This has come up everywhere I've worked. In order to adequately test for vulnerability, logically, one has to apply a discharge during each of the operating conditions an equipment might take. Given the number of different logical states a microprocessor-controlled EUT might use, this could take forever! From the standpoint of doing a conscientious test, it would be desirable to test MORE often than once per second.
But because the real-world ESD event is an isolated one, repeated discharges are not a realistic test. Also, many devices incorporate built-in ESD protection using protective parts of limited dissipation, and it is possible testing TOO often will destroy the protection circuit. Once per second turns out to be a compromise, and one which may be followed without being too persnickety. What about a longer interval? Sure -- provided we test all of the logic states that might be latched up by the discharge! Ten discharges per point, plus and minus, at each of the voltage levels prescribed, will probably turn up enough of them to pin down a susceptible device no matter WHAT the interval is. One hour? Well, if you can afford to do thirty hours of test, you can do three points at ONE voltage level. One minute? Still takes a long time. And let's face it; this is mind-numbing work. So one second seems to ME to be just about right. Let the poor tech -- or the poor engineer! -- take a break once in a while! I'll add that there may be failure modes that take longer than one second to show up. You want to do the test in such a way that the tester can note and adjust to this; I once tested something that had a 30 second delay before a failure showed up. This can't be helped, and, in this particular case, one second is far too often. Cortland Richmond ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ 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: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net 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.rcic.com/ click on "Virtual Conference Hall,"
