HTC CE-8201, Manual, Page: 16 / 19

- 15 -
R1, R2,...RN are the grounding resistances of N grounding bodies we require.
R1T, R2T,...RNT are the resistances measured on each grounding branch with clamp meter.
This is a nonlinear equation system with N unknowns and N equations. It has a definite solution,
but it is very difficult to solve it manually, even impossible when N is large. To this end, please
purchase our company’s limited point grounding system solution program software, and users
can use office computers or laptop computers for machine solution. In principle, in addition to
ignoring the mutual resistance, this method does not have the measurement error caused by
ignoring R0. However, the user needs to pay attention to: In your grounding system, if there are
several grounding bodies connected to each other, you must measure the same number of test
values for the program to solve, not more or less. The program also outputs the same number of
ground resistance values
2
!
Single point grounding system
From the principle of testing, the clamp meter can only measure loop resistance, but cannot
measure single-point grounding. However, users can use a test wire and a ground electrode near
the grounding system to artificially create a loop for testing. The following introduces two methods
for measuring single-point grounding with a clamp meter. This method can be applied to
occasions where the traditional voltage-current method cannot be tested.
⑴ !
Two-point method
As shown in the figure below, find an independent grounding body RB with good grounding
near the tested grounding body RA (such as nearby water pipes, buildings, etc.). Connect RA and
RB with a test wire.
Because the resistance measured by the clamp meter is the series value of two grounding
resistances and the resistance of the test line.
RT=RA+RB+RL
RT is the resistance measured by the clamp meter.
RL is the resistance of the test line
Therefore, if the measured value of the clamp meter is less than the allowable value of
grounding resistance, then the grounding resistance of the two grounding bodies is qualified.
⑵ ! Three-point method
As shown in the figure below, find two independent grounding bodies RB and RC near the
tested grounding body RA.
The first step is to connect RA and RB with a test line, as shown in the figure below. Use the
clamp meter to read the first data R1.
NT
N
N
R
R R R
R
=
+ + +
+
-
) 1 ( 2 1
1
......
1 1
1