MI 3290 Earth Analyser
Tests and Measurements
90
11.3.2 Wenner method Measurement
Place the four earth probes on a straight line, at a distance
a
from one another and at a
depth
b < a/20
. Distance
a
must be between 0.1 m and 49.9 m. Connect the cables to the
probes, then to terminals H, S, ES, and E.
E a r t h
H
S
ES
E
MI 3290 Earth Analyser
a
G
V
A
S - probe
ES - probe
E - probe
H - probe
a
a
b
Figure 11.43: Wenner method example
Wenner method with equal distances between test probes:
b <
a
20
𝜌
𝑤𝑒𝑛𝑛𝑒𝑟
= 2 ⋅ 𝜋 ⋅ 𝑎 ⋅ 𝑅
𝑒
= [𝛺𝑚]
where:
R
e
..................................... Measured earth resistance in 4-pole method
a
....................................... Distance between earth probes
b
....................................... Depth of earth probes
π ....................................... Number π is a mathematical constant (3.14159)
