Couldn't agree more. Nice summary Patrick. At EchoStar we strive to meet or exceed the stated measurement uncertainty of the test site. That seems reasonable and has some sort of science to it. Other that that your questions are very apropos.
Best Regards Charles Grasso Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Pager/Short Message: [email protected] Email: [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Conway, Patrick R (Houston) Sent: Tuesday, June 26, 2007 4:01 PM To: Kunde, Brian; [email protected] Subject: RE: Internal Margins for Emissions Testing It seems from Brian's email, and the responses so far, that test margin is a presumption. Why? Why is it presumed that we need any margin at all? If we can answer that question, then the "amount" of margin needed should follow easily. Here are some basic questions we compliance engineers should ask of our companies. What problem do we solve by having margin during testing? (If there is not a well defined problem, then we should stop right here!) Does that problem get solved "better" by adding more margin? (can you show that doubling your margin improves your problem solution by 2x ? ) Are the percentages, probabilities and uncertainties associated with that margin truly defensible? (defensible in a mathematical and manufacturing sense, not a legal sense) If a problem occurs in the field, does the required margin shown in the test report gain you any advantage in discussions with the customer or auditing body? (so, you did one test and passed. Then you manufacture 10 million a month. What does that margin buy you?) IMHO - these are the basic questions a company should answer before committing to any compliance plan. Best Regards, Patrick. [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, Brian Sent: Tuesday, June 26, 2007 12:13 PM To: [email protected] Subject: Internal Margins for Emissions Testing Good people of the EMC-PSTC Group, I once again seek out your wisdom. We are an internal corporate EMC/Safety test lab. Most of the EMC testing we do are either Pass or Fail. But with Emissions testing (Radiated and Conducted) we want to pass with enough margin to insure our production stays compliant. The amount of margin that is accepted is always in debated between our department and engineering. I'm sure many of you have had similar problems. My question is how do you convey the desired margin on your test reports or other documents so the standard limits and internal limits (with margin) are properly documented and hopefully understood. Do you show two limit lines on your graphs an/or multiple limits and margins in your data tables? How does your Measurement Uncertainty factor into your data and how it is reported/documented? How are emissions requirements conveyed to engineering so they know what they are to design to (Limit plus some margin)? I know this seems like a newbie questions, but I am hoping that some of you have found cleaver new ways of dealing with this problem which has been around since the beginning of time. Thanks in advance for any and all replies, The Other Brian. LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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