Re: TC77b Rewrite of 61000-4-2 and 61000-4-4
HI Eric and the group, The main difference in the ESD test is in how the waveform is specified. The waveform is not being changed, just a better specification and calibration procedure for the simulator. Some ESD simulators may need little or no change while others will need a redesign. Some changes to testing procedure will make testing easier to pass because the original intent in the test was not explicit enough and resulted in overtesting. In any event a new document is sometime in the future as far as being in place in the EU requirements. Since document changes can still take place, it would not be wise to change any decisions now, even if you had the draft document. But, to keep things in perspective, the price of an ESD simulator a few years from now, when the standard MAY be in place, will be small compared to your cost if a perfectly good product fails because the simulator can pass calibration, yet significantly overstress your equipment compared to a different brand of simulator. I think everyone's cost will in fact be lower overall. There has been a tendency lately for chip manufacturers to claim their chips pass IEC 61000-4-2 in their advertising. This test was never intended for chips and has no methodology to do such a test. The wording in the document will make it plain that it is a misapplication of 61000-4-2 to test chips with it. Another problem resolved. Doug On Tuesday, Nov 12, 2002, at 09:54 US/Pacific, hellflo...@aol.com wrote: I want to make sure everyone is aware of the tidbit of information Doug offered on the GR-78 thread. Readers may want to reconsider capital equipment purchases of related test equipment, and certainly the impact on manufacturers of sustained product lines (typically industrial) over the next three or four years. In a message dated 11/11/02 11:08:35 PM, d...@emcesd.com writes: Interesting coincidence, I am in Chandler, AZ USA for a meeting of IEC TC77b (high frequency immunity) to rewrite the ESD (61000-4-2) and the EFT (-4) specs. The new test will be quite different than the existing one with the main benefit being more repeatable results. Comment - I applaud efforts to improve a test, however the broad impact of these standards may not help the EMC community gain favor with corporate management. Best Regards, Eric Lifsey e.lif...@ieee.org http://ewh.ieee.org/r6/utah/ --- 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 ___ _Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o | Email: d...@dsmith.org \ _ /]\ _ / Web: http://www.dsmith.org --- 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: GR-78 Circuit pack ESD test.
Hi Gary, Can you give us more details? If I remember correctly from my Bell Lab days, the circuit pack ESD test I remember was useless as it assumed boards were always held by the edges and zapped on a predetermined grid. If the waveform is slower than IEC 61000-4-2 (801-2 was replaced by this) the test is out of date and probably does not correlate to whether the board will survive under real conditions. I would only do this test for contract requirements (your case?). Interesting coincidence, I am in Chandler, AZ USA for a meeting of IEC TC77b (high frequency immunity) to rewrite the ESD (61000-4-2) and the EFT (-4) specs. The new test will be quite different than the existing one with the main benefit being more repeatable results. Doug On Monday, Nov 11, 2002, at 15:43 US/Pacific, Gary McInturff wrote: Anybody know what equipment provides the waveform described above? Its much slower than the IEC801 waveform. I tried Keytek and they don't have it. Other suggestions to perform the test - just use the IEC waveform? Gary --- 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 ___ _Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o | Email: d...@dsmith.org \ _ /]\ _ / Web: http://www.dsmith.org --- 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
pwb coupling to surroundings (continued)
Hi All, I have posted at http://emcesd.com the latest Technical Tidbit (picture link at bottom of page). In April and May, the Technical Tidbit articles discussed the coupling between a circuit board and a nearby metal plane. This month, Printed Wiring Board Coupling to a Nearby Metal Plane, Part 3: System Measurements carries the discussion of board coupling to nearby objects further with measurements on a board in a system enclosure. Results are dramatic and show that a circuit board is strongly affected by nearby metal structures. Data and pictures for the article were contributed by Neven Pischl of Broadcom. If you have a topic you would like to see covered in a Technical Tidbit that fits with the general topics of the website, let me know. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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
Kirchoff and Faraday voltage measurements
Hi All, Well, I have been writing again. This month my article is on voltage measurements. Voltage measurements can give misleading results with some measurements yielding a result that appears nowhere in the circuit of interest! This month's Technical Tidbit at http://emcesd.com is titled Kirchoff and Faraday Voltage Measurements - Don't Confuse Them. The article discusses two types of voltage measurements and why a measurement may give a result that is quite different than what is happening in the circuit. The link to the article is the measurement picture at the bottom of the main page. Also new on the website is a paper titled A Method of Accurately Measuring Shielding Effectiveness of Materials in Electronic Products at the bottom of the Technical Information and Downloads section. This is a white paper I wrote for one of my clients on measuring shielding effectiveness of materials that are close to the source (where plane wave measurements are not valid) such as in a cell phone or other small hand held device. For those of you who missed the IEEE EMC Symposium, I will be posting pictures from the Symposium in a few weeks. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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
active probe issues
Hi All, Most of us use active probes because we believe they have a high input impedance. However this is not usually the case in the upper octave of their stated frequency range. My Technical Tidbit article for August, 2002 (http://emcesd.com) presents measured data on a popular active probe typical of most on the market. You may be surprised at the result. I also give an example of a good active probe that has reasonable input impedance and response over its stated frequency range in real measurement situations. Its instruction manual also gives good equivalent circuits and other data necessary to use an active probe properly. It is one of the best probe instruction manuals I have seen relative to the sheer amount of information given. (I have no connection to or financial interest in the probe I use for the example, it just happens to be one of the best I have seen.) Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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
EMC test equipment - Cheap!
Hi All, Occasionally, test equipment designed for one use has another use quite distinct from the intended one, but in another field. Such equipment is often very inexpensive and yields useful results. In the July Technical Tidbit at http://www.dsmith.org (or http://emcesd.com), an example is given of an inexpensive piece of test equipment (about US$110) normally used by Amateur Radio Operators that can be used in noise, EMC, and SI design debugging. Several links are given, including one for a ~US$400 instrument that can make complex impedance and other transmission line measurements. On a different note, a few weeks ago I taught my high frequency design, measurement, and debugging course at Oxford University. Oxford is a great place!! Looking forward to going back. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: IEC 61000-4-2 ESD 61000-4-5 Surge lower levels
Not to mention the vastly different current risetimes. Low voltage discharges actually have higher di/dt values than high voltage ones (and therefore higher interference potential). Doug don_borow...@selinc.com wrote: Let me add a bit on the air discharge side. You will want to do the lower voltage discharge tests because the path the discharge takes may change with voltage. I have seen several instances where connectors (sub-min D types, if I remember correctly) were mounted on metal panels. At higher voltages, the path between the ESD gun and the grounded shell of the connector would break down first. At lower voltages, the connector pins could be approached without breakdown to the shell, and the discharge would occur to the connector pins. Don Borowski Schweitzer Engineering Labs Pullman, WA Pommerenke, David davi...@ece.umr.edu on 06/10/2002 06:36:46 AM Please respond to Pommerenke, David davi...@ece.umr.edu To: Neil Helsby nei...@solid-state-logic.com, emc-p...@majordomo.ieee.org cc: kro...@yahoo.com (bcc: Don Borowski/SEL) Subject: RE: IEC 61000-4-2 ESD 61000-4-5 Surge lower levels Dear Group, For most EUTs there is no need to do lower level testing in contact mode ESD. The time is better spend (meaning a better test results uncertainty is achieved) if the number of discharges is increased at the highest test level (hundreds is a good number). Although it is possible that a system fails at e.g., 2 kV contact mode (e.g., incomplete reset) and passes at 4 kV contact mode (full self-recovering quick reset) the likelyhood of that happening is not that large to require it in a standard. For air discharge lower level testing is needed, as the risetime is often much lower at lower voltages. Of course, if no discharge occurs, no further testing at even lower levels makes sense. I do know that what I am saying violates the present IEC 61000-4-2 standard. ut it reflects the coming version of IEC 61000-4-2. The standard does not intend to protect agains every possible ESD failure. I would like to receive your input, as I am one of the US-representatives in IEC TC77b WG-9 (ESD). David Pommerenke -Original Message- From: Neil Helsby [mailto:nei...@solid-state-logic.com] Sent: Monday, June 10, 2002 4:56 AM To: emc-p...@majordomo.ieee.org Cc: kro...@yahoo.com Subject: Re: IEC 61000-4-2 ESD 61000-4-5 Surge lower levels I think there are two points here. 1) If you believe that in the environment in which it will be used, your product may be subject to levels in excess of that defined in the standard, you must test to that higher level. 2) Yes, failures can occur at mid range levels. We have just recently experienced this problem with ESD. Below about 3.5 kV and above about 4.5 kV the product worked fine. But at 4 kV we experienced a failure mode. If we had only tested at 8 kV we would have missed the problem. I also had a problem some years ago with mains voltage dips to 0V. Having a test set that enabled the period to be varied in ms increments, I discovered a problem affecting a voltage regulator. When the mains dip was between about 16 ms and 35 ms, the regulator went into a bistable mode switching on then off at each pulse. Outside these periods, it worked satisfactorily, eventually losing output when the period was extended. The problem with investigating these types of failure is determining the size of step between measurements. Too short a step and you will be testing forever, too long and you could miss a narrow band of problem. Regards, Neil Helsby ** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com ** --- 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
