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]> 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. 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]>
