Principle Of Operation - Extech Instruments 382356 User Manual

Principle of Operation

Typical multi-grounded distribution system.
If the parallel ground resistances,
R , R , R ,etc, up to R
1 2 3
as R , then only R
eq
left in the circuit
If a constant voltage is applied to the circuit, the following equation applies:
V
=
I
If R and R , R , R
g 1 2 3
then R will be much less then R
eq
Example:
If R and R , R , R
g 1 2 3
equals:
Rn
are combined
n
and R are
g eq
+
R R
g eq
...R , are approximately the same, and n is large (200, for example),
n
and may possibly approach zero.
g
...R are all 10Ω respectively and n = 200, then R
n
=
R
eq
1
10
R
2
R
eq
I
V
=
R
where:
eq
∑
1
=
1 1
+ +
...
10 10
7
R
R
1
Rg
1
=
, i 1 2 , ,...
1
R
i
by calculation
eq
Ω
. 0 05
382356 V2.0 5/03
g
n