Mutual inductance as a troubleshooting tool
Hi All, Mutual inductance can be a powerful debugging tool for problem circuits. It can also be either a friend or foe in the designs themselves. This month's Technical Tidbit at http://www.dsmith.org relates direct measurement of Ldi/dt voltage drop with Mdi/dt of the same voltage. Often direct measurement of a voltage drop is not possible. This article shows that Ldi/dt and Mdi/dt measurements can be equivalent. Yet another use for a probe made out of a paperclip! Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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
immunity of a pwb as a function of grounding
Hi All, I have been busy again setting up experiments and taking data on a circuit board that indicates a design rule for ESD that I have heard from many sources does not work. I knew this was the case, but thought some data was in order. This month, the Technical Tidbit at http://emcesd.com (or alternately http://www.dsmith.org) investigates the effect of board connections to a metal plane on its response to ESD. Scroll down to the bottom of the index page to link to the article. This article builds on the results of the April Technical Tidbit article where an oscillator was used as the excitation of a board over a metal plane. A circuit board from a disk drive was mounted near a metal plane and measurements of currents in connections to the plane were taken when the plane was excited by an ESD event. The results are dramatic and a major design rule about grounding circuit boards for immunity is shown to be ineffective. This article shows in a different way how strong the coupling between a board and a nearby metal plane is. At first I tried to use a small surface current probe for the measurement, but a null experiment showed that it was too sensitive to electric fields so I used a shielded square magnetic loop to make the measurement. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: A very nice game
Robert, You do not have to open the attachment on this one at all if you have IE! Just preview or open the message. During virus outbreaks, like this one, I use a great webmail reader mail2web.com to preview my mail before downloading it. Doug Robert Wilson wrote: In spite of the attachment having been removed by the system, it was pretty darned obvious what this must have been. It always amazes me that people are foolish (stupid?) enough to open attachments to obviously suspicious emails like this one, that are from people they don't know, and subjects that make no sense. Bob Wilson TIR Systems Ltd. Vancouver. -Original Message- From: Bill Ellingford [mailto:bill.ellingf...@motion-media.com] Sent: April 24, 2002 4:37 AM To: 'jmw'; emc-p...@ieee.org Subject: RE: A very nice game Importance: High URGENT Please be aware that the above E-mail to the EMC group contained a virus. Fortunately our system removed it from the message. Bill Ellingford -Original Message- From: jmw [mailto:j...@jmwa.demon.co.uk] Sent: 24 April 2002 22:59 To: emc-p...@ieee.org Subject: A very nice game -- Virus Warning Message (on gemini2) setup.exe is removed from here because it contains a virus. - * --- 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 --- 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 -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: A very nice game
Hi Chris and the Gang, It was probably a particularly nasty one called W32/Klez.h@MM which I have received through other channels several times lately. It is bad enough that if you actually get infected (McAfee will prevent this if your DAT files are reasonably new) you have to go into DOS and follow steps outlined my McAfee to get rid of it as it disables virus scanners. It appears to exploit an incorrect MIME header which causes IE to do some nasty things to your computer automatically by just opening or previewing the message. MAC's and PC's with Netscape Mail do not seem to be infected. I opened the letter in Netscape Messenger and did not get either a warning message or an infection. A URL on McAfee about this is: http://vil.mcafee.com/dispVirus.asp?virus_k=99455 One way to help avoid this type of thing is not to open email larger than a few tens (a long text message) of kB without knowing before who sent it and why. Long messages can harbor viruses. Doug Chris Chileshe wrote: Bill, Do we know which virus it was? Regards -Original Message- From: Bill Ellingford [SMTP:bill.ellingf...@motion-media.com] Sent: Wednesday, April 24, 2002 12:37 PM To: 'jmw'; emc-p...@ieee.org Subject:RE: A very nice game Importance: High URGENT Please be aware that the above E-mail to the EMC group contained a virus. Fortunately our system removed it from the message. Bill Ellingford -Original Message- From: jmw [mailto:j...@jmwa.demon.co.uk] Sent: 24 April 2002 22:59 To: emc-p...@ieee.org Subject: A very nice game -- Virus Warning Message (on gemini2) setup.exe is removed from here because it contains a virus. - * --- 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 This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk --- 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 -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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:
Re: Suitable CDN for IEC61000-4-6 ethernet 10/100
Hi All, Just a word of caution about test equipment used to measure EUT performance, such as a LAN-analyzer or similar equipment that counts errors. My experience has been that some of this equipment is itself very susceptible to EMI. In a recent case, I had to move a bit-error tester to the other side of the lab on the end of a fiber in order for it not to register errors while testing the EUT. It was so sensitive that low levels of ESD in the room (not applied to the EUT), that did not affect the EUT itself, caused the test equipment to register many false positive error counts. On a similar point, on that same job, I found the lab scope (a modern 5 GSa/sec unit) was itself susceptible. One of my techniques to measure EMI induced noise on a board would not work because the scope displayed more noise with a closed 50 Ohm termination, instead of my measurement apparatus, on its input BNC than the noise I was trying to measure in the first place. Doug Gary McInturff wrote: Yup, when we do immunity testing - we see the occassional crc error or the ilk, but I've never seen a problem with the link. We use an Ixia box to cram data down the lines. There are probably many other traffic generators that will work just fine but none of them are pocket change. Gary -Original Message- From: Pommerenke, David [mailto:davi...@ece.umr.edu] Sent: Friday, April 19, 2002 8:28 AM To: Chris Maxwell; emc-p...@majordomo.ieee.org Subject: RE: Suitable CDN for IEC61000-4-6 ethernet 10/100 What you should take into account is the failure criteria for 61000-4-6 as seen by the EU: No degradation beyond manufactueres specification. Depending on the EUT just a few additional bit-errors at any of the tested frequencies may be a fail. It may not be sufficient to just look at loss of link. In many cases, a low level LAN-analyzer is needed to do this test. Otherwise, effects of lessere severeness than loosing link will not be detected, although they may be a fail of the test. David Pommerenke -Original Message- From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Friday, April 19, 2002 7:53 AM To: emc-p...@majordomo.ieee.org Subject: RE: Suitable CDN for IEC61000-4-6 ethernet 10/100 From David Sterner's message: Most people use the EM clamp. We test to EN50130-4 alarm system limits: 10V, pulsed and AM modulated. The test is trivial because of the inherent immunity of Ethernet; be sure you understand the EUT and AE port partitioning algorithms. What! The test is trivial because of the inherent immunity of Ethernet. The last product that I took through the lab couldn't even take 3V...heck, the Ethernet cable couldn't even take 3V being put on some of the other cables in the chassis. Now, before everybody sends me design tips for Ethernet immunity...save your breath... the chassis was a purchased computer. It was EMC tested (with only a dummy ethernet cable and no traffic, mind you). And I have no design control of the ethernet circuit. We ended up using shielded Ethernet cables and invoking the 3meter rule. The point that I'm trying to make is...I'm glad that this test is trivial for your products. Obviously, you have a good design there(Where were you when we were looking for a compliant mainframe to use with our system?) But this type of immunity performance cannot be attributed to all Ethernet ports in general or to the Ethernet protocol in general. Best regards, Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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 --- 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:
Capacitive coupling to cables
Hi All, I have posted the latest article on my website at http://emcesd.com: Cable Effects Pt 3: Capacitive Pickup by Cables in a System Last month the Technical Tidbit on http://emcesd.com explored inductive coupling to cables. The article for March discusses capacitive coupling to cables in a system and how to distinguish it from inductive coupling by measurement technique. Also shown is how little coupling capacitance is needed to keep you from shipping a system. Enjoy! (I enjoy writing these articles and hope most engineers enjoy reading them!) Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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...@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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
coupling to cables
Hi All, Well a new month and my typing fingers get restless. After an afternoon doing experiments, I have come up with some information on coupling from devices to cables in a system. Local fields emanating from devices in a system that would normally not be a problem can induce currents in nearby cables that can cause significant problems. This month's Technical Tidbit on http://www.dsmith.org details measurements on the results of inductive coupling into a cable. The measurements show a dramatic result in terms of the amplitude of the induced current. Also shown: the relative phase between two current probe outputs (as seen on a scope or on a spectrum analyzer using a combiner) can be used to confirm the inductive mode of coupling (as opposed to the capacitive mode of coupling). Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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...@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: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
