The basic principle of ETCR series clamp-type grounding resistance meter to measure grounding resistance is to measure loop resistance.Earth Resistance Tester The jaw part of the clamp meter is composed of voltage coil and current coil. The voltage coil provides an excitation signal and induces a potential E on the circuit under test.Earth Resistance Tester Under the action of electric potential E,Earth Resistance Tester current I will be generated in the measured circuit.Earth Resistance Tester The clamp meter measures E and I,Earth Resistance Tester and the measured resistance R can be obtained by the following formula.

Principle of current measurement:Earth Resistance Tester The basic principle of C+ clamp-on earth resistance meter to measure current is the same as that of current transformer. The AC current I of the measured wire generates an induced current I1 through the current magnetic ring and current coil of the jaw.Earth Resistance Tester The clamp meter measures I1 and the measured current I can be obtained by the following formula. Middle: n is the coefficient of transformation of Earth Resistance Tester the secondary and primary coils.