Do you get the same effect with the coins in a cloth bag or a paper bag? Has anybody tried it? Lou
At 10:57 AM 3/15/99 -0600, you wrote: >Douglas, > >I have seen similar events in a different way. Years ago, I helped design >an electronic system using plastic chassis with nickel surface plating. The >system passed 15kv ESD air discharge and 8kv contact. But in the hardware >lab, the system gets data error everytime a piece of metal (like a screw >driver) is striked against the nickel plated surface on chassis. A digital >scope is used to measure the noise generated on power and ground planes on >the PCB inside the chassis and the scope captured a noise voltage as high as >8 volts peak to peak on the PCB from a few hundred MHz to beyond GHz. The >PCB was very well decoupled with power next to ground planes and many on >board capacitors. This puzzled me at first. But I remembered a very >knowledgeable mechanical engineer once told me to never use nickel material >in an application where friction takes place. Nickel has a very hard and >rough surface, so in a frictional application, it always damages the mating >surface. Maybe this explains the events that you saw, and the ESD generated >by the metal surface was much higher than 15kv. > > >Regards, > >George Tang > > > >Douglas McKean wrote: > >> Hans, >> >> That's certainly an interesting explanation, but does >> not correlate to at least three different scenarios. >> >> 1) A calibrated ESD simulator in self discharge >> mode at 15KV. When the results of the ESD >> simulator are compared to the results of the >> coins, the coins have a fairly wideband constant >> level from 0 - 2 GHz. Both start off at roughly >> the same level with the only the coins remaining >> constant throughout. The ESD simulator has approx >> a -20dB per octave drop off. >> >> A side interest is that on the display of the SA has >> an IF overload indication. This tells me that the >> transients from the coins are quite possibly a lot >> higher and much quicker than what the SA can handle >> within the sampling window. >> >> 2) The level from the coins is proportional to the >> dissimilarity of the metals of the coins. A bag of >> quarters has a lower profile than a bag of quarters >> and pennies. Thus, there is some function due to >> electronegativity differentials. Actually, a >> significant amount of difference. >> >> 3) I can cause the same effect by sliding the coins >> back and forth as a group within the bag. Thus, >> the coins are in at least incidental contact with >> each other so that differing potentials amongst >> the coins is minor. >> >> I'm not sure if anyone knows the reason. >> >> Regards, Doug McKean >> >> At 11:11 AM 3/11/99 -0800, Hans Mellberg wrote: >> > >> > >> >There is an expanation for this seemingly unlikely event. >> > >> >Having coins in a baggie and jingeling them causes the following >> >events to occur: >> > >> >The rubbing of a coin against the polymer causes triboelectric >> >charging of both the coin and localized areas of the bag. Since there >> >are multiple coins, each coin will charge at some voltage level but >> >not necessarily the same as another coin. When two coins of different >> >charged voltages come within dielectric breakdown distances, a >> >discharge will occur from one coin to the other in order to equalize >> >the charge distribution (q1=C1V1 and q2=C2V2. When they touch, the new >> >q1 will be C1V3 and q2= C2V3 where V3=(q1+q2)/(C1+C2)). Since coins >> >are electrically small with very small capacitances, the expected >> >discharge waveform has a very fast risetime hence the radiation at the >> >GHz region. There will also be discharges from the localized charged >> >areas of the polymer to coins of different voltages. While separating >> >two charged surfaces from each other, the voltage rises significantly >> >since the capacitance is being reduced and the conservation of charge >> >must be preserved which is the basis for tribolectric voltage >> >generation. >> >Hope that helps >> >Hans Mellberg >> > >> > >> >---b...@namg.us.anritsu.com wrote: >> >> >> >> Hi Douglas, >> >> >> >> What you described is very interesting! But I cannot understand >> >"Jingling >> >> change in a ziplock bag produces very high levels of super fast >> >transients >> >> up into the GHz range." It seems to me that jingling coins, jangling >> >keys, >> >> and slamming metal door would certainly produce acoustic waves. How >> >come >> >> they also produced electromagnetic waves? If do, under what >> >conditions? >> >> What is the mechanism to produce "very high level" of transient EM >> >waves? >> >> Did that company incorporate those kinds of "Jingling change in a >> >ziplock >> >> bag" tests into regular ESD tests for their thereafter products? >> >What is >> >> the lessen we all should learn from this particular example? >> >> >> >> Hopefully you don't think it's offensive to ask above questions. I >> >am just >> >> very curious. >> >> >> >> Thank you. >> >> Best Regards, >> >> Barry Ma >> >> (408)778-2000 x 4465 >> >> >> >> ------------- >> >> Original Text >> >> From: "Douglas McKean" <dmck...