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VIII Measurement Principles
1 Resistance Measurement Principle
Basic principle of the clamp-on ground
resistance meter in measuring the ground
resistance is measuring the loop
resistance (detailed in appendix).
Refer to the following picture; clamp jaw
of the clamp is composed of voltage coil
and current coil. The meter measures E
and I, and know the measured resistance
R by the following formula.
R=E/I
2 Current Measurement Principle
The basic principle of UT278A clamp-on ground resistance meter is the same with
that of current transformer measurement.
The AC current I of the measured wire, passing through the current magnetic ring
and current coil on the clamp jaw, produce the induction current I1 which could
be measured by the clamp meter and know the measured current I by the
following formula:
UT276A/278A OPERATING MANUALUT276A/278A OPERATING MANUAL
Conductor being measured
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