Re: [PSES] Stricter limits than legal (CISPR11, IEC, etc,) Where?

[Douglas Powell]

Ted, Very good points. If minimum passing margins are a result of ‎edge rates on transistors, diodes or ICs, then a second source or "upgrade" to a faster device can be counterproductive with regard to the emissions profile.   If such engineering changes or supplier changes have occurred, then a retest is often the best policy. I was also aware that several cumulative engineering changes over time can result in a non-compliance.    â€ŽEach change, when evaluated by itself was inconsequential. But in aggregate, result was a failure. This is often the reason I would require a retest after some number of engineering changes had been applied to a product.  Of course, keeping full data test reports on each passing result is really the only way to do this well.   Doug Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01   From: Ted Eckert Sent: Monday, October 12, 2015 2:44 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Reply To: Ted Eckert Subject: Re: [PSES] Stricter limits than legal (CISPR11, IEC, etc,) Where? In addition to the responses from Doug, Ghery and Brian, I will note that margin protects you from unexpected or unknown changes from component suppliers. To some extent, this falls under the manufacturing variance Doug mentioned, but component changes is just another area that can be hard to control.   I’ve had IC vendors do a die shrink on a part resulting in sharper edge rates on the outputs. At a previous employer, I was running emissions testing on a number of samples where Motorola did a die shrink on the microcontroller we were using. Some of my test samples had the old part and some had the new. It took a long time to figure out why some samples were significantly worse than others after controlling for all other variables. Having 6 dB margin to begin with provides some protection against this type of change.   Ted Eckert Compliance Engineer Microsoft Corporation ted.eck...@microsoft.com   The opinions expressed are my own and do not necessarily reflect those of my employer.   From: Itzenheiser, Jerry (GE Healthcare) [mailto:gerald.itzenhei...@med.ge.com] Sent: Monday, October 12, 2015 12:26 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Stricter limits than legal (CISPR11, IEC, etc,) Where?     Hello EMCers, I would like to ask… Is there anyone out there that tests to stricter limits than the legal (CISPR, IEC, etc.) limits? If so, what was the rationale behind selecting the stricter limits? Our engineering teams are curious as to where the stricter recommended limits come from, such as the 6dB margin for emissions testing.   Thanks,   Jerry Itzenheiser Jr EMC Technician - Waukesha GE Healthcare Global Engineering Technologies EMC Laboratory Waukesha   T  + 262-548-2217 M + 262-720-8846 gerald.itzenhei...@med.ge.com www.ge.com   3000 N. Grandview Blvd. Mail Code W618 Waukesha, WI  53188   - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>