Measuring the effectiveness of a ground rod involves finding out what its
connectivity to a place called "Remote Earth" is. You do not measure ground
values at DC. Too many stray amps of DC floating around in the earth. You
use a test set that sends out a know AC freq. at a known current to a remote
ground probe. You then take another ground probe and profile the voltage in
the ground at ten foot intervals (or more, depending) from the ground rod or
field you are concerned about.
When the current/voltage calc. levels off at a certain distance, you assume
you have reached remote earth and use that value for your ground field
contact resistance.
Eric, K6GV
edwoods@pacbell.com
----------
From: ehayes
To: towertalk
Subject: [TowerTalk] Re: Ground Rods & Ohms
To: <towertalk@contesting.com>
Date: Wednesday, April 16, 1997 8:53AM
A short time ago someone indicated they had measured the resistance
on their ground rods. How does one do this? Can it be done with
something as simple as a digital volt meter? What two points do
you measure between? I don't live in a particularly sandy area but
have no idea if my ground rods (6) will actually help if lightning
should visit.
Thanks,
73 Wayne AJ5M ehayes@vnet.ibm.com
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