Bill et al, IMO there is no easy answer to the problem of one area of test provoking design changes affecting another area of test. A diverse product line, such as individually sold PC cards and a line of complete systems, would call for a different approach as needs demand (often cost considerations come first).
I don't think you were concerned over loss of a sample (by catastrophic damage). But, safety usually includes fault testing that could render a sample damaged beyond repair (even though it might pass safety). Even a successful repair of the sample could hide component stresses that could bias the EMC test results. I prefer to test in parallel with two or more samples so fixes can be weighed together. (Of course the cost considerations must be reasonable.) Though as I've encountered just asking for more samples can be impractical when each sample - of even a small PC card - are difficult to get. (Prototypes are sometimes difficult to build prior to having automated processes in place.) Or the case when the project manager wishes to share all prototypes with customers or other parties. Further, I counseled designers to also avoid mixing common environmental test samples with those for EMC tests. (Such as temperature/humidity.) The concern to me was the potential for a latent failure to bias the results of another test phenomena. On this point the most experienced engineers tended to agree, not wishing to fix a problem any more complex than mere EMC failures alone. My paranoia can run deep though, and just considering that prototypes are often assembled/placed by hand lowers my confidence that each EMC or safety sample represents production. The answer here is (when possible) keeping the prototype secured for future comparison, and conducting audits of production samples. My experience in this area was with commercial test and measurement/control equipment, largely card level and portable mains powered systems, under ENs 61326 for EMC with 61010-1 (UL 31X1) for safety. Best Regards, Eric Lifsey At 11:48 AM -0500 3/29/04, FastWave wrote: >Fellow Compliance Engineers, > >[...] would you recommend that safety certification/testing be >done before or after EMC testing? The key issue being whether a "fix" for >one discipline will require a re-test for the other discipline. > >[...] > >Bill Bisenius >E.D.& D. >bi...@productsafet.com <mailto:bi...@productsafet.com> > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
