AG4QC wrote:

I was wondering if anyone built some sort of ground resistance tester? I
read that the NEC requires 25 Ohms or less.. But I don't understand how to
measure that. I certainly could use a ohm meter between a ground rod and the
test subject, but then the ground rod I use as a reference could be faulty..
It seems to me it must be measured in some other manner. Maybe low frequency
signal and then measure how much it's absorbed in the earth?.. I know they
sell a clamp on ground resistance tester for big bucks. Considering it's a
clamp on, it certainly don't have any external reference.. Anyway, I was
wondering if anyone had any experience with these testers and maybe building
one?

Joe AG4QC




I think others have touched on the key requirement of testing at least
three grounds rods. Then
from the three (or more) readings you can determine each resistance
value. As others have pointed out
you probably need a high current to mask the other currents in the soil.

Cheers.
Bill K7NOM