutions.com -Original Message- From: Gert Gremmen : ce-test, qualified testing [mailto:g.grem...@cetest.nl] Sent: Wednesday, March 27, 2002 2:32 AM To: Jim Ericson; emcpost Subject: RE: Scope of EN 61000-4-8 (Power Frequency Magnetic Testing) Hi Chet, There are many other standard electronic equipment that qualify them for these tests; possibly not in the phase of compliance seeking, but at least when looking for simple quality. Magnetic fields tend to build up low value EMF sources in series with loops and have extremely low impedances. When any electronic circuit contains loops, at a low impedance level, this circuit will almost certainly be affected by the test's field. You may think of low impedance wheathstone bridges, audio output amplifiers; virtual ground sink input in opamps and many other applications. Also, in high end, low level or high dynamic range equipment , the EMF value induced by the field may directly cause performance issues . For this to happen one does not need a low impedanc e path. Finally any equipment containing air coils, or any other non closed magnetic field loop coil may pick up EMF voltages from this test. If these EMF source that buil up in the coil cause a performance problem is entirely dependent of the design, of course. It's for this reason that for professional audio systems EN 55103 the application of a magnetic field source test is prescribed for the full audio frequency range. Looking just at VDU and Hall sensors is a bit restricted, although i definitely agree that for power frequency issues they are the vast majority. Regards, Gert Gremmen Ing. ce-test, qualified testing ce-marking more http://www.cetest.nl --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: PCB Design Books
I like John's recommendations Of all the books he lists my favorites are Paul, Ott, and Johnson. I have not finished Hall, Hall, and McCall yet. Early on Mardiguian wrote about some good troubleshooting ideas and techniques that Scott Roleson had also published (I'm not sure who was first). John, I found Bennett's book a little tough to teach from and not very accessible for those that do not eat, sleep, and drink EMC. But I am willing to take another look. Some other books that I find people recommending are Keenan's Digital Design for Interference Specification 2nd Edition ISBN 0-945049-02-1 and Williams's EMC For Product Designers 2nd Edition ISB N0-75062466-3 I don't think they are as good as the first three, but they do have some good explanations of a few topics. I have found several other books on the topic that are either a 1) rehash of electromagnetic theory without pertinent applications, 2) vague in their recommendations, or worst yet 3) so empty of mathematical justification that some ideas seem to be made up. One way to judge the quality of a book and the knowledge of the author on the topic of PCBs and EMC is to carefully look at how the author talks about inductance and grounding. These topics are treated very well in Paul's and Johnson's book in particular. Other books on the topic do the usually bad job, talking about the inductance of pieces of etch or wire, or present a dogmatic approach to something like multipoint grounding or single point grounding, often without any illustration or practical examples with real numbers and math. Best Regards Lee Lee Hill Founding Partner Silent Solutions LLC EMC Consulting and Training 10 Northern Blvd., Suite 1 Northwood Executive Park Amherst, NH 03031 (603) 578-1842 x203 (V) (603) 578-1843 (F) lh...@silent-solutions.com www.silent-solutions.com In a message dated 10/31/2001 12:23:23 AM Eastern Standard Time, jhow...@emcguru.com writes: Subj: Re: PCB Design Books Date: 10/31/2001 12:23:23 AM Eastern Standard Time From:jhow...@emcguru.com (John Howard) Sender:owner-emc-p...@majordomo.ieee.org Reply-to:jhow...@emcguru.com (John Howard) To:marti...@appliedbiosystems.com CC:emc-p...@majordomo.ieee.org Hi Joe, and All I would suggest several excellent texts which will contribute to the subject. I use these in the EMC courses which I teach on PCB design. Control and Measurement of Unintentional Electromagnetic Radiation W. Scott Bennett --- John Wiley Sons, New York, 1997 High-Speed Digital Design H. W. Johnson M. Graham --- PTR Prentice Hall, Englewood Cliffs, NJ 1993 High-Speed Digital System Design S. H. Hall, G. W. Hall, J. A. McCall --- John Wiley Sons, NY 2000 Controlling Radiated Emissions By Design. Second Edition Michel Mardiguian --- Kluwer Academic Publishers, Boston, 2001 Noise Reduction Techniques in Electronic Systems, Second Edition Henry W. Ott --- John Wiley Sons, NY, 1988 Introduction to Electromagnetic Compatibility Clayton R. Paul --- John Wiley Sons, NY, 1992 Best Regards John marti...@appliedbiosystems.com wrote: To all, What book would you recommend for designing printed circuit boards for EMI suppression? Why? Regards Joe Martin --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old
Re: EMI trouble shoot inquiry