[SI-LIST] job postings
Hi All, I have a page on my website where I post both positions available and persons looking for positions. I do this as a service (no charge for the posting). Three new positions have been added in the last few days, one this evening from Maryland. The direct URL of the page is: http://emcesd.com/jobs/jobpost.htm This page contains only job posts, no technical stuff or ads. If you want to post a position feel free to send me an mail and will put it up for you. If others on this list have similar job posting pages, perhaps they can also share them also. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- -- To unsubscribe from si-list: si-list-requ...@freelists.org with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-requ...@freelists.org with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu
cable discharge measurements
Hi All, I have seen some postings recently on the technical lists on cable discharge so I decided to do a few measurements using a simple test setup. Cable discharge happens when a cable becomes statically charged and then is connected to equipment. This can happen by dragging a cable on the floor or just holding in in your hand as you plug it into equipment. Lately there have been reports of damage from this effect to computer interface circuits. This month's Technical Tidbit on http://www.dsmith.org presents the results of measurements on a simplified form of cable discharge. The data shows high peak currents and high di/dt values as well. The test setup is simple to make and is useful for other measurements as well. A similar test setup was used for the Technical Tidbit on measuring inductor performance at: http://www.dsmith.org/tt050100.htm Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Elusive Glitch - Part 3
The Elusive Glitch - Part 3 This month on http://www.dsmith.org, the Technical Tidbit is the final Part 3 of the Elusive Glitch story. The first two articles in October and November talked about how ESD and other impulsive events can disrupt measurements on digital circuits. Also covered were techniques for determining when such disruption is occurring. Part 3 of the Elusive Glitch for December shows how fields from impulsive events can be accurately measured. This is not a technique most of us will use in the lab, but standards committees are using such methods to write new standards that will show up in our design requirements in the future. -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: Impedance Stabilization Network
Hi All, I suspect that Fischer Custom Communications should have them. Their website is: http://www.fischercc.com/ Doug Heffken, Jan wrote: Does anybody know of a source of ISN's as required for Telecom Port conducted emissions in CISPR 22? Jan Heffken Compliance Test Engineer Applied Innovation Inc. j...@aiinet.com --- 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. -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
more glitches
The Elusive Glitch - Part 2 Hi All, This month, I describe in my Technical Tidbit article (www.dsmith.org) a way to accurately pinpoint the source of a waveform glitch. It takes last month's article one step further than just determining if a glitch is likely coming from an external source instead of the circuit being measured. The technique uses an extra channel(s) of a scope to determine if the glitch is real or a result of external EMI and is reminiscent of the amateur radio transmitter hunts I participated in as a teenager (except in the time domain this time). Knowing this information can save a lot of engineering time in the lab and has become more important as circuits and measurement instruments have increased in speed. Equipment can now be affected by EMI sources that have not been a problem until the last few years. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: EFT Failures..Help!
Hi Alex and the group, Often, one is very lucky to be able to fix such a problem while at the lab. Time there is best spent collecting data on the failure. Things like the actual failure voltage, cable positioning effects, and the such are important data that will make your device easier to troubleshoot in the lab. There are lots of troubleshooting techniques described on my website (www.dsmith.org). For instance, trigger a scope from the EFT generator and then use a magnetic loop (insulated paperclip will do) to trace the EFT current flow through your product. Once the exact path is known, often the solution is obvious. Because the EFT signal is (sort of) continuous and easy to trigger on, I have found EFT problems very easy to fix. Forget using any commercial scope probes though, they are useless in an EFT environment, too senstive to stray pickup. For products with metal enclosures, the balanced coaxial probe described on my website can measure signal voltages in the presense of ESD or EFT in equipment. I am working on a new balanced probe design that will work even better for this use as well as on signals past 1 GHz, but my first prototypes will not be ready for a few months, too late for your problem. Doug Alex McNeil wrote: Hi Guys, I am at an EMC test centre today and tomorrow. Unfortunately, my product failed EFT testing on the AC power port at 1KV. This is for various combinations of Line, Neutral and Earth (L, N, E, LN, LE, NE and LNE) My product is Class II, no Earth. It is supplied by an external power supply. This supplies SELV to my product. The power supply manufacturer has stated that his power supply meets EN61000-4-4 for 2KV and has emailed me this report to verify this. Has anyone got a quick solution to my problem so that I can implement here at the EMC test house? Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.com --- 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. -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
wasted engineering effort
Hi All, It seems we spend quite a bit of time tracking down glitches on logic signals. Once a glitch has been found that appears to be causing a system to hang-up, reset, or otherwise not perform as expected..Now what? All may not be as it appears and if not, a great deal of engineering time can be wasted. The Technical Tidbit article this month at www.dsmith.org discusses glitches that appear in scope waveforms that can lead an engineer or technician on a wild goose chase away from potential real problems. The article is located near the bottom of the home page. Just click on the scope screen picture to read the article. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: ESD Immunity Testing
Hi John and the group, Some commercial simulators have a lot of multi-gigahertz ringing on their waveforms but still pass the crude waveform specification. You might be seeing this energy depending on your brand of simulator. There has been discussion in the committee on ground lead positioning. Possibly David Pommerenke can fill you in on the latest as I had to miss the committee meeting a few weeks ago in Quebec City due to my heavy involvement with the EOS/ESD Symposium in Portland, OR. Doug John Woodgate wrote: I read in !emc-pstc that Douglas C. Smith d...@emcesd.com wrote (in 200109281718.naa27...@swiftsure.cnchost.com) about 'ESD Immunity Testing', on Fri, 28 Sep 2001: Also, the waveform specification in IEC61000-4-2 is currently so poor that commercial guns having vastly different outputs can pass the test yet affect equipment differently. Would you care to comment on the apparently uncontrolled energy path back from the EUT to the 'ground' of the gun? We seem to have these picosecond rise-time currents flowing through long bits of wire - maybe expensive and arcane wire, but ... -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Eat mink and be dreary! --- 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. -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: ESD Immunity Testing
Hi Richard and the group, There are lots of problems with existing standards that would take to long to describe here. In general, the limits of instrumention and time constraints I think are the main reason for existing shortcomings. IEC 61000-4-2 is being rewritten and the current draft looks much better than the old standard, but may not reach acceptance in its present form. I think Michael Hopkins of KeyTek has a better sense of what is going on with that. An observation on statistics: Low voltage events are much more common as you said. The problem comes in that low voltage events are more likely to cause upset with many forms of equipment as the di/dt is much higher than for high voltage events. The current IEC waveform is much too slow to model a low voltage event and so would not be a good predictor of field performance. As equipment goes to faster speeds (higher bandwidth) this effect becomes more important. I have observed equipment upset many times from ESD events with current risetimes on the order of tens of picoseconds! Compare that to the 700 ps to 1 ns risetime of the IEC waveform and you see what I mean. Also, the waveform specification in IEC61000-4-2 is currently so poor that commercial guns having vastly different outputs can pass the test yet affect equipment differently. This was less of a problem several years ago when equipment was slower. The standard was based upon instrumentation that was available at the time it was written. Adding all this to what you have said, it is not hard to see why ESD testing results often seem like magic. A quote I saw sometime ago (forgot source) said: Any process with a sufficiently high number of incontrolled parameters seems like magic. Doug wo...@sensormatic.com wrote: Since my last posting on trying to find an ESD expert, I have had to become that expert. After reading the ANSI ESD standard and its references, it is clear that ESD experts are mostly in agreement on how to correctly perform ESD immunity testing. It is also clear test methods in the EN/IEC specifications do not follow that advice. ESD testing is a statistical process, so the test methods and the analysis of the results must be based upon statistics. There are three basic causes. 1) The distribution of ESD events in the operating environment has a non-uniform distribution where the number of expected events per hour is inversely proportional to approximately the square of the voltage. This implies in testing that the number of applied zaps in testing and their levels should also follow this distribution. 2) Digital devices are state machines and some states may be less immune to ESD than other states. This implies that each state should be tested. However, most digital devices have a huge number of states and they change very quickly; therefore, the only way to ensure that even most of the states have been evaluated is to apply a very large number of zap. 3) There may be a probability distribution for the locations on the machine where an ESD discharge is likely to occur. That is, it is not always equally likely that a person or an object will come in contact with any given point on any given surface. Statistics can be used to determine the voltage levels that should be applied and the quantity required at each level in order to provide a specified confidence level that a machine will have no more than a specified number of errors per unit time. However, the number of zaps required is very high, usually in the order of one to ten thousand. The drawback, of course, it that the testing can be time consuming. However, applying in the order of one hundred zaps to a machine according to the EN/IEC specifications will provide such a very, very low confidence level that one cannot reasonably predict the expected error rate in the field. Worst, the results are not repeatable since some states may be tested during one test session and others may be tested during another session. The only predictable case where this might not occur would be with a machine with an ESD robustness level for all states that are far above the actual test levels. So here is my question to those of you involved in the EN/IEC standards - why have these statistical test processes not been acknowledged in the standards? Richard Woods --- 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
