Operation; Measurement Principle - VOLTCRAFT EMZ-1000 Bedienungsanleitung

7. Operation

Never exceed the maximum permitted input values. Never touch circuits or parts of
circuits when they may contain voltages greater than 33 V/ACrms or 70 V/DC! Fatal
hazard!
Make sure the contact surfaces of the clamp are kept clean and do not use caustic
detergents or harsh cleaning aids for cleaning.
Hard collision between the jaws must be avoided when opening and closing the
clamp. This can cause damage to the measuring coils.
It is normal for the clamping jaws to produce a slight buzzing noise during resistance
measurement. Make sure you are familiar with that noise to be able to discern from
the alarm tones.
Always observe the measurement range and the operating environmental conditions
specified for this tester.
a) Measurement principle
The tester's basic principle for ground re-
sistance measurement is the loop resist-
ance measurement. See sketch. The fold-
able current clamp of the tester consists of
a voltage coil and a current coil. The volt-
age coil sends the excitation signal and
induces a "U" potential in the circuit under
test. An "I" current is generated in the cir-
cuit under test under the effect of the "U"
potential. The tester measures "U" and "I"
and uses the formula shown to obtain the
measured resistance "R".
36
EMZ-1000
U
R = U / I