Principle Of Operation - Megger DET10C User Manual

Megger Download Manager features:
1. Single step data download from the DET20C in CSV format
2. Files managed using standard Windows™ format
3. Powerful CSV Viewer included to view, sort, edit, graph and print downloaded data.
4. Compact driver files for quick and easy disk and internet updates
5. Full help facility
NOTE: For operation of the Megger Download Manager refer to the help menu included in the
software.
NOTE: Selecting the DET20C driver, then clicking the "Download" button on the tool bar gives the
procedure for data download from the instrument

PRINCIPLE OF OPERATION

Below is a simplified typical ground distribution system. The equivalent circuit is shown in Figure A.
If R , R , R , ... R
1 2 3
If a constant voltage is applied to the circuit, the following equation is true.
Where
If R and R , R , ... R
g 1 2
much less than R
Example:
If R and R , R , ... R
g 1 2
In this example, we can see that as long as the number of multiple electrodes is large enough, the
equivalent resistance is negligible with respect to the ground resistance to be measured.
11
are simplified to R
n eq
V = R + R
g
I
Req= 1
( S
)
1
Ri
are similar values, and n is a large number (such as 200), then R
n
and approaches zero.
g
are all 10 Ω, respectively and n = 200. Then R
n
R =
eq
1
10
V = R + R
g eq
I
, then only R and R
g eq
eq
i = 1, 2, ......, n
R >> R (Req
g eq
1
+ 1 + ... + 1
10 10
=10 + 0.05 =10.05 Ω
are left in the circuit (refer to Figure B).
0)
by calculation equals
eq
= 0.05Ω
a R
a
will be
eq