In article
,
Toom Tabard wrote:
What I don't understand is how to find impedance down earth pipe and
at socket with a multimeter.

In practice, you can't. You need a proper tester which just looks a bit
like a multi-meter. It puts a very large load to earth on the circuit for
a fraction of a second and measures the current flow, and from that
calculates the impedance.
They are quite expensive devices and need regular calibration.

--
*What happens when none of your bees wax? *

Dave Plowman London SW
To e-mail, change noise into sound.