paper posted
Hi All, I have posted the paper I just delivered at the EOS/ESD Symposium in Portland, OR titled The EMI/ESD Environment of Large Server Installations. If you work a server company, supplier to such, or in an organization that maintains servers, you may be interested in this paper. It is posted in pdf format on my site at: http://www.dsmith.org The link is in the blue tint area near the top of the page where news items are located and in the list of papers further down the page. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
FET probe caution
Hi All, Did you know that a common accessory for FET probes can, in some cases, cause a significant error in the measurement? My September Technical Tidbit at: http://www.dsmith.org describes the problem. The accessory in question is a probe tip with a small ground spring or pin on a hinge and uses a small ferrite core to improve probe response. Its use can make the FET probe ten times more sensitive to logic noise on the board and other EMI that you are not trying to measure. Such a sensitivity can cause one to see a glitch that is not there on a logic signal, a real time burner in the development lab or troubleshooting environment. The article presents scope data to show the magnitude of the problem which affects several brands of FET probes. The Technical Tidbit area is at the bottom of the index page. -- In addition, I have posted pictures to the website from Montreal and the IEEE EMC Symposium that was held there a few weeks ago. The link to the pictures is just above the Technical Tidbit area at the bottom of the index page. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: STP vs FTP Ethernet cables
Hi Paolo, I worked for a few years in the part of Bell Labs that was involved with networking cable systems several years ago. I am suspicious of foil shielded cables as it is difficult to properly terminate the foil shield (360 degrees). I have had a foil shield crack and split if the cable is flexed very much. On a related topic, a good UTP (unshielded twisted pair) system can have lower emissions and higher immunity than most shielded systems. The interface design is not hard to do to make this happen. I have seen cases where the presense of the shield causes immunity problems because a large noise current lands on the chassis of the data equipment. It there are slits and holes in the chassis (back of a PC?) problems result. Take a peek at the paper: http://www.dsmith.org/pdf/roma94.pdf which I authored several years ago and presented at the EMC Roma conference. In that paper a couple of commercial STP systems were compared with a good UTP system at a test lab in Switzerland. The UTP system won hands down on both emissions and immunity! The presense of a shield, by itself, does not guarantee good performance. I seem to remember also that the shielded systems had higher losses for signal transmission than UTP which resulted in shorter permissable cable lengths. Paolo, we can go offline if you want to discuss more details. Either call or email me. Doug Paolo Roncone wrote: Hi all, anybody out there can explain the difference between FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links. In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP (herebelow in copied and pasted from the standard - page 28): In a vendor's catalog, I found a definition of FTP as 1.4.249 shielded twisted-pair (STP)cable: An electrically conducting cable,comprising one or more ele- ments,each of which is individually shielded.There may be an o erall shield,in which case the cable is referred to as shielded twisted-pair cable with an o erall shield (from ISO/IEC 11801:1995).Speci .cally for IEEE 802.3 100BASE-TX,150 . balanced inside cable with performance characteristics speci .ed to 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 11801:1995).In addition to the requirements speci .ed in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 provide additional perfor- mance requirements for 100BASE-T operation o er STP. The reason of my inquiry is that we bought samples of STP and FTP cat.5 cables for 10bT ethernet applications from different vendors and to our surprise we discovered that both STP and FTP types have an overall (external) shield made of aluminum foil, but no shields on individual wires or wire couples (as per 802.3 definition above). Any inputs, suggestions etc. would be appreciated. Paolo --- Paolo Roncone EMC Compliance Engineer - Cisco Photonics Italy via Philips 12 - Monza (MI) 20052 mailto:pronc...@cisco.com phone: +39 039209 1538 fax: +39 039209 2036 -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
Re: ESD Testing
Richard, With today's faster circuits low voltage evernts may be more likely a problem than high voltage ones. Low voltage air discharges have much higher di/dt (and therefore interference potential) than high voltage events. A device that passes 15kV may easily fail at 1 kV because the di/di at 1 kV is MUCH higher if it uses logic with sub-nanosecond risetimes. Doug wo...@sensormatic.com wrote: Do any of you perform ESD testing at or above 15 kV to improve product robustness? I have the following questions. o What types of products o What type of user environment o What is the rational for testing above 15 kV o What test equipment is used above 15 kV o What test procedure is used above 15kV o What is the pass/fail criteria above 15 kV Thanks, Richard Woods --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
[SI-LIST] Immunity troubleshooting technique
Hi All, Well, its that time of the month when I get an itch to write something. So here goes Troubleshooting intermittent design problems can be a real time and resource burner in the development lab. Sometimes intermittent problems can be caused by lack of system immunity to noise on system cables. This month's technical tidbit at www.dsmith.org covers a technique for determining the magnitudes and relative directions of noise currents on system cables. This information can often lead to a solution of the problem. In addition, a design technique for minimizing system sensitivity to noise currents on cables is discussed. A modem example is used to show how the method is applied and scope data is used to illustrate how the data is interpreted. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- -- To unsubscribe from si-list: si-list-requ...@freelists.org with 'unsubscribe' in the Subject field For help: si-list-requ...@freelists.org with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu
Re: SONET ESD performance
Hi Scott and the group, Just a thought... If the equipment you are testing responds unfavorably to something the environment, it does not matter that you pass GR-1089. And, I have seen lots of stuff that affected lightwave equipment not covered under 1089 that got the operating companies pretty upset. For example, jingling change (we had a discussion some time ago on this list about this), but there are others. The customer expects the equipment to work the way he wants, not the way we design or the marketing org sells it, or the way it is tested. Give me a call or send email and I will briefly fill you in on what I have seen. It would be difficult to type it all here. Doug Scott Lemon wrote: Hi group, I am looking for guidance with respect to allowable service-affecting responses for a SONET system (e.g. OC-48) when tested to GR-1089 ESD immunity requirements. GR-1089 R2-3 states that service-affecting responses, unless within system operating limits,...shall not occur. Para. 2.3 gives maximum of one errored second per discharge as a limit on bit errors, but no other specific guidance. Anyone out there willing to share their GR-1089 pass/fail criteria for ESD testing on a SONET system with respect to performance during the discharge?? Are there any documents that are recommended as reference? Thanks in advance! Regards, Scott Lemon sle...@caspiannetworks.com --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
cable shielding effectiveness
Hi All, What do an AM radio, a copper tape spark gap, two paper cups, and a cable have in common? Together they can be used as a quick way to evaluate the relative shielding effectiveness of a shielded cable. This month's Technical Tidbit at http://www.dsmith.org uses the copper foil spark gap of last month's Technical Tidbit to generate severe EMI for testing the relative shielding effectiveness of a shielded cable. Data is presented for two different grades of RG-58/U cable. It could equally well be used to get an idea of the immunity level of a printed wiring board or electronic system. Techniques such as this can get you out of a tight spot in the lab while trying to debug a system. It seems the right equipment is never available so quick and easy tests such as this can be a real time saver. Also posted are pictures (link is just above the Technical Tidbit article at the bottom of the index page) of London and Oxford in England taken while on a trip to teach my high frequency measurement and design course at Oxford University last week. Enjoy! Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Static to dynamic field converter