Hello Wm: Troubleshooting an EMI problem by telephone or email is usually a very tall order. The best that could probably happen is for someone to point you in the right direction. 1) I agree with Ken, a clue lies in the generator frequency 2) Does the problem occur only at the station where the signal generator is used? If so, this gives a big clue to the nature of the coupling 3) If by ferrite tiles you mean broadband absorbers, these are usually intended for absorption of incident RF at frequencies above 30 MHz. Their reflection coefficient is poor by design, so they wouldn't help nearly as much as a localized conductive shield or high mu material (if these turned out to be appropriate solutions) 4) I bet the stationery read/write heads drive a high Z input amplifier/IC. That is the most likely place for the system to be disturbed. Chances are you have either capacitive coupling into the amplifier, or inductive coupling in to the head/amp interconnect. Were your copper shields tied to the low side of the amplifier? 5) If the problem is occurring at the RFID read frequency (530 kHz), and some absorption is the key, then steel is not necessary, thick copper (~ 0.5mm) will give 40 dB attenuation at this frequency. But it may easier to either reduce the read circuit loop area, and/or provide a local capacitve (copper/tin/any good conductor) shield at the receive amp/IC. You need schematics and pictures to solve this problem effectively and quickly. Lee Hill Founding Partner Silent Solutions LLC EMC Consulting and Training 10 Northern Blvd., Suite 1 Northwood Executive Park Amherst, NH 03031 (603) 578-1842 x203 (V) (603) 578-1843 (F) lh...@silent-solutions.com www.silent-solutions.com In a message dated 10/15/2001 2:57:03 PM Eastern Daylight Time, wmf...@aol.com writes: Subj: EMI trouble shoot inquiry Date: 10/15/2001 2:57:03 PM Eastern Daylight Time From:wmf...@aol.com Sender:owner-emc-p...@majordomo.ieee.org Reply-to:wmf...@aol.com To:emc-p...@ieee.org CC:jim.gi...@hedus.com Group: I attach an RF interference inquiry from a customer; I have no 'smarts' where RF ID is concerned, so I turn to this august body... ==paste==We have an OMRON RFID data transfer system operating within the same room as 12 RF generators (bombarders). The transmission frequency for the RFID system is 530 kHz and the transmission frequency for the bombarders is 400 kHz. The RFID system works through an antenna embedded in a pallet and a stationary read/write head. The bombarders are positioned on a platform overhead. The normal sequence is for a pallet containing a bulb to move via conveyor to a read/write station where information is taken from and added to the pallet. The pallet is conveyed through several different processes, being read/written on roughly 8 occasions. One of the processes contains an RF generator. We are experiencing problems with the RFID system when the RF generators are on. The read/write system operates properly when the RF generators are off. We have determined that the RF generators are creating an interference that does not allow the RFID to operate properly. Initially, w! e built copper shields in the area of some of the RFID stationary heads. This did not seem to help. We also placed EMI suppressors on the RFID cables(near the read heads). This also was not helpful. I have spoken to a company that suggested the use of Ferrite tiles to absorb the interfering waves. The problem with these tiles is that they are very brittle and difficult to use for shields. The concept sounds good but I don't have much flexibility in where I can place the shields. I am currently trying to use ferrite magnets attached to the copper guards. Any help/suggestions you could give me would be greatly appreciated. ===end paste== Thanks for any suggestions; reply as you see fit. WmFlanigan --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. --- Headers Return-Path: owner-emc-p...@majordomo.ieee.org Received: from rly-xe02.mx.aol.com (rly-xe02.mail.aol.com [172.20.105.194])
HP 8591EM EMC Analzyer for Sale
HP/Agilent EMC Analyzer Model 8591EM, 9 kHz - 1.8 GHz (1.9 GHz actual), $9900 asking price. The -EM version includes quasi-peak detection, narrow resolution bandwidth filters, AM/FM demodulation speaker, with built-in EMC automation options and external plug-in EMC personality card, and precision frequency reference.. Always transported in protective case and option 040 protective front cover (latter is included, along with manuals), this unit is in good working and cosmetic condition. Calibrated one year ago. We are selling this unit because it is being replaced by a new machine with coverage to 26.5 GHz. Please note that this posting is permitted under the listserver guidelines at http://www.ewh.ieee.org/soc/emcs/pstc/: The listserver is provided as a service by the IEEE, whose policies prohibit anything that might be construed as conflict of interest. Exceptions: New or used equipment wanted, or used equipment offered for sale (not offered by the manufacturer) Thank you. Lee Hill Founding Partner Silent Solutions LLC EMC Consulting and Training 10 Northern Blvd., Suite 1 Northwood Executive Park Amherst, NH 03031 (603) 578-1842 x203 (V) (603) 578-1843 (F) lh...@silent-solutions.com www.silent-solutions.com
Re: EMSCAN (was TV nostalgia/EMI sniffer goggle)
We have found the limited resolution of EMCscan to limit (!) its usefulness -
it can't pinpoint IC level problems, for example. Although marketed for
emissions work, it is not usually the best tool if you are hunting down
radiated emissions, since its response to (large) differential-mode currents
will tend to swamp out its response to (small) common-mode currents. The
color plots are fun to look and occasionally can spark some intuition.
