Hi John, et al, It's true that much ISM-type equipment is used in "controlled environments", but I've easily measured greater than 4kV in our R&D lab area here in Colorado. It -is- rare, though that it will get over 8 kV.
I also agree with your other point. After spending 21 years qualifying digitizing scopes for EMC/ESD, I can tell you that every time we develop a faster front-end, the measured ESD risetimes seems to get faster and faster! I've taken our 12 GHz model (Agilent) and measured ESD risetimes as fast as 20 ps from shaking a plastic bowl of Hershey Kisses! Air discharge is much slower and varies considerably with approach angle and speed. Contact discharge is more consistent with ps edges. Yet the standard specifies the typical ESD HBM risetime as 1 ns. This is a good case where the measurement technology at the time limited the standards. For more on the measurement and validation of ESD, you should be able to find a presentation Greg Senko (president of Teseq, ex-Schaffner EMC) and I did via a Google search. Regards, Ken Wyatt Technical Services, LLC 56 Aspen Dr. Woodland Park, CO 80863 Email: [email protected] Web: www.emc-seminars.com LinkedIn: http://www.linkedin.com/in/kennethwyatt (719) 310-5418 On Jun 8, 2009, at 10:47 PM, John Woodgate wrote: > I suspect that most equipment to which IEC 61326 applies AND is > exposed to ESD is used in air-conditioned spaces where humidity is > kept at medium values and ESD voltages do not reach extreme values. > > There is a further issue. Until recently, the methods of verifying > the output of ESD test hand-pieces were subject to considerable > doubt and much controversy. To check the output waveform, > oscilloscope bandwidths of at least 6 GHz are required, and these > were very rare. So a lot of historical data were collected using > test equipment whose characteristics are subject to significant > uncertainty. - 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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html 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]>
