"Do you use a earth tester? Which brand do you know is very good and
accurate to consider?"
Jorge,
If you can, try and find a "clamp-on" earth tester rather than the type that
relies on the fall-of-potential method with electrodes. There are several
good clamp-on units by Megger, Fluke and AEMC. I recently acquired an AEMC
model 3711. It wasn't supplied with a calibration loop, but I found one
from Fluke that quickly checks calibration at 100, 50, 12.5, and 0.5 ohms.
You'll want that calibration loop to validate the accuracy of the clamp
tester, especially if you use an off-brand model from Asia.
N4CC and I recently installed a large grounding field, with some ground rods
driven down to a depth of 24 ft. The clamp-on device was useful for quick
validation. Had we used a unit with electrodes, it would have taken us much
longer to perform our tests. By the way, in sandy/clay type soil here in
north FL, we found that connecting 8 ft. rods end-to-end to form a 24 ft rod
substantially lowered earth resistance by a factor of 10x.
Paul, W9AC
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