Amprobe DM-111S Current-Data-Logger - Manual (Page 43)

DMIIIS
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11. MEASURING PROCEDURES
11.1. HINTS FOR FLEXIBLE CLAMPS USE
All flexible clamps are based on Rogowski's coil principle:
dt
di
M V
coil
 
which shows that the voltage output signal is proportional to the rate of change of current.
In order to get current value, the voltage output signal is integrated electronically.
Typically the voltage output signal is really low and this suggests using shielded cable for
coil connection to instrument's inputs.
WARNING
As the Coil Output connector can't be perfectly shielded it's
recommended to outdistance it by any Potential source.