Digital Ground Resistance Tester Model 4500
33
Where: A = distance between the electrodes in centimeters
B = electrode depth in centimeters
If A > 20 B, the formula becomes:
ρ
= 2
π
AR (with A in cm)
ρ
= 191.5 AR (with A in feet)
ρ
= Soil resistivity (ohm-cm)
This value is the average resistivity of the ground at a depth equivalent to
the distance “A” between two electrodes.
Z
Y
X
X
v
BATTERY
CHARGE
BLINKING DISPLAY
AND
POINTER INDICATE
EXCESSIVE
- TRANSIENT NOISE
- ELECTRODE
RESISTANCE
EXTERNAL BATTERY
12 V
TEST
RANGE
TEST CURRENT
mA
2 10 50
Ω
κΩ
2
20 200 2 20
50/60/400 Hz_110V
b<1a
20
a
a
a
Z electrode
Y electrode
Xv electrode
X electrode
DIGITAL GROUND
RESISTANCE
TESTER
MODEL 4500
Figure 18
4.9
Soil Resistivity Measurement Procedure
(4-Point)
Given a sizeable tract of land in which to determine the optimum soil resis-
tivity, some intuition is in order. Assuming that the objective is low resis
-
tivity, preference should be given to an area containing moist loam as
opposed to a dry sandy area. Consideration must also be given to the
depth at which resistivity is required.