Hi All, It is amazing what can be accomplished with simple, inexpensive test fixtures when it comes to debugging designs. The Technical Tidbit this month on www.dsmith.org describes a simple structure that generates repeatable, intense EMI useful for finding weaknesses in system designs. It also makes a good science fair project for a student. This article is a continuation of last month's article titled Hidden Threats to Electronic Equipment and is located near the bottom of the index page. The material cost for this gaget is about US$1 and it takes just a few minutes to build. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Re: EMC Courses in Europe
Hi Gunter and the group, The following link will take you to the Oxford University that has several short courses you may find interesting: http://www.conted.ox.ac.uk/ousep/ Doug gunter_j_ma...@embraco.com.br wrote: Colleagues I am looking for short (a week maximum) EMC courses in Europe during 2001. Topics of interest are : - EMC Design principles; - Suppression techniques for Burst, conducted EMI; - EMC x PCB design; - Measurement environments and testing (laboratory setup); - EMC standards (for Europe); - Practical demonstrations. Suggestions are welcome. Thanks Günter J. Maass Power Electronics Engineering EMBRACO S.A. Brazil --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
[SI-LIST] : Multi-GHz EMI from a static (DC) field
Hi All, It is a new month and here is my latest article. Doug Hidden Threats to Electronic Equipment Sometimes the connection between equipment malfunction and its cause can be difficult to make. This month's Technical Tidbit at http://www.dsmith.org covers a hidden form of ESD that has caused design engineers a lot of trouble in recent years. The article describes how simply bringing a coffee cup (or other object)that has a static charge near a piece of equipment can, under the right conditions, cause strong EMI with bandwidths to several GHz to originate inside of the equipment! Also described is a method to know when it is happening and to measure the potential for problems from the EMI. Click on the picture of the CD Player and coffee cup to see the article. -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- To unsubscribe from si-list or si-list-digest: send e-mail to majord...@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu
Re: ESD generators max Contact discharge level
Hi Glyn, Here is one way to approach 30kV. First, slide out of your car seat, the Ford Taurus is great for this effect. This puts a charge on your behind. As you get out of the car (everything is plastic so you remain charged with respect to the car) your voltage rises because Q=CV. Q stays the same (charge on your behind) but since C to the car goes down, voltage goes up. Then you go to close the metal door and a huge spark jumps between your hand and the door. Usually this results in jumping into the air muttering a few four letter words sometimes ending in (I am sure this happens with other cars, I just happen to own Fords, which I like) F O R D. I wonder why the car companies don't make seat material out of anti-static material BTW, contact discharge has the same risetime at all reasonable voltages, as opposed to air discharges, but still some equipment will fail at a low voltage and pass at high voltages. I can imagine a few ways circuits might do this. The effect is more pronunced with air discharge because of the risetime dependence on voltage (really arc length and whatever effects that, including speed of approach). Doug Glyn Garside(TUV) wrote: On the other hand very low voltage (and energy) events, such as jingling change have very high di/dt because of the tens of ps risetimes that occur at low voltage. I think this is why, as I recall, some (maybe all?) IEC standards require you to test not only to the ESD level indicated, but also the lower levels too. For example, if you are required to test at level 4, you are also required test at levels 3, 2 and 1. This is counter-intuitive -- Surely the highest voltage is the worst case? -- but apparently grounded in good physics, which Doug explains better than I would. PS: As to testing at higher levels than typical IEC values, I have read that the human body can, rarely, gain a charge of up to about 30kV(??), in conditions of low RH. Others may have better insight into this. Also, some manufacturers may want to build some margin into their test results: if five samples pass at 8kV, how sure can you be that the next 995 production units would also pass? PPS: I have a question of my own, drifting off topic slightly: if the relative humidity was fairly high when you passed the ESD test, and you retest (esp. air discharge?, or indirect discharge?) some months later when humidity is lower, could the same EUT now fail? (I think the answer is, yes?) Best Regards, Glyn Glyn R. Garside (mailto:ggars...@us.tuv.com) Senior Engineer, Industrial Machinery Division TUV Rheinland of North America, Inc. (Chicago Office) 1945 Techny Rd, Unit 4, NORTHBROOK, IL 60062-5357, USA http://www.us.tuv.com --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Re: ESD generators max Contact discharge level
Hi Dan, Contact discharge is meant to be applied to conductive surfaces. If a product has a plastic case, breakdown voltage (through seams and holes) is the important parameter. This is best done with air discharge, the object of which is not to have one. Doug Dan Kinney (A) wrote: While we're on the topic, I have a question (actually a couple) regarding air discharge. Since contact discharge is the preferred method, as stated in an earlier message and in EN61000-4-2, Paragraph 5, why would one perform the Air Discharge method? The same paragraph states Air discharges shall be used where contact discharge cannot be applied. What conditions would make it such that contact discharge could not be applied? Thanks in advance. Dan Kinney Horner APG -Original Message- From: Douglas C. Smith [SMTP:d...@emcesd.com] Sent: Friday, April 20, 2001 2:54 PM To: Terry Meck Cc: emc-p...@ieee.org Subject: Re: ESD generators max Contact discharge level Hi Terry and the group, Besides the question of finding a generator that can reach the level you mention, I am not aware of any natural ESD event that approaches the interference potential of even an 8 kV contact discharge. The problem comes in that high voltage air discharges have relatively slow risetimes, for 16 kV on the order of tens of ns, whereas contact discharges maintain a better than 1 ns risetime at all voltages. This makes for a much smaller dt to go along with the greater di to make a di/dt that is much higher, more than an order of magnitude, than you will see for these voltages in nature. Maybe if you were making atom bomb trigger mechanisms there would be a justification for this kind of testing, but not for real equipment. On the other hand very low voltage (and energy) events, such as jinjling change have very high di/dt because of the tens of ps risetimes that occur at low voltage. The combination of high voltage (and energy) with fast risetimes is too severe and meeting such a test is a waste of money for most equipment. Doug Terry Meck wrote: Hello again: Does anyone recall if there were any standard called for or ESD generator that simulated as the case may be = +-10 kV CONTACT discharge. We have a customer that is specifying passing +-16 kV ESD without referring to AIR or Contact discharge. I am inclined to ask what they have in mind since I have not seen any generators that go that high in the Contact mode. I suspect the writer of the SOW knows nothing and the engineering group only thinks Air Discharge. What do you all think? Terry J. Meck Accu-Sort Systems Inc. --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408
Re: ESD generators max Contact discharge level
Hi Terry and the group, Besides the question of finding a generator that can reach the level you mention, I am not aware of any natural ESD event that approaches the interference potential of even an 8 kV contact discharge. The problem comes in that high voltage air discharges have relatively slow risetimes, for 16 kV on the order of tens of ns, whereas contact discharges maintain a better than 1 ns risetime at all voltages. This makes for a much smaller dt to go along with the greater di to make a di/dt that is much higher, more than an order of magnitude, than you will see for these voltages in nature. Maybe if you were making atom bomb trigger mechanisms there would be a justification for this kind of testing, but not for real equipment. On the other hand very low voltage (and energy) events, such as jinjling change have very high di/dt because of the tens of ps risetimes that occur at low voltage. The combination of high voltage (and energy) with fast risetimes is too severe and meeting such a test is a waste of money for most equipment. Doug Terry Meck wrote: Hello again: Does anyone recall if there were any standard called for or ESD generator that simulated as the case may be = +-10 kV CONTACT discharge. We have a customer that is specifying passing +-16 kV ESD without referring to AIR or Contact discharge. I am inclined to ask what they have in mind since I have not seen any generators that go that high in the Contact mode. I suspect the writer of the SOW knows nothing and the engineering group only thinks Air Discharge. What do you all think? Terry J. Meck Accu-Sort Systems Inc. --- 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: http://www.rcic.com/ click on Virtual Conference Hall, -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Looking for alumni
Hi All, Not sure if this the right place to inquire about this, but here goes... I make electronic updates of my course notes available at no charge to people who have been students at one of my seminars. I have a good list of those that have attended my public seminars but my list from private in-house seminars at companies is not so complete. If you have attended my two day High Frequency Design/Measurement seminar in the last 3 or 4 years as a private seminar, send me email and I will give you instructions on how to download updated course notes. I have recently overhauled the course notes with lots of new information. The file sizes have increased about 3X. In the email message state the company name, city, and date where you attended the seminar. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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: http://www.rcic.com/ click on Virtual Conference Hall,
Unusual sources of signal corruption
Hi All, My Technical Tidbit article (http://www.dsmith.org) for this month deals with signal corruption of digital and analog signals by magnetic fields emanating from switching power supplies in a system. Because this is an unlikely source of corruption, it is often overlooked at great expense. The article covers an easy way to measure these fields to see if you have a potential problem. I would be interested in hearing other stories on unusual sources of signal corruption from others on this list. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
It's just a wire, isn't it?
