I guess the key point here is how you charge the person up. If I use a Van de Graf generator or ESD gun, I am bypassing the key question of interest, which is how much charge can a person generate under these conditions. I guess my crude outlook is I want a mechanized foot "scuffer" to simulate the worst a human could do under these circumstances.
From: drcuthb...@micron.com List-Post: emc-pstc@listserv.ieee.org Date: Thu, 15 Apr 2004 09:16:27 -0600 To: <ken.ja...@emccompliance.com>, <george.stu...@watchguard.com>, <michael.hopk...@thermo.com>, <emc-p...@majordomo.ieee.org> Subject: RE: Defining an ESD Threat Ken, sounds good. Here's what I would try: Use a person, a good capacitor, an oscilloscope (preferably battery operated), and a 10 M ohm probe. Measure the C of the person (200 pF or so) and use a plastic dielectric 100 nF capacitor. Charge the person up by whatever means you want and then have them discharge to the capacitor. The voltage is measured on the 'scope. Calculate the original voltage on the person and the charge. Repeat as needed. Ouch. Dave Cuthbert From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Thursday, April 15, 2004 9:10 AM To: drcuthbert; george.stu...@watchguard.com; michael.hopk...@thermo.com; emc-p...@majordomo.ieee.org Subject: Re: Defining an ESD Threat I am willing to let others set the risetime etc. I am mainly interested in determining the total potential and charge associated with a human discharge in this particularly benign environment of high humidity and metallic/concrete flooring. From: drcuthb...@micron.com List-Post: emc-pstc@listserv.ieee.org Date: Thu, 15 Apr 2004 09:04:01 -0600 To: <george.stu...@watchguard.com>, <michael.hopk...@thermo.com>, <ken.ja...@emccompliance.com>, <emc-p...@majordomo.ieee.org> Subject: RE: Defining an ESD Threat You can charge someone up and discharge them into an ESD target. I did this with myself (I don't like going above 10 kV) to develop a better model. A person does not appear as a simple capacitor with one series resistor. More line a transmission line, a capacitor, and a resistor. And if you want to see the real risetime you will need at least a 3 GHz oscilloscope with a 7 GHz preferred. Dave From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of George Stults Sent: Wednesday, April 14, 2004 3:17 PM To: Mike Hopkins; Ken Javor; emc-p...@majordomo.ieee.org Subject: RE: Defining an ESD Threat http://esda.org/esdbasics1.htm and h tp://www.rfcafe.com/references/electrical/triboelectric_series.htm give further details of the effect of distance apart on the triboelectric series chart. From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Mike Hopkins Sent: Wednesday, April 14, 2004 1:24 PM To: 'Ken Javor'; Mike Hopkins; emc-p...@majordomo.ieee.org Subject: RE: Defining an ESD Threat Ah yes, .... things get more complicated as usual... There is something called the Triboelectric series, which gives you some idea of the charging possibilities between materials.... There further apart two materials are in the series, the more charge you get from rubbing them together -- the more you rub, the more you charge... Look at: http://www.school-for-champions.com/science/static_materials.htm for one.... What you really need is an inexpensive charge meter and a volunteer -- see what you can get on a person in various environments as the humidity increase - it would be easy to do and maybe even some fun.... Use a MiniZap to charge 'em up to different voltages (standing on a rubber mat) and have him/her step off and see if the charge stays....(As I think about it, someone's probably already done it, but not sure where to look...) Best Regards, Michael Hopkins Control Technology Division Compliance Test Solutions Thermo Electron Corporation One Lowell Research Center Lowell, MA 01852 Tel: +1 978 275 0800 ext. 334 Mobile: +1 603 765 3736 michael.hopk...@thermo.com One Thermo, committed to integrity, intensity, innovation & involvement From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Wednesday, April 14, 2004 3:33 PM To: Mike Hopkins; emc-p...@majordomo.ieee.org Subject: Re: Defining an ESD Threat That makes sense, but it only addresses half of the ESD environment question, which is how high a potential can something be charged up to, and how long will it hold the charge. The other half of the question is the charge-generating mechanism. If the surfaces one walks on are largely metal or concrete, how does that effect the amount of charge relative to a carpet? And more importantly, whether the charging surface is carpet or concrete or metal, how can one simulate the charging mechanism in a repeatable fashion? How do you build a human body model not in terms of a capacitor and resistor, but in terms of modeling scuffing one's feet and measuring the resultant charge collection? From: Mike Hopkins <michael.hopk...@thermo.com> List-Post: emc-pstc@listserv.ieee.org Date: Wed, 14 Apr 2004 14:18:24 -0400 To: "'Ken Javor'" <ken.ja...@emccompliance.com>, emc-p...@majordomo.ieee.org Subject: RE: Defining an ESD Threat Simple thing to do is take an ESD simulator and try charging some objects in that environment and see if they will hold a charge.... In high humidity, I'd expect charges to bleed off very quickly on most objects, which is why the ESD threat would be low.... In low humidity, of course, the charged surfaces and/or objects would tend to hold a charge... If a person becomes charged due to triboelectric charging walking across a carpet, I don't know that a high humidity prevents charging -- but it will definately bleed a charge off quickly.... Maybe faster than the charging can take place??? None of this is quantitative, of course,,,, Best Regards, Michael Hopkins Control Technology Division Compliance Test Solutions Thermo Electron Corporation One Lowell Research Center Lowell, MA 01852 Tel: +1 978 275 0800 ext. 334 Mobile: +1 603 765 3736 michael.hopk...@thermo.com One Thermo, committed to integrity, intensity, innovation & involvement -----Original Message----- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Wednesday, April 14, 2004 12:04 PM To: emc-p...@majordomo.ieee.org Subject: Defining an ESD Threat Esteemed List Members, I am working a problem where it would be helpful to define an ESD threat level in a particular high humidity, metallic surroundings environment - expectation is that ESD levels would be much lower than typical. I have a very high level concept of how it might be done, some kind of Van de Graf model of a human discharge. Someone somewhere might have done a similar test to arrive at threats for IEC 1000-4-2 or other standards. Any pointers on how to do this? Thank you, Ken Javor ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ 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: emc_p...@symbol.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://www.ieeecommunities.org/emc-pstc
