HT instruments M71 - Manual (Page 25)

M71
EN – 24
8.2. EARTH RESISTANCE MEASUREMENT, VOLT AMPERE METRIC METHOD
Method for small sized earth rods
Let current stream between the earth rod and a current probe placed at a distance equal to
fivefold the diagonal of the area limiting the earth installation. Place the voltage probe at
approximately half way between the earth rod and the current probe, finally measure
voltage between both of them.
Fig. 7: Measurement of earth resistance for small sized earth rods
Use several rods in parallel
and moisten the surrouding
ground if the instrument
does not manage to supply
the current necessary to
perform the test due to a
high ground resistivity.