Hi All, After a few weeks of holiday rush, I managed to write my technical article for January. And when is a wire, not just a wire?. After a few month's of articles on measurement techniques, this month's Technical Tidbit article on www.dsmith.org is more along the lines of design and system reliability. The article is about the amazing property of a conductor to develop significant series voltage drop across its length, even from an ordinary logic signal. Many engineers and technicians already know that the inductive reactance of a conductor exceeds its resistance at most frequencies, but even logic signals can produce volts of drop across the inductance in a short wire. The article also contains an amusing personal experience having to do with this effect. Go to http://www.dsmith.org for the article. I hope everyone had a good holiday season. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Probe construction
Hi All, For those of you who like to tinker in the lab (and sometimes we have to when the right equipment is not available), this month's Technical Tidbit (at http://www.dsmith.org near bottom of index page) describes how to make a shielded magnetic probe out of common materials (no semi-rigid coax needed). Such a probe is useful in many signal integrity and EMC investigations. Some uses for such probes are discussed in the paper on the site at http://www.dsmith.org/pdf/emc99-w.pdf titled Signal and Noise Measurement Techniques Using Magnetic Field Probes. Last month's Technical Tidbit showed how to measure ESD induced interference inside of equipment using a magnetic field probe. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Resistor design and ESD Symposium pictures
Hi All, The EOS/ESD (electrical overstress/electrostatic discharge) Symposium was last week in Anaheim, CA, USA. I focused on the system level effects of ESD, as a source of EMI, as opposed to controlling static charge. 18 representative pictures are now posted at www.dsmith.org under Miscellaneous next to the pictures of Veldhoven and Zug. Some of the pictures show useful and novel measuring instruments related to the EMI potential of ESD and other sources from companies like Barth and Credence as well as others. If you want to grab a picture, just right click (on a PC running Windows) the picture and enter the location where you want it to be stored on your machine. Links to the websites of the companies whose equipment is shown are also included in many cases. The Technical Tidbit for October relates to high frequency design of resistors for measurement or incorporation into designs. An example of a resistor from Barth Electronics is discussed. This is the design Barth uses in his DC to ~20GHz T-Pad that is described in an earlier Technical Tidbit titled Tapered Wall Cavity that I posted to the site exactly one year ago. The picture was taken at the Barth booth. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: compactPCI bus
Hi Bill, I missed your original posting (get hundreds of emails daily). Got to www.cpcibackplanes.com. You may find help there. That URL is the site of International Product Design, a local company here in Los Gatos, CA, USA. Shawn Arnold is one of the principles and I expect he can help. Doug Fleury, Bill wrote: Judging from the number of responses (0) I got to my question about EMI problems from compactPCI backplanes I am assumiong that either no one uses cPCI backplanes or I'm the only one that has experienced problems when testing in this environment. I didn't think that ever happened in this group. I'll repost this just in case some of you didn't get the last one. This is a question regarding systems which use CompactPCI bus architecture. On a cPCI backplane the PCI clock is routed to every slot on the backplane with up to 7 peripheral slots possible on a normal backplane. My question is this: With the cPCI specification calling out specific trace lengths for clock traces on both the backplane itself and on peripheral cards, have other people experienced any unique EMI problems in trying to meet the design constraints associated with this synchronous bus; especially where there are unpopulated slots on the backplane? Please feel free to respond privately if the question is unclear. I wasn't sure if it was worded properly. Thanks, Bill Fleury ***Artesyn Communication Products, LLC** Bill Fleury Email: bi...@artesyncp.com Compliance Engineer Phone: 608-831-5500 8310 Excelsior DriveFax: 608-831-8844 Madison, WI 53717 The difficult can be done immediately, the impossible takes a little longer (Army Corp of Engineers) *** Visit us at www.artesyn.com/cp ** Bill Fleury (E-mail).vcf -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Data Transmission System paper
Hi All, In response to several requests from members of these lists, I have posted a paper I authored titled EMC Performance Comparison of Shielded and Unshielded Data Transmission Systems presented at EMC'Roma 94. Both emissions and immunity (corruption or lack thereof of the data) results are presented. The results showed that a well designed UTP system (unshielded twisted pair) can perform as well or better than the commercially available STP (shielded twisted pair) systems tested. I wrote this paper while I was at ATT Bell Labs in 1994. The link to the paper is at http://www.dsmith.org (or alternately http://emcesd.com) under the heading Technical Information and Downloads. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: SAR
Hi Ron, I believe Elliott Labs in Sunnyvale, CA does such testing and have a very good customer focus. Doug ron_cher...@densolabs.com wrote: I am trying to get a list of labs that can perform SAR testing on the West Coast, (CA). Thanks, Ron DENSO --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Conducted Emissions on Telecom Ports
Hi All, I could not resist adding my two cents worth. In the last several years I spent at Bell Labs in NJ (moved to CA 4 1/2 years ago), part of my funding came from a group that was responsible for UTP (Cat 5) and associated hardware. On immunity performance, we were not able to find a shielded system that would outperform UTP using the interface circuits I had design input on. (When I first proposed the circuitry, the group had an internal Bell Labs balun expert review it. He did not understand how it worked.) Emissions were lower compared to several shielded systems we measured. The data was published at EMC Roma about 1995. If I can dig it up, I will try to post it to my site later this month. Several formats of data were used including 100 Mb speeds. We even did a demonstration of a 600 Mb over UTP cable (section of the cable is within sight at this moment). The conducted emissions on telecom leads spec was just being written at that time. As I recall, we were pretty close to meeting it except the method in the proposed standard was not workable, so we used current probes and moving the cables to maximize current (just like RE testing). The net result is that UTP with the appropriate interface circuits (not expensive, either) performs quite well compared to STP systems. If anyone wants more into, email directly to me and I will try and hook them up with someone at Bell Labs in NJ who is currently on the project. It's been a while and I am not sure what the present status of that work is. BTW, I recall that starting with a VERY well balanced source/load, Cat5 cable inherently had about 12 dB better balance, and therefore performance, than Cat3 for the high frequency immunity/radiated measurements that I made. I did not get much into the signal transmission differences between Cat3 and Cat5 though. Doug Gary McInturff wrote: Another little nagging problem exists. Without going into the whole historically precedence UTP was a pretty important reason why ethernet was adopted so widely. The wiring was pretty much in place because of the cables that had been run for connecting office telephones etc. People don't want to drag in new cables (STP) because of the cost. I happen to agree with you assements below and wouldn't even consider UTP if it weren't for the existing installs and the 805 standard that (prefers?) it. Thanks Gary -Original Message- -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
An interesting source for copper foil tape
...and what do slugs and snails have to do with circuit prototyping, debugging, or EMC work? Have you ever had a need for copper foil tape on short notice for circuit prototyping, debugging, or EMC work? This month's technical tidbit is on a source of such material, the local hardware store. Details are at http://www.dsmith.org at the bottom of the index page. The particular material described is the one I use for most of my measurement/EMC projects. The article is shorter than normal this month as I have spent most of the month on business trips including the IEEE EMC Symposium and preparing for next month's high frequency design and measurement public seminar. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Shielding Effectiveness - or when a dB is not a dB
Hi All, Shielding effectiveness is normally measured using plane waves (relatively far from the source). This method of measurement for shielding effectivenes does not always correspond to the way a shielding material is used. It is especially true when shielding material is incorporated into small products, such as the new wave of wireless devices on the market. If you rely on shielding to keep different parts of a product from interfering with each other, correlation of specification to use is especially important. The August 2000 Technical Tidbit on http://www.dsmith.org (or http://emcesd.com) describes a simple method of shielding effectiveness measurement that can be easily done in the development laboratory. This measurement method can give a better measure of shielding effectiveness that industry standard measurement techniques when the shield is close to the source being shielded. Has anyone here who is into shielding used something like this method which uses magnetic field loops? Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
[SI-LIST] : Hot ground noise probe
Hi All, I though some of you might enjoy my latest Technical Tidbit article. There are many techniques designers have used over the years to make quiet grounds on circuit boards and in systems. Sometimes it is done to reduce radiated emissions, other times to keep noise out of sensitive circuits. For July, the Technical Tidbit at http://www.dsmith.org (or alternately http://emcesd.com) describes an easily built resistive current probe using 6 resistors that among other uses, can be used to check for noisy grounds on a board or in a system. The probe is touched to circuit ground and its output gives an indication of how noisy the ground is and the likelyhood of the noise causing an emissions problem from a cable attached to that point of the circuit. Another use for the probe related to ESD and its theory of operation are included in the article. Just above the picture of the homemade resistive current probe (link to the article) near the bottom of the index page is a link to some pictures of Los Gatos I took recently. If you like armchair travel, take a look. The URL of the pictures is http://emcesd.com/losgatos/index.htm it you want to go there directly. Have a good Summer! Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- To unsubscribe from si-list or si-list-digest: send e-mail to majord...@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu
