HT instruments T2100 - Manual (Page 14)

T2000-T2100
EN – 13
(B) Measuring the earth resistance of a rod with the 3-point method
In this situation, at an appropriate distance from the rod being tested with RA resistance,
there are two independent auxiliary rods with resistance RB and RC, having optimal
features in terms of earthing (e.g.: metal pipe, reinforced concrete building, etc…),
whose
value can be compared to the value of RA.
As a first measurement (see Fig. 11), connect the RA rod to the RB rod and use the
instrument to measure the value of resistance R1.
Fig. 11: Three-point method: first test R1
As a second measurement (see Fig. 12), connect the RB rod to the RC rod and use the
instrument to measure the value of resistance R2.
Fig. 12: Three-point method: second test R2
As a third measurement (see Fig. 13), connect the RC rod to the RA rod and use the
instrument to measure the value of resistance R3.