Brain, I like to repeat: For "verification" you do not need calibrated equipment or full bandwidth. The "verification" is just a method to increase trust in the calibration. If you use some homemade current target and a 500 MHz scope, you will get a pretty good picture of the waveform and detect most changes in an ESD generator.
A comb-generator run on an OATS is not a NSA calibration, still it establishes trust in the antennas, cables and the spectrum analyzer. David Pommerenke University Missouri Rolla From: brian_ku...@leco.com [mailto:brian_ku...@leco.com] Sent: Monday, May 05, 2003 1:04 PM To: emc-p...@ieee.org Subject: Re:ESD gun verification John, First I would like to say how impressed I am with Jim for building his own target. Reading through his detailed description of all he went through made me think the $2000 is well worth it. I wish I had the skill and resources to do stuff like that. Years ago we used to just air discharge our ESD gun to make sure it was working ok. We never performed a "verification" test. This we thought was covered by the annual calibration and assumed that the ESD gun was designed solid enough to not have to worry about it. It wasn't until some of these Laboratory Accreditation organizations got popular that daily "verification" of your ESD gun required the verification of the current waveform. This makes a fairly inexpensive test very expensive for most labs. In addition to the $5000-$8000 for the ESD gun, now you have to have the equipment to do "verification". For us this was a $2000 target, a faraday cage, and a $20,000 1Ghz bandwidth digital storage scope. If you are testing everyday your very expensive scope is for the most part dedicated for this purpose. You can use cheaper scopes, but it has to have a high bandwidth and storage capabilities. A huge investment no doubt if you want to do it right. BTW, don't you also have to verify your scope is working correctly? Hmmm. The other issue is with the time involved with performing the verification test. To look at all the details of the current waveform for just a few voltages both positive and negative polarity plus the time to document and keep records of it takes time many customers don't want to pay for. Somehow you have to work in the cost because time is money and someone has to pay for it. To test every voltage level and polarity can take more time than the ESD test itself. So a happy reasonable medium has to be found. In a perfect world someone would invent a little box I can discharge my ESD gun into and a little green light would come on to tell me it is operating OK. If someone could invent such a box and keep it inexpensive, I would buy one. Of course it would probably cost a fortune to get the box calibrated and how do I verify the box is working correctly? Hmmm. Brian ____________________Reply Separator____________________ Subject: ESD gun verification Author: jde...@nas.com List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: 5/05/03 12:02 PM John: I faced the same problem about six years ago. I needed to do "verification" in between the expensive annual "calibrations". I first explored the option of buying a Pelligrini Target. As I recall, the quotes I received were around $2000. That seemed outrageous, so I decided to build one myself. I'll bet it took me at least 3 days to make sense of those goofy mechanical drawings in 61000-4-2. If only they had included a photograph or good cross-section in the Standard! Anyway, I finally figured it out, translated the drawings into something understandable by a U.S. machine shop, and got all the brass parts fabricated locally. It took several in-process consulting sessions with the machinist, but I finally got all the brass parts done for around $300. Then, I purchased a $25 silver electroplating kit. It was like Science Fair time in my workshop! Some hours of painstaking soldering later, the target was completed. I mounted it over a specially-drilled hole in the brass wall panel of our anechoic chamber (you need a Faraday Cage of some sort, and this seemed the easiest). I did a quick check using our Tektronix 1 GHz analog oscilloscope ... and the risetimes and overall waveforms measured within spec! Then, I sent the target to Haefely-Trench for a "calibration" (against their standard Pelligrini target). The results were very, very close. Having performed many verifications at this point, my advice (if you want fairly accurate and repeatable results): 1. Make (or buy) something resembling the 61000-4-2 target. 2. Use a Faraday Cage. 3. Be aware how important the POSITION of the ESD Gun Grounding Strap is to these measurements ... especially to risetime measurements. I always take a photograph of the setup, including the "shape" of the Grounding Strap and where it is attached. If you don't do this, you'll get pretty wild variability between verifications. 4. Even a 500 MHz oscilloscope would probably be OK for "verification". Just make certain that all setup parameters (including Ground Strap placement) are EXACTLY the same each time. That way, if the GUN happens to change, you'll at least know what to do next. Give me a call if you'd like a photo. Good luck! Jim Ericson Quality System Manager/Sr. EMC Engineer Acme Testing Company Acme, WA. 888-226-3837 j...@acmetesting.com ----- Original Message ----- From: "John Harrington" <jharring...@f2labs.com> To: <emc-p...@majordomo.ieee.org> Sent: Thursday, May 01, 2003 11:45 AM Subject: ESD gun verification > > Hello All > > Does any one have a quick and dirty (and hopefully cheap) way to verify the > performance of an ESD gun. > > Please, no one suggest building the current sensing system described in the > back of IEC 61000-4-2. I don't understand the drawings let alone have the > workshop or materials to consider it. Although, I may pay someone to build > it for me... > > I am desperate enough to consider buying something off the shelf (if I could > find said shelf). > > All help appreciated > > John Harrington > EMC Technical Manager > F-Squared Laboratories > > ------------------------------------------- > 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 > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > 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 Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