Probe ground leads
Hi All, Here is some light reading if you are looking for a way to pass a hot day (it is 109 degrees here in Los Gatos today!) Often, a probe ground lead is thought of as a source of error in a measurement. But, the ground lead can also increase measurement accuracy. I have posted a supplemental Technical Tidbit for June at www.dsmith.org on probe ground leads. It located at the bottom of the index page just below the main Technical Tidbit for June on 180 degree combiners. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Current Limitation for Single-Phase Power in the US and Canada
Hi All, 200 Amp single phase service is fairly common in the US (my present and last house has this service) so I know at least that much is possible. Separately, I posted sources for a couple of 180 degree combiners useful for differential probes at www.dsmith.org as this month's article. Last month's article was on measuring high frequency performance of small inductors and is archived under the Technical Tidbits section. Doug Doug wrote: Peter Merguerian wrote: Dear All, I was asked the ampere limitation for single-phase in the US and Canada? Can single-phase in the US and Canada handle 100-200 Amperes? Yes. Not sure if the question is really asking about the max. residential service amperage. So, for the size of the largest service entrance conductor and associated size of grounding conductor, see ... http://www.cmapc.com/Elect%20Files/EHtmFiles/GECTable250-94.htm For the associated ampacities of those conductors, see ... http://www.cmapc.com/Elect%20Files/EHtmFiles/Table310-16.htm The table maxes out at 705 amps. To calculate the size of the service needed, go to the following webpage, select the cell Sizing of Electrical Service, download the Excel spreadsheet, and enter the necessary info in the yellow squares. http://www.cmapc.com/_private/electsfr.htm Regards, Doug McKean --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Unusual System Glitchs
Hi All, We discussed at some length jingling change ESD and its relation to system operation some time ago. Along that line of unusual sources of system upset is multiple (up to hundreds) of ESD events in cushions of office chairs in the minute after a person rises from some chairs. The energy is radiated from metal legs and has wreaked havoc with many electronic systems, including those upon which human lives depend. I posted over the weekend my EOS/ESD Symposium paper titled A New Type of Furniture ESD and Its Implications which describes events of this type. The paper was awarded the New Phenomena award by the Symposium in 1993, the year it was published. You can see the paper at www.dsmith.org. Page down to Technical Information and Downloads and a link to the PDF file is listed in that section. The only evidence the events are happening is the EM fields radiated from the chair. The events are hidden inside the chair and not obvious to the person in the chair. I would be interested in hearing other stories from the group on system upsets caused by unusual immunity problems. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
50 Ohm Termination
Hi All, This month's technical tidbit article on www.dsmith.org is an easier way to construct a 50 Ohm termination good to 1 GHz or higher. Unlike my previous method, it is not necessary to try to solder surfact mount resistors to the rim of a BNC barrel adapter. The termination is useful by itself or as part of a high frequency probe. Next month's article will be Paperclips and the Speed of Light. It will be posted right after the first of the month. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
1996 IEEE Paper on EFT
Hi Again, I forgot to mention that I also posted my 1996 IEEE paper on an investigation of the IEC 61000-4-4 Capacitive Clamp. It is under Technical Information for Download. It covers measurement error and also data that suggests that the capacitive clamp couples much more EMI onto I/O leads than can occurs in cable to cable coupling. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Displaying measurement error and EFT testing
Hi All, I recently posted this month's article on my website www.dsmith.org. It shows how to display measurement error of a current measurement simulataneous to the measurement itself. This method catches almost all of the possible ways error can work its way into the measurement. The data I used for the measurement discussion also, as a by-product, shows how a common measurement error in Electrical Fast Transient (IEC 61000-4-4) testing can nearly double the stress on I/O leads of the EUT past what the test calls for at a given level. I have seen several test labs make this mistake, after the fact, by examining photos of the test setup in the test report. The error has to do with which end of the capacitive clamp is connected to the EFT generator. It makes a big difference! Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: 50/75 Ohm pads
Hi Jim, Barth Electronics of Boulder City, NV (702-293-1576) has some of the highest quality pads on the market with flat frequency response to 20 GHz and some with the ability to take hundreds or thousands of volt pulses (he designs for a specific voltage coefficient of resistance by making his own resistors). You can see one of his designs for a T-pad attenuator in an article I posted on my website in October titled The Tapered Wall Cavity at http://www.dsmith.org. Jon Barth's designs are quite elegant and very precise. Doug Knighten, Jim L wrote: Does anyone know where I can purchase 50 Ohm to 75 Ohm coaxial impedance matching pads, with low loss that are fixtured for SMA to SMA, or APC 3.5mm to APC 3.5mm connectors? Jim Dr. Jim Knightene-mail: jim.knigh...@sandiegoca.ncr.com mailto:jim.knigh...@sandiego.ncr.com Senior Consulting Engineer NCR 17095 Via del Campo San Diego, CA 92127 http://www.ncr.com http://www.ncr.com Tel: 858-485-2537 Fax: 858-485-3788 * Notice the Area Code change from 619 * - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Ferrites can increase emissions?
Hi All, I have noticed (like I expect many of you) that sometimes adding a ferrite on a cable to suppress common mode current caused emissions actually increases emissions at some frequencies. After thinking about this and trying an experiment to confirm one mechanism, I wrote up an article describing that mechanism. I have posted the article on my website (emcesd.com or www.dsmith.org) as the Technical Tidbit article for December. For the case shown there, a ferrite added at the OPPOSITE end of the cable from EUT2 would actually reduce emissions from EUT2 at frequency F2. Whereas if added at EUT2, emissions from EUT2 go down but go up from EUT1. Sort of an unusual case. Granted this is a special case, but the result is interesting and suggests lots of other possible configurations with strange results. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Ferrites can increase emissions?
Hi Ralph and all, Please define ground loop in your reply below. Normally, the term ground loop only has meaning at low frequencies (60 Hz and DC). At high frequencies an infinite number of loops exist and they do not require a conductor to complete them. You need to define exactly the effect for the particular case below. The special case in my article goes a level deeper than your discussion to show that ferrites at one end of a cable can either increase or decrease emissions from equipment at the opposite end by either causing an impedance match or mismatch. No ground loops needed to explain this phenomenon. Doug Ralph Cameron wrote: The purpose of a common mode choke whether it be of ferrite or powdered iron is to isolate the connecting conductors from the rest of the mainboard or chassis. If the toridal core is correctly placed as close to the source of the emissions i.e. the PCB, the conductors which carry the emitted noise are effectively isolated from high frequency noise currents to flow in common mode. The attenutaion will vary acording to the efficiency of the material selected and a permeability of a nominal 850 is useful over the range 3-40 Mhz. Some of the telphone companies use common mode chokes to attempt to suppress induced RF energy on phone lines and sometimes it works. They alsmot always specify placement of the in line encapsulated choke (ATT Z1000) at the wall socket. The amount of connecting cable from the phone to the wall socket is a good antenna too so picks up RF and bypasses any effect of the common mode choke. Although the problem is removing the condcuted current before it becomes a problem , the same principle applies to emitted noise. In some cases of suppressing consumer equipment there is a dramatic increase in sensitvity to conducted currents at different frequencies( usually higher) and this requires that the ground loop provided by the power cord be isolated from the device. Inevitably this has cured the problem. Be aware that any cabling connected to a device can radiate as well as conduct undesireable energy into the device. Ferrites provide a simple, non intrusive, inexpensive solution to such problems. You will see them on all the better quality computer monitors and laptops. Ralph Cameron Independant EMC Consultant and suppresion of consumer electronics (After sale) - Original Message - From: Douglas C. Smith d...@dsmith.org To: emc-pstc emc-p...@majordomo.ieee.org Sent: Wednesday, December 01, 1999 9:46 PM Subject: Ferrites can increase emissions? Hi All, I have noticed (like I expect many of you) that sometimes adding a ferrite on a cable to suppress common mode current caused emissions actually increases emissions at some frequencies. After thinking about this and trying an experiment to confirm one mechanism, I wrote up an article describing that mechanism. I have posted the article on my website (emcesd.com or www.dsmith.org) as the Technical Tidbit article for December. For the case shown there, a ferrite added at the OPPOSITE end of the cable from EUT2 would actually reduce emissions from EUT2 at frequency F2. Whereas if added at EUT2, emissions from EUT2 go down but go up from EUT1. Sort of an unusual case. Granted this is a special case, but the result is interesting and suggests lots of other possible configurations with strange results. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q
ESD data
Hi All, I have posted on my website the November article. It is related to the recent ESD and grounding threads on the Si-List and emc-pstc lists. Go to http://www.dsmith.org or http://emcesd.com and click on the picture at the bottom of the index page (after trying to guess the answers to the questions above the picture). Also newly linked on the index page is October's article on a Tapered Wall Cavity to achieve a T-Pad design flat to tens of GHz and pictures of Veldhoven, Netherlands where the recent meeting of TC77B was held. WG9 (charged with rewriting IEC 61000-4-2) was part of the meeting series that I attended. Enjoy, Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Home-Made RF probes.
