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
1
, R
2
, R
3
, ... R
n
are simplified to R
eq
, then only R
g
and R
eq
are left in the circuit (refer to Figure B).
If a constant voltage is applied to the circuit, the following equation is true.
If R
g
and R
1
, R
2
, ... R
n
are similar values, and n is a large number (such as 200), then R
eq
will be
much less than R
g
and approaches zero.
R
g
>> R
eq
(Req
0)
Example:
If R
g
and R
1
, R
2
, ... R
n
are all 10
Ω
, respectively and n = 200. Then R
eq
by calculation equals
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
V = R
g
+ R
eq
I
Req= 1
(
S
1
)
Ri
i = 1, 2, ......, n
R
eq
=
1
= 0.05
Ω
1
+ 1 + ... + 1
10
10
10
V = R
g
+ R
eq
=10 + 0.05 =10.05
Ω
a
R
a
I
Where
