6.3
Earth Resistance Measurement
(four-wire method in line with the
Wenner principle and only possible with the accessory set, order number:1048!)
Measurements in dangerous proximity to electrical systems should only be carried
out in conjunction with clear instructions from a responsible electrical specialist and
must not be carried out alone.
For a preliminary calculation of the diffusion resistance of a ground, the specific earth
resistance must be known. The resistance may not be read directly. The value displayed
must be included in a formula and then calculated.
4
Insert the four earth rods in a
line ensuring each rod is the same
distance apart . The earth rods
may be inserted by maximum
1/20 of distance" a" into the earth.
4
Clamp the four clamps H, S, ES, E
to the probes, as described in
figure 6.3.
4
Turn the rotary switch (13)
to the 4 pole position.
4
Set contact voltage (11).
4
Set automatic (16) or manual (12)
frequency selection.
4
Press key "Start" (14).
4
Read the resistance value.
The specific earth resistance is calculated as follows:
ρ
e = 2
π
x a x RE
The specific earth resistance is sub-
ject to large fluctuations depending
on a number of factors: humidity
and temperature are of extreme
importance. For observations
during one year, the fluctuations
may be compared to a sinus curve
(see figure 6.3.1).
Also refer to display indications in chapter 7.0
22
6.3
a
a
a
H
S
ES
E
Variations in the specifie earth resistance
ρ,
during
the course of a year.
6.3.1
