>>On the other hand very low voltage (and energy) events, such as jingling >>change have very high di/dt because of the tens of ps risetimes that >>occur at low voltage.
I think this is why, as I recall, some (maybe all?) IEC standards require you to test not only to the ESD level indicated, but also the lower levels too. For example, if you are required to test at level 4, you are also required test at levels 3, 2 and 1. This is counter-intuitive -- "Surely the highest voltage is the worst case?" -- but apparently grounded in good physics, which Doug explains better than I would. PS: As to testing at higher levels than typical IEC values, I have read that the human body can, rarely, gain a charge of up to about 30kV(??), in conditions of low RH. Others may have better insight into this. Also, some manufacturers may want to build some "margin" into their test results: if five samples pass at 8kV, how sure can you be that the next 995 production units would also pass? PPS: I have a question of my own, drifting off topic slightly: if the relative humidity was fairly high when you passed the ESD test, and you retest (esp. air discharge?, or indirect discharge?) some months later when humidity is lower, could the same EUT now fail? (I think the answer is, yes?) Best Regards, Glyn Glyn R. Garside (mailto:ggars...@us.tuv.com) Senior Engineer, Industrial Machinery Division TUV Rheinland of North America, Inc. (Chicago Office) 1945 Techny Rd, Unit 4, NORTHBROOK, IL 60062-5357, USA http://www.us.tuv.com ------------------------------------------- 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,"
