Some people may take that approach, known in British English as 'by guess and by god' (whichever god). But there IS math that not only should give the people involved more confidence, but provides evidence for convincing managers, surveillance officers, and, in the last resort, the judge, that everything is in order. The document whose URL I gave explains in fairly simple terms how to use the math. With best wishes John Woodgate 3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO – Own Opinions Only <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and Associates Beware averages! They hide or discard data, and may distort it (them?). From: Patrick [mailto:conwa...@gmail.com] Sent: Friday, September 1, 2017 4:21 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] God EMC practice God and Compliance Margin... two topics that generate a lot of preaching! I think everyone has a "tradition" of what worked for them, and what did not. Here is my sermon on margin: I don't consider myself a monk of the EMI Chamber... ...but over the years I have preached various margins. ...margins are always situational, always depending on the business, and the products. ...call it relativism? On one end of the extreme, I've been in the aerospace industry. Here, a single unit is built, and flown successfully, with *zero dB* of margin. On the other end, consumer products. Here, just one or two units comply during development. Then the factory produces a million units a month for a year. Yes, that is 12 million units based on a couple of passing samples! In this industry, initial margin can not predict performance of the 500,00th unit. So, the industry performs on-going EMC audits. In both those cases, the dogma of margin was irrelevant. For aerospace, what mattered was coexistence. For commercial, it required an ongoing liturgy of audits. What really drives margin is the product, the market, and the target usage. Everything else is just "tradition" & "hearsay". Every company needs enlightened margin decisions based on their own circumstances. Thanks for the bit of humor to end the week! -Patrick On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen <k...@bolls.dk <mailto:k...@bolls.dk> > wrote: Hi One of our customers want to know if there are some good practice for emission compliance. I normally recommend 3 dB margin, but I don't have any reference to why this is OK. I know that some companies have internal rules for 3 or even 6 dB margin to compensate for production deviations and for many years ago VDE did have some rules like that. Does anyone have some good references on this subject? Best regards, Mr. Kim Boll Jensen - ---------------------------------------------------------------- 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 <mailto: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) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> >
-- // Patrick - ---------------------------------------------------------------- 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 <mailto: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) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto: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>