Hi Kyle, It is important that the gap in the shield be exactly on the opposite side of the loop (as I believe you cite in your construction details). The loops with the gap at the end of the coax that is bent around do not actually have much electric field shielding. The details are in my paper from last year's EMC Symposium. The paper in pdf format is on my website at www.dsmith.org or emcesd.com. Doug Ehler, Kyle wrote: Greetings, 15 years ago I was doing some work at SWRI in San Antonio where I watched an EMC tech construct two RF probes from small diameter copper jacket hardline (semi-flex coax?). These probes resemble a kid's toy soap bubble loop, but they work wonderfully well for non-contact source investigation of radiated emissions ranging into the Ghz region. Our lab still uses these for debug work to this day, but now they are a bit worn and I suspect they will need replacing. Trouble is, I'm fuzzy on their construction details. Below, please peruse the steps I recall and offer any corrections or improvements. I have attached a couple .jpg's for clarity (hope I didn't stretch the rules). -For the high resolution probe (see photos): 1) Start with 6 to 8 length of 0.0625 copper jacketed solid conductor hardline for 0.5 diameter probe. 2) Remove 0.125 of jacket and insulation from one end. 3) Roll-form stripped end of coax into 0.5 diameter loop with exposed center conductor and jacket touching probe shaft jacket. 4) Solder center conductor of loop to jacket first, then outer jacket of coax end to jacket of probe shaft. 5) With a sharp knife (X-Acto) cut a 0.010 concentric ring out of the jacket at the apogee from the probe shaft, exposing the center conductor, but not cutting it (ok to leave foam insulation intact). 6) At other (handle) end of probe shaft, affix a female BNC (or SMA?) connector (your choice?) and carefully solder fillet 360' of connector to jacket. 7) Dip finished probe twice into 'Plasti-Dip' of your choice colour. Let cure in between coats and before use. -For a low resolution probe: Substitute 0.125 hardline in 1) above. Form loop into 2 diameter in 3) above. The small loop and a wideband preamp is really good for non-invasive pinpointing the source of radiation (chip, trace, xtal, etc.). hi res loop.jpg hi res probe.jpg Kyle Name: hi res loop.jpg hi res loop.jpgType: JPEG Image (image/jpeg) Encoding: base64 Name: hi res probe.jpg hi res probe.jpgType: JPEG Image (image/jpeg) Encoding: base64 -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Printed Circuit Board Grounding
Hi Don, Each situation should be evaluated on its own merits. I am going to list some general rules of thumb below, but there may be exceptions. I have done lots of ESD current measurements in different configurations and base my opinions on these measurments and personal experience with equipment. 1) Any piece of metal will absorb high frequency components of ESD from a wire that it touches, the bigger the metal, the lower the frequency of components it will remove from the wire. The metal need not be grounded, its free space capacitance is enough. I have done an experiment that shows this hundreds of times in my seminars. So if a cable touches its shield to a metal chassis on the way to a circuit board, the chassis will remove most of the high frequency components of the ESD. 2) I have observed cases where grounding a PWB to the chassis at many points solved ESD problems and removing connections caused ESD problems, but never the other way around although there may be special cases where it could happen. This is likely related to 1) above. If you have doubt about a particular configuration, don't guess, measure and see what really happens. If you are not sure how to do this, call or email me and I will help you plan an experiment to measure your case over the phone or email. 3) If you ESD to the outside of a chassis, the currents will stay on the outside of the chassis because of skin effect. Holes and seams can let the current in, but the high frequency content will already be reduced by 1) above. Unless you have gaping holes, multiple connections to the chassis from the circuit board are not usually a problem (remember this can be measured). 4) An interesting thought: even 1 pf of capacitance can easily couple a few amps of ESD current under many conditions so it is almost impossible to isolate the PWB from the chassis anyway! Doug UMBDENSTOCK, DON wrote: Hello Group, We are having a debate concerning the best practice for grounding of a printed circuit board containing digital logic. These boards are multi-layer with a ground plane and a power plane. One school of thought is to tie the ground plane to chassis ground in many locations, thus reducing the impedance. Another school of thought says to control the point(s) that is (are) tied to ground or risk upsetting of sensitive circuits with an ESD or other immunity event. The concept is that an ESD event may be decoupled to chassis at the I/O ground plane with the use of appropriate circuit elements to control impedances. Now consider the chassis to be steel, and the digital ground plane to be copper. If the digital ground plane is stitched to chassis in several locations, it appears that a lower impedance path (copper vs steel) will encourage the ESD to travel across the ground plane. If the ESD travels across the digital ground plane, there appears to be a good chance of upsetting sensitive circuits. So the thought might be to tie only one point of digital ground to chassis ground, thereby not providing a path for any immunity event to flow across this ground plane. The rest of the above concept is to use moats to segregate key circuits -- digital, I/O, analog, switch-mode power supplies. Again, some say to keep the ground plane in tact to provide the lowest impedance reference possible, so isolation is provided by carving up the power plane. The alternate approach is to carve all the way through, i.e., if you have a moat around a particular circuit, if you are going to isolate, do it for all planes (stack, do not overlap). This latter approach, however, carves up the ground plane which would appear to increase the impedance of the overall ground reference. The argument is that carving up the ground plane is justified by eliminating the coupling of dirty ground to other circuits in an overlap situation. I would like to hear what you do for pcb grounding and why you do it. Don Umbdenstock Sensormatic - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc
1999 paper posted
Hi All, I decided to post my 1999 IEEE EMC Symposium paper on magnetic field probes, Signal and Noise Measurement Techniques Using Magnetic Field Probes, as well as the current probe paper. The 1999 paper provides background for last month's Technical Tidbit on the paperclip probe. The 1999 paper is a bit long (~600K) because of more graphic content. It is much shorter that the nearly 2 Megabyte file on the CD-ROM that was given out at the Symposium even though it has much better resolution Both papers can be found under Technical Goodies for Download near the top of my index page at: http://emcesd.com Happy reading! Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
measuring voltage drop with a current probe
Hi All, I thought some of you might find my technical article of the month interesting. It is on making voltage measurements with a current probe. Over much of the useful frequency range of a current probe, its output is not the current in the wire but rather the voltage drop along the wire per unit length. The waveshape of the probe output is that of the voltage drop along the wire (di(i)/dt), not the current in the wire (i(t))! If this sounds interesting, click on the current probe picture at the bottom of the index page on my website at http://emcesd.com for a technical discussion along these lines. Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Immunity Problems ??
Hi All, ESD or EFT could be the culprit. I would suggest putting a current probe around one of the instrument cables and connect to a digital scope and see if you can trigger on a noise event. If you are lucky, the instrument with the current probe will be the one that goes down. Alternatively, connect a small antenna to the scope, set to 50 Ohm input, set the V scale to 100 mV/div, H to 20 ns/div, and trigger on a 50 mV positive going edge for starters. If you get nothing or too much, adjust the parameters accordingly. A 6 inch diameter loop of wire makes a good antenna. Doug Price, Ed wrote: Joe wrote: -Original Message- From: marti...@pebio.com [SMTP:marti...@pebio.com] Sent: Tuesday, September 07, 1999 2:04 PM To: emc-p...@majordomo.ieee.org Cc: marti...@pebio.com Subject:Immunity Problems ?? EMC Professionals, We have 42 of the same instruments installed in one laboratory. What are they? What type of power feeds and I/O lines or sensors? What about physical separation? They are each installed on their own dedicated line. Powerline? On a regular basis The toughest problems are unpredictable, intermittent failures. This is your first ray of hope; you should try to associate the problem with external conditions; i.e., a step in your process, the plant elevator, the air conditioning, every 107 minutes, something. an instrument will shut down during a run. A bit more description about the shutdown. The instrument that shuts down is different each time. Really, NEVER the same instrument? Or do you just mean it strikes randomly? These instruments are laboratory equipment that meet Class A radiated limits of EN 55011 and meet the immunity requirements of EN 50082-1. So, then you really don't have a problem? (Sorry, grin!) Any ideas as to the potential cause of the problem and possible ways to resolve the problem would be greatly appreciated. Well, you can start right away with the correlation effort. You could also put a powerline monitor on the power buss. If you operated one instrument without I/O or data or control leads, you might start to get an idea about the problem if that one instrument NEVER shutdown. That might say the problem is not coupled through the power bus. OTOH, if it failed just as the others, that may lend weight toward the power bus as the path. Can you operate an instrument in another building? Do you get zero shutdowns, or the same probability? Can you operate a cluster of your instruments in a remote location, and do they exhibit shutdown problems too? Regards Joe Martin EMC/Product Safety Engineer P.E. Biosystems marti...@pebio.com That's enough for now! Organize your info and get back to the list. Regards, Ed :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 (Voice) 619-505-1502 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
1 GHz probe theory
Hi All, I have added a theory of operation section to the 1 GHz probe plans on my site at: http://emcesd.com The section discusses why the foil is needed and the underlying limitation on the useful frequency range of the probe. Also added is the ability to click on the probe pictures to blow them up to full screen size, instantly. You can even clearly read the values on the surface mount resistors! I am interested in any comments on the theory addition (correctness, readability, etc.) Also posted is the discussion on this month's problem of how to measure circuit voltages with a paper clip. Thanks in advance, Doug -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
