There was an interesting article a couple of years back using two HP close field probes in exactly the manner you descibe. They had constructed a nice sturdy jig to consistently position the probes with respect to each other and got very reliable numbers. Good method.
Brent DeWitt Datex-Ohmeda Medical Louisville, CO > -----Original Message----- > From: owner-emc-p...@majordomo.ieee.org > [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Cortland Richmond > Sent: Thursday, April 15, 1999 12:11 AM > To: Richard Haynes; ieee pstc list > Subject: Re: Conductive Paint > > > Some time ago, in a company far away (well, not THAT far away -- grin) I > had to evaluate problems with a nickel painted plastic chassis, and later, > its copper-painted follow-on. I found I could get good correlation with > performance on the OATS by measuring attenuation between a pair of > shielded loops about an inch or so across, separated far enough > to let pass > a painted chassis or test sample. By comparing air (zero), > galvanized iron > (essentially infinite) and the test sample, I could develop a > good idea how > much it would attenuate fields from currents on the PWB close to it, > inside, and the rest of the world. > > In every case, when a deficiency was noted using this method, close > inspection of the subject chassis revealed problems in the paint > application, too thin, too many interruptions (crack) die to chassis > detail, or failure to make sufficient contact with ground bosses pressed > into the chassis. > > Resistance measurements did not always catch the problem, as cracks and > detail problems were paralleled at DC by a sufficient number of other > paths. Thickness problems WERE always caught by resistance measurements, > however. > > Cortland > > ====================== Original Message Follows ==================== > > >> Date: 14-Apr-99 10:00:21 MsgID: 1067-92308 ToID: 72146,373 > From: "Richard Haynes" >INTERNET:vale...@pluto.njcc.com > Subj: Re: Conductive Paint > Chrg: $0.00 Imp: Norm Sens: Std Receipt: No Parts: 1 > > > Hey, > I am just now writing a paper on measurements of several metals and > coatings so I will just summarize some of the results: > System frequency range Ohm/sq > Zn 50 Hz to 3GHz ~0.1 to ~8 > AgCu 50Hz to 3GHz 1 to 7 > (plated Ag onto Copper particles as fillers) > Ni 50 Hz to 3GHz 3 to 27 > (particle fillers) > Cu 50 Hz to 3GHz 1 to 10 > (Metal) > There are several other systems that I have measured. May get to a > publication this year? > Richard Haynes > 609-497-4584 > > P.S. This is a better technique than the Z technique for absolute > measurement that are reproducable. > > -----Original Message----- > From: Douglas McKean <dmck...@corp.auspex.com> > To: emc-p...@ieee.org <emc-p...@ieee.org> > Date: Tuesday, April 13, 1999 9:26 PM > Subject: Re: Conductive Paint > > --------- > 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).
