Brian We have established the desired margin in our internal Division Policy on EMC. The definition is based on measurement uncertainty, and some product experience (what manufacturing deviations can be expected). In the Conducted Emissions Plots there is a green line showing with the caption '-8dB', which is our defined test margin, and the test plan shows the desired margin as 'Recommended Performance'. The radiated emissions results do not have any indication of the desired margin. The alternative provided is to achieve a 4 dB margin with 80% confidence of 80% compliance (the old 80-80 rule) on a maximum sample of 5.
John Mowbray, P. Eng. Senior EMC Engineer NCR Canada, Ltd. 580 Weber St. N. Waterloo, Ontario N2J 4G5 519 884 1710 X5371 [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, Brian Sent: June 26, 2007 1:13 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. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