@corp.auspex.com>, on 3/10/99 2:55 PM: >> >> At 08:03 AM 3/8/99 PST, Bailin Ma wrote: >> >> >Hi Group, >> >> > >> >> >We have already seen awards for the most misleading ads, worst >> >attire, >> >> >worst films, ..... >> >> >Why not awards for worst EMC and PS qualities? >> >> > >> >> >Barry Ma >> >> >Morgan Hill, CA 95037 >> >> >> >> >> >> Long ago in another company, I was completing the testing >> >> for a large rack mounted device, i.e. emissions, immunity, >> >> safety, some parts of Bellcore. We got a call from one >> >> of our customers complaining about how sensitive our equipment >> >> was and how susceptible it was to ESD events during their own >> >> testing of our equipment. This was deemed unacceptable by them. >> >> This decision of theirs jeopardized a sale of several million >> >> dollars. The finger was duly pointed by everyone right to yours >> >> truly. My head was literally in no uncertain terms put on the block. >> >> >> >> I contested producing repeatable and acceptable ESD test results >> >> that were BELOW the BER levels specified by Bellcore with ESD test >> >> levels ABOVE that specified by the test standard. I wanted as much >> >> margin as possible for our product. >> >> >> >> Well, it ended up that if you stood three to four feet in front of >> >> the rack and jingled change in your pocket or jangled a set of keys >> >> in front of it, the product would RESET. Jingling change in a >> >ziplock >> >> bag produces very high levels of super fast transients up into the >> >GHz >> >> range. Worse, slamming the metal door to the lab in which the >> >equipment >> >> was setup would also reset the product. The lab door was say 20 or >> >so >> >> feet from our equipment under test. It took six months of a redesign >> >> cycle to straighten out that one, but it was finally done. >> >> >> >> I always wanted to find out who in God's name could have come >> >> up with such an insidious ESD test by simply putting some change >> >> in a zip lock bag and jingling it in front of equipment. >> >> But, I figured "he", whoever he was, was lost in time. >> >> >> >> And wouldn't you know it? ... >> >> >> >> I now work for that man. >> >> >> >> >> >> --------- >> >> This message is coming from the emc-pstc discussion list. >> >> To cancel your subscription, send mail to majord...@ieee.org >> >> with the single line: "unsubscribe emc-pstc" (without the >> >> quotes). For help, send mail to ed.pr...@cubic.com, >> >> j...@gwmail.monarch.com, ri...@sdd.hp.com, or >> >> roger.volgst...@compaq.com (the list administrators). >> >> >> >> >> >> >> >> --------- >> >> This message is coming from the emc-pstc discussion list. >> >> To cancel your subscription, send mail to majord...@ieee.org >> >> with the single line: "unsubscribe emc-pstc" (without the >> >> quotes). For help, send mail to ed.pr...@cubic.com, >> >> j...@gwmail.monarch.com, ri...@sdd.hp.com, or >> >> roger.volgst...@compaq.com (the list administrators). >> >> >> >> >> > >> >_________________________________________________________ >> >DO YOU YAHOO!? >> >Get your free @yahoo.com address at http://mail.yahoo.com >> > >> > >> >--------- >> >This message is coming from the emc-pstc discussion list. >> >To cancel your subscription, send mail to majord...@ieee.org >> >with the single line: "unsubscribe emc-pstc" (without the >> >quotes). For help, send mail to ed.pr...@cubic.com, >> >j...@gwmail.monarch.com, ri...@sdd.hp.com, or >> >roger.volgst...@compaq.com (the list administrators). >> > >> > >> > >> >> --------- >> This message is coming from the emc-pstc discussion list. >> To cancel your subscription, send mail to majord...@ieee.org >> with the single line: "unsubscribe emc-pstc" (without the >> quotes). For help, send mail to ed.pr...@cubic.com, >> j...@gwmail.monarch.com, ri...@sdd.hp.com, or >> roger.volgst...@compaq.com (the list administrators). > > > > >--------- >This message is coming from the emc-pstc discussion list. >To cancel your subscription, send mail to majord...@ieee.org >with the single line: "unsubscribe emc-pstc" (without the >quotes). For help, send mail to ed.pr...@cubic.com, >j...@gwmail.monarch.com, ri...@sdd.hp.com, or >roger.volgst...@compaq.com (the list administrators). > --------- This message is coming from the emc-pstc discussion list. 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