26
Digital Ground Resistance Tester Model 4500
X-Y Distance
Resistance
Reading Variation
Effective Resistance
Areas (Overlapping)
X
Y' Y Y''
Z
Figure 10
On the other hand, if the auxiliary potential rod Y is located outside of
the effective resistance areas, as Y is moved back and forth the reading
variation is minimal. The readings taken should be relatively close to each
other, and are the best values for the resistance to ground of the ground X.
The readings should be plotted to ensure that they lie in a “plateau” region
as shown in Figure 11.
X-Y Distance
Resistance
Reading Variation
Effective Resistance
Areas (No Overlap)
X
Y' Y Y''
Z
Figure 11
4.4
Measuring Resistance of Ground Electrodes
(62% Method)
The 62% method has been adopted after graphical consideration and
after actual test. It is the most accurate method but is limited by the fact
that the ground tested is a single unit. This method applies only when all
three electrodes are in a straight line and the ground is a single electrode,
pipe, or plate, etc., as in Figure 12.
