Interesting discussion, not surprising I have a little empathy, and a whole slew of disagreement with both Ken and Ghery ( both Chaps I have a lot of respect for ) on this one.
How best to respond is the question? Cheers, Derek Walton. > On Apr 17, 2019, at 1:12 PM, Bill Stumpf <[email protected]> wrote: > > Absolutely agree with Ken. > > Bill Stumpf > Lab/Technical Manager > D.L.S. Elecronic Systems, Inc. > > > > From: Kenneth Wyatt [mailto:[email protected] > <mailto:[email protected]>] > Sent: Wednesday, April 17, 2019 12:21 PM > To: [email protected] <mailto:[email protected]> > Subject: Re: [PSES] Question re: Measuring a signal in a noisy environment > > Boy, I have heard all sorts of horror stories from clients with knowledgeable > EMC backgrounds who have witnessed sloppy, or just plain wrong, procedures > used in commercial EMC test labs. In a lot of cases, the technicians > operating these tests have limited background in EM theory and poor knowledge > of the actual tests they are running and standards the tests are based on. > > Just because a test lab is assessed per IEC 17025, doesn’t mean much unless > they show evidence the documented procedures are actually being followed. > > Many test labs fail to perform frequent verification tests to confirm the > measurement system is accurate and is repeatable from one day to the next. > When I worked for HP, we did a daily verification test using an RF generator > connected to the antenna cable to ensure the back-end system measured the > same as the day before. We also ran comb generator tests frequently. > > I always suggest to my clients to make their preferred test lab measure a > client-owned comb generator prior to any testing in order to ensure the > chamber continues to be reasonably consistent before real measurements are > taken. > > It’s also very important to understand the test standards and EUT > configurations well enough to ensure the test technician is setting up things > correctly. I know of one case where the EUT cabling was configured wrong and > their client repeatedly had emissions failures over weeks of retesting until > the correct configuration was pointed out in the standard. > > Taking photos of the test setup is very important for day to day test > consistency. A difference in one cable position can completely throw off > repeatability and thus, mislead any troubleshooting efforts. > > What about ESD simulators? When was it verified last? Does the test lab even > have the means to verify the correct tip voltage and pulse characteristics? > > Is all the measurement equipment calibrated and cal tags current? > > I could go on… > > My colleague, Ghery Pettit wrote a recent blog on the subject for > Interference Technology: > https://interferencetechnology.com/emc-laboratory-selection-audit-items/ > <https://interferencetechnology.com/emc-laboratory-selection-audit-items/> > > Cheers, Ken > > _______________________ > > I'm here to help you succeed! Feel free to call or email with any questions > related to EMC or EMI troubleshooting - at no obligation. I'm always happy to > help! > > Kenneth Wyatt > Wyatt Technical Services LLC > 56 Aspen Dr. > Woodland Park, CO 80863 > > Phone: (719) 310-5418 > > Web Site <http://www.emc-seminars.com/> | Blog <https://design-4-emc.com/> > The EMC Blog (EDN) > <https://www.edn.com/electronics-blogs/4376432/The-EMC-Blog> > Subscribe to Newsletter > <http://www.emc-seminars.com/Newsletter/Newsletter.html> > Connect with me on LinkedIn <https://www.linkedin.com/in/kennethwyatt/> > > > On Apr 17, 2019, at 10:46 AM, Grasso, Charles <[email protected] > <mailto:[email protected]>> wrote: > > To those wondering what the background and conclusion to that question was: > > Background: Our testing was performed in a newly minted chamber so > proper > EMC installation of our product was challenging. > Effect: Ingress of high levels of external bb noise. > Result: Proper install eliminated the external noise and now > the system passed. > > Concern: While I accept that proper installation and operation of our system > is our > responsibility, I had expected that the tester would point to the excessive > ambient > and indicate that our data may not be valid. An inexperienced customer would > have left thinking that their product had failed. > > Am I wrong? > > > Thanks! > > Charles Grasso > W: 303-706-5467 > > - > ---------------------------------------------------------------- > > 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] <mailto:[email protected]>> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > <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/ > <http://product-compliance.oc.ieee.org/> can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ <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 > <http://www.ieee-pses.org/listrules.html> > For help, send mail to the list administrators: > Scott Douglas <[email protected] <mailto:[email protected]>> > Mike Cantwell <[email protected] <mailto:[email protected]>> > > For policy questions, send mail to: > Jim Bacher <[email protected] <mailto:[email protected]>> > David Heald <[email protected] <mailto:[email protected]>> > > - > ---------------------------------------------------------------- > 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 > <[email protected] <mailto:[email protected]>> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > <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/ > <http://product-compliance.oc.ieee.org/> can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ <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 > <http://www.ieee-pses.org/listrules.html> > For help, send mail to the list administrators: > Scott Douglas <[email protected] <mailto:[email protected]>> > Mike Cantwell <[email protected] <mailto:[email protected]>> > > For policy questions, send mail to: > Jim Bacher <[email protected] <mailto:[email protected]>> > David Heald <[email protected] <mailto:[email protected]>> > - ---------------------------------------------------------------- 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 <[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]>
