Principle Of Measurement - Chauvin Arnoux C.A 6410 Notice De Fonctionnement

PRINCIPLE OF MEASUREMENT

The diagram below of the principle of measurement illustrates the general case of
measurement of a loop resistance consisting of:
- the ground rod Rx
- the Earth
- n ground rods
- a guard wire looping together all these earths
- The generating winding of the clamp develops an AC voltage with a constant
level E.
- The current measurement winding in the clamp has the value I = E/R
Knowing E set by the generator and I measured, we can deduce R
(value displayed on the clamp).
- More generally, this principle makes it possible to find defective earths. In fact, the
loop resistance is composed of:
R (value to be found)
x
(value normally very low less than 1 Ω).
R
earth
R // R ...// R (negligeable value: case for multiple parallel earths).
1 2 n
(value normally very low, less than 1 Ω).
R
guard wire
R = Rx + R + (R
loop earth
By approximation, R
loop
If this value is very high, an inspection of this earth rod is strongly recommended.
I
M
E
Rx
R earth
// R ...// R ) + R
1 2 n guard wire
= Rx.
Guard wire
33
loop
loop
R1 R2 Rn