Whoah Ed, you just landed along side Ken and Ghery!
I have to strongly oppose some of your views on what the test lab should or shouldn’t Know/do. Wow, have you any idea of the variety of equipment that roles in the lab door, and the complexity of it? NO, it is NOT the labs job to understand the EUT, other than how to interpret the standard so it can be tested. It is totally unreasonable to expect a test person to muse the subtleties of sub micron silicon one day then the ramifications of 10,000 psi hydraulic pumps the next. I doubt few could listening in. Having had the luxury of “visiting" well over 350 labs around the globe over the last 23 years I’ve gathered quite a bit of insight on lab operations and their clients. I happen to have worked in one for 40 years and owned one or two for 30+ years. So much of the email thread is huff and puff. IN the sales world it would be called FAD: fear and disillusionment. Lets set some records straight: The majority of labs do a superb job with all the constraints they are under. An ISO 17025 assessment cannot prevent mistakes, but it does make provisions for just about all foreseeable, and quite a few unforeseeable problems. Everyone can have a bad day: that includes test engineers/technicians. Technology evolves, and what’s true at one point may not be true sometime later. Unless everything is checked to the nth degree, EVERY time, things will escape notice. For all those calling out check after check, I bet under the same breath they are complaining about the cost of testing! And for the record, those critical of overseas test labs should go and pay a visit: most times they are careful to incredible levels running tests. If a manufacture brings a device in for testing, no-one, that’s NO-ONE knows it better than he does. He has a responsibility to understand the testing his device will be subjected to and its behavior, heck, he’s supposed to have designed the device to pass the test! That includes support equipment too! A lab should help someone who’s a novice in the EMI field to avoid pitfalls, that’s professional curtesy. It’s also in the labs interest as they don’t want someone packing up and leaving a few hours into the day and leaving the rest of the day not generating revenue. This topic is huge, and I hear so called experts spout contentious opinions that are ill founded. It’s particularly distasteful especially in a professional form such as this as it forms false opinions in peoples minds, especially as some of these experts have a high platform from which to pontificate. There isn’t a rampant problem in the testing community, and many hardworking technicians, engineers, managers, QA people, Assessors, assessing bodies and even test witnesses would be very aggrieved to hear some of these statements. Testing is a team mentality, not a glass wall mentality. And valid data is the responsibility of BOTH parties. It requires capable people who have a systematic work approach. So unless ALL the full details are known spreading scuttlebutt or opinions of what could have/should have, is NOT helpful. My 10 cents as I have to go back and tend to a test I’ve been running since 6am. Shalom. Derek. > On Apr 17, 2019, at 6:21 PM, Edward Price <[email protected]> wrote: > > Derek: > > When a test lab is engaged to perform testing on a product, the test lab owes > the client, at the minimum, accurate test data. However, it is not the > “chamber” that delivers that assurance of quality workmanship, rather it is > the EMC Engineer in charge of that facility. When the client walks in the > door, he expects a knowledgeable testing operation, not an environment that > seems to be learning as they go. Not recognizing Ambient noise polluting the > Operational emission data is a failure to deliver the expected professional > level of competence. To me, it seems pretty clear that the testing lab is at > fault. If the problem was rapidly recognized by them, and a new set of data > was taken, then the problem is mainly one of embarrassment of the testing > lab’s people. However, if it goes on without recognition, if the lab lets the > client take his equipment home with the assumption that the equipment has > failed, then the longer it goes on, the greater the testing lab’s error and > financial responsibility becomes. Perhaps the testing lab never noticed the > problem on their own? That would have been a pretty serious indication that > the testing lab just wasn’t ready to deliver professional quality testing > services. > > Another interesting comment was that there was difficulty in “setting up” the > test specimen and its support equipment. A good test lab will know what a > customer needs to supply long before the test date. Time should be budgeted > for the setup and trouble-shooting of ancillary devices, and the customer > should be warned that home-brew support equipment may cause EMI issues all on > their own. A good test lab will make some suggestions about best practices, > but alert the customer that it may be necessary to ameliorate support > equipment problems before EUT testing can begin, and this may entail > additional time and materials needed to make the support equipment quiet or > immune enough to allow testing. Further, a good test lab should always expect > some set-up problems, and be ready to surmount these with a plentiful junkbox > of rolls of aluminum foil, conductive tape, bond straps, shielded boxes, > knitted wire mesh, capacitors, inductors, ferrite beads, isolation > transformers, sheet metal and a decent assortment of common hand tools. In > short, if your customer says his gadget needs an external water chiller, the > test lab should have already thought about ground loops, how to get water in > and out of the chamber, and have considered what problems a water chiller > might induce in the lab’s electrical environment. The test lab’s customer > should not feel that the test lab was unprepared to receive him or that the > test lab was anything less than expert in integrating the test specimen and > support equipment into the test chamber. > > It would appear that the selected test lab was just not ready for prime time. > > > Ed Price > WB6WSN > Chula Vista, CA USA > > From: DEREK WALTON [mailto:[email protected] > <mailto:[email protected]>] > Sent: Wednesday, April 17, 2019 12:08 PM > To: [email protected] <mailto:[email protected]> > Subject: Re: [PSES] Question re: Measuring a signal in a noisy environment > > 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] > <mailto:[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. 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]>
