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