"Ron Hardin" wrote in message
...
John Gilmer wrote:
Before you complete the bonding connection, check the resistance between
your "proper" ground and your re-bar. If you have time on your hands,
drive a second "proper" ground rod (two "proper" grounds rods will meet
NEC
requirements) and measure the various resistances. You may find that
the
re-bar is a better ground than the "proper" ground.

Measure the (AC) voltage difference before you measure the resistance. If
it's
not zero, don't measure the resistance. Two ground rods some distance
apart typically
have a voltage difference between them even if not attached to anything,
but especially
if one is in use and the other isn't.

Well, with a high input impedance voltmeter (like your typical digital
model) it would be unusualy to NOT detect a fraction of a volt difference.

If such things make you nervous, "load" the circuit by putting a 1000 ohm
resistor across the DVM input leads for all measurements. The resistor
should provide enough "load" to significantly reduce the voltage reading to
your comform level. If you have some stray current leakage inside your
house, pull the main breaker during your testing.

The 1000 ohm resistor will change your resistance measurements but your
expected value should be less that 100 ohms (much less with "good" grounds).

But checking the voltage before measuring resistance is, indeed, a good
practice.