HT instruments T2100 - Manual (Page 10)

T2000-T2100
EN – 9
4.5. RESISTANCE MEASUREMENT
CAUTION
Measurements carried out by the instrument can be used to evaluate single
rods’ resistance values within an earth installation without disconnecting the
rods,
assuming they do not affect each other.
4.5.1. Operating principle
The principle upon which the test carried out by the instrument is based is the “resistive loop
resistance measurement”, as shown in Fig. 6: Measurement of loop resistance
.
Fig. 6: Measurement of loop resistance
The inner part of the instrument is made of 2 jaws, one for current and one for voltage. The
voltage jaws generate a potential (E) on the loop during resistance (R) measurement. A
current (I) is consequently generated on the loop and is measured by the current jaws.
Based on the value of parameters E and I, the instrument displays the resistance R value
calculated as a ratio:
R =
I
E