Dear Group, For most EUTs there is no need to do lower level testing in contact mode ESD. The time is better spend (meaning a better test results uncertainty is achieved) if the number of discharges is increased at the highest test level (hundreds is a good number). Although it is possible that a system fails at e.g., 2 kV contact mode (e.g., incomplete reset) and passes at 4 kV contact mode (full self-recovering quick reset) the likelyhood of that happening is not that large to require it in a standard.
For air discharge lower level testing is needed, as the risetime is often much lower at lower voltages. Of course, if no discharge occurs, no further testing at even lower levels makes sense. I do know that what I am saying violates the present IEC 61000-4-2 standard. ut it reflects the coming version of IEC 61000-4-2. The standard does not intend to protect agains every possible ESD failure. I would like to receive your input, as I am one of the US-representatives in IEC TC77b WG-9 (ESD). David Pommerenke -----Original Message----- From: Neil Helsby [mailto:nei...@solid-state-logic.com] Sent: Monday, June 10, 2002 4:56 AM To: emc-p...@majordomo.ieee.org Cc: kro...@yahoo.com Subject: Re: IEC 61000-4-2 ESD & 61000-4-5 Surge lower levels I think there are two points here. 1) If you believe that in the environment in which it will be used, your product may be subject to levels in excess of that defined in the standard, you must test to that higher level. 2) Yes, failures can occur at mid range levels. We have just recently experienced this problem with ESD. Below about 3.5 kV and above about 4.5 kV the product worked fine. But at 4 kV we experienced a failure mode. If we had only tested at 8 kV we would have missed the problem. I also had a problem some years ago with mains voltage dips to 0V. Having a test set that enabled the period to be varied in ms increments, I discovered a problem affecting a voltage regulator. When the mains dip was between about 16 ms and 35 ms, the regulator went into a bistable mode switching on then off at each pulse. Outside these periods, it worked satisfactorily, eventually losing output when the period was extended. The problem with investigating these types of failure is determining the size of step between measurements. Too short a step and you will be testing forever, too long and you could miss a narrow band of problem. Regards, Neil Helsby ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.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: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- 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: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
