I'll dare to mention a few errors which I have seen first-hand; I would say that these are all in the "we don't know what we don't know" category.
. Having an abiding faith that mixers can handle any power you push down a coax. . Thinking that coaxial directional couplers are as broadband as the coax. . Assuming that components must blow smoke before death. . That amplifiers only amplify. . That signal sources are clean. . Not realizing that coax cables are not water pipes, and that stacking several 3-way Tees at a junction will have no effect on impedance. . That anything performs as promised without cross-checking. . That what was good last week is still good. . That the little mistake you made earlier couldn't have any cascading effects. . That the software knows what it's doing. . That you know what the software is doing. . That you have all the variables under control. . That everyone wants to know the truth. Ed Price WB6WSN Chula Vista, CA USA From: Kunde, Brian [mailto:[email protected]] Sent: Monday, December 01, 2014 1:56 PM To: [email protected] Subject: Re: [PSES] EMC test lab errors Doug, Ok, you got my curiosity going with your examples. How about a little more detail? If "every test lab where I have been" is doing something wrong maybe it would be nice to know what it is. What could be wrong with my ESD table? What shortcut could be causing higher Rad Emm reading? If every lab is doing the same thing, doesn't it become "standard"? hee hee. The Other Brian From: Doug Smith [mailto:[email protected]] Sent: Monday, December 01, 2014 2:31 PM To: [email protected] Subject: [PSES] EMC test lab errors Hi All, I just posted my latest Technical Tidbit on EMC lab test errors. Unfortunately these are more common than one would hope, sometimes "failing" a passing product and sometimes "passing" a failing product (may not be as desirable as first appears). Abstract: EMC testing is a required part of bringing a product to market. Passing the test itself can be a real headache for developers and marketers, but what if the test was performed in error and the test results are not valid! This is a real problem in the more general field of lab testing as well as specifically EMC testing. Some thoughts are shared on the topic. The link to the article is: http://www.emcesd.com/tt2014/tt120214.htm Other links on my site of interest: http://emcesd.com A new phenomena! Some system power supplies can convert a system ESD hit into dozens of ESD hits and even convert EFT on the power line into nasty ESD hits even when the applied pulse is a small fraction of the power supply breakdown voltage! Some of the characteristics are: Some of the nastiest ESD waveforms you will ever see. Over a period of a few microseconds, many Human Metal Waveforms, Cable Discharge Waveforms, corona discharges, and ESD events embedded in other ones, of both polarities can be generated from a single ESD event applied to the product. It is like every possible ESD waveform that can be, is generated from a single applied ESD event. The results have been duplicated in three different laboratories with different scopes, different ESD simulators, and different power supplies. And, this effect often happens at a small fraction of the rated barrier breakdown voltage of the power supply! To date, this newly discovered effect has been observed in small power supplies operating off the AC mains with a two wire interface, but it is possible others may have the same response. These kind of power supplies can include small supplies directly plugged into the mains, brick type supplies used with PCs, and equipment with a two wire mains interface like: stereo amplifiers, set top cable and satellite boxes, a lot of consumer equipment, and some industrial equipment. I have dozens of waveforms I have taken on this effect resulting from both ESD and EFT. http://emcesd.com Almost 300 papers, articles, and videos are not posted on the site! Great cure for insomnia. Doug -- University of Oxford Tutor Department for Continuing Education Oxford, Oxfordshire, United Kingdom -------------------------------------------------------------- ___ _ Doug Smith \ / ) P.O. Box 60941 ========= Boulder City, NV 89006-0941 _ / \ / \ _ TEL/FAX: 702-570-6108/570-6013 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Web: http://www.dsmith.org -------------------------------------------------------------- - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
