Nick: I have a folder of grounding info which will have some test results. I'll figure out a way to get it to you. In the meantime you might want to google for "Rudy Severns grounding". He's N6LF if I recall correctly. Some of his test results appeared in QEX and also were presented at Dayton a few years ago. Chuck > Date: Wed, 18 Jul 2007 04:45:29 +0000> To: [email protected]> From: > [EMAIL PROTECTED]> Subject: Re: [IRCA] Measuring "AC resistance" of ground > rods to earth> > At 21:04 17/07/2007, you wrote:> > > -------------- Original > message ----------------------> >From: Nick Hall-Patch <[EMAIL PROTECTED]>> > >. Most of the traditional> > > methods use power line frequencies; however, > I've used the three> > > point method using an AC generator at various > frequencies up to 5> > > MHz, and ended up getting really confused with the > results> > > (decreasing conductivity with frequency....). Ran out of time, > and> > > never went back to it.> > >> >Nick> >> >Did you mean decreasing > conductivity with increasing frequency? If > >so, that's the way it's > supposed to work. Otherwise, something > >weird happened if conductivity > decreased at lower frequencies.> > Umm, bad phrasing there on my part, which > implied the measurement of > ground conductivity.> > If I recall correctly, > what the three! point method measures is the > resistance between a ground rod and the earth, and with more > conductive soil, that resistance would be lower. Conductivity and > resistance are DC measurements, and the results using the three point > method and a DC source were about as expected (multiple rods gave a > low resistance, a single 8" rod gave high resistance)> > Using AC you'd actually be measuring impedance I would guess. I > believe there's capacitive reactance in parallel with that resistance > between the rod and the earth, and I'd expect that reactance to > become lower as the frequency went up, and the overall impedance would drop.> > Instead, I saw the "impedance" from rod to earth go up with > increasing frequency, so I must be misunderstanding something, or > calculating incorrectly.> > If you know of any published results for a test like this, please > refer me to it, so I can see where things went wrong (if they > did). Now to find the spare time to follow up on it.! > > best wishes,> > Nick> > > > > > __________________________________ _____________> IRCA mailing list> [email protected]> http://montreal.kotalampi.com/mailman/listinfo/irca> > Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers> > For more information: http://www.ircaonline.org> > To Post a message: [email protected]> _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca
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