If I were doing this, I'd start by doing some research, probably start with the web -- you could also go to the ESDA web site and see what they have -- they've got a number of people that worry about the possibility of charges in different factory environments where semiconductor devices are handled.... As for how much charge a person could hold,,, most models use 100pF to about 330pF -- a few use bigger numbers, but IEC uses 150pF and the automotive people use up to 330pF.... V = q/C and q is highly dependent on the triboelectric charging -- leather soles on shoes vs nylon carpet, for example, or in yur case maby leather soles vs steel PLUS how much contact, how long, etc..... THEN I think it becomes a question of the bodies ability to HOLD a charge in a given environment.... Not so much a question of charging..... Too many variables to come up with a single number, so I'd go back to experimenting with real people.. Some years ago at a trade show, we set up an experiment where people would stand on a rubber mat and we'd charge them up with an ESD simulator to 5kV -- they would then discharge into a small target assembly through a key or other metal object held in their hand..... The results were all over the map -- positive and negative, current levels that varied by an order of magnitude..... Point being,,,, it'll be tough to pin down what would happen doing this experiment in a high humidity area -- Probably still get quite a range of results, but I'm really leaning toward the idea that it isn't a matter of how much you can charge up someone in high humidity, but more a matter of whether the person retains the charge in high humidity --
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: Thursday, April 15, 2004 11:10 AM To: drcuthb...@micron.com; 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