As Kyle said, the practical requirement of laying a PCB flat against it makes
it tough to use for much of our work.
Lee Hill
Silent Solutions LLC
EMC Consulting Training
www.silent-solutions.com
In a message dated 8/8/2001 11:26:55 AM Eastern Daylight Time,
george.stu...@watchguard.com writes:
From:george.stu...@watchguard.com (George Stults)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to:george.stu...@watchguard.com (George Stults)
To:keh...@lsil.com ('Ehler, Kyle'), ken.ja...@emccompliance.com ('Ken
Javor'), emc-p...@majordomo.ieee.org
I also looked at EMSCAN about 2 years ago. I seem to recall that it was
limited to a little over 1GHz on the top end at that time. We didn’t buy
it, because we had harmonics above 1 GHz.
-George
-Original Message-
From: Ehler, Kyle [mailto:keh...@lsil.com]
Sent: Tuesday, August 07, 2001 12:24 PM
To: 'Ken Javor'; emc-p...@majordomo.ieee.org
Subject: RE: EMSCAN (was TV nostalgia/EMI sniffer goggle)
I mini-evaluated an EMSCAN about 4 years ago. Cute tool!
At the time, this little gem utilized a planar array of 1,024
microantennae, coupled to an RF processor and pc.
The radiation display is a user-variable-interpolation color map (spectral
or spatial), but a bit imprecise in X-Y location, and forget about the Z
plane. You could see a circuit trace acting as an emitter, but you have to
be diligent in comparing the pwb layout with the schematic and the tool's
radiation profile report. It was also a bit slow. That might have changed
since then.
Here's a link: A
HREF=http://www.emscan.com/product/prodline.html;http://www.emscan.com/product/prodline.html/A
I could not sell our pcb design engineers on the tool -not even for use as
a prescanner. Now our mechanical folks are having a dickens of a time
containing 2Gbps fibre channel harmonics after the pcb design is done.
Thanks for the job security. boneheads
The biggest problem with this weapon was the absolute need for close
proximity and repeatable indexing. This severely affects the accuracy and
repeatability of the results, making before/after comparisons questionable..
For many of us, placing an operating pwb on a planar surface for scanning
presents a major challenge.
I dont know about you, but we have a backplane that the pwb plugs into,
then of course there is cabling, power supplies and cooling to worry about..
Not to mention the CRU canisters for each module. Then it needs to be
functional.
I witnessed differences in emission profile that were highly sensitive to
operating modes of the firmware loops and application software. It is
extremely difficult if not impossible to do an accurate comparison of a
bare board to an assembled and completely functioning EUT. So you are
forced to scan a bare board rather than a fully configured and functioning
system. For our purposes (debugging the EMI containment) this was of no
practicality. Back to sniffer loops and horns..
On the other hand, one of the proper ways to design for compliance is to
design for containment of the emissions at the [board level] source. This
is where the practicality of the EMSCAN comes into play. I found the
tool's virtue for scanning the solder side of the board (close proximity)
excellent, but for the component side (which is where most of the radiation
sources and fixes would occur) the proximity was poor, grossly affecting
the location and precision of the readings.
btw I dont work for, or have any connection with, EMSCAN.
kyle
-Original Message-
From: Ken Javor [A
HREF=mailto:ken.ja...@emccompliance.com;mailto:ken..ja...@emccompliance.com/A]
Sent: Monday, August 06, 2001 5:58 PM
To: John Woodgate; emc-p...@majordomo.ieee.org
Subject: Re: TV nostalgia
You could use an array of very short dipoles or small loops and gain in
resolution by giving up efficiency, meaning that the viewer would have to be
near the source. Although I have no detailed knowledge of it, I expect this
is the principle behind the devices upon which you lay an operating PCB and
the device maps hot spots. But clearly you will never get optical or IR
viewer resolutions.
--
From: John Woodgate j...@jmwa.demon.co.uk
To: emc-p...@majordomo.ieee.org
Subject: Re: TV nostalgia
Date: Mon, Aug 6, 2001, 12:28 PM
95fbd8b0830ed511b7720002a51363f1319...@exw-ks.ks.lsil.com, Ehler, Kyle
keh...@lsil.com inimitably wrote:
