The advantages of this measurement method are more intuitive and convenient. The disadvantage is that the current passing through the switch during measurement is very small, which can not damage the oxide film on the contact surface, thus causing a large error (too large). Therefore, this method is not recommended in the loop resistance measurement of high-voltage switch.

Indirect measurement by voltage drop method (voltammetry):

The voltage drop method is to measure the voltage drop (mV) between the inlet and outlet terminals of the switch socket with a millivoltmeter when the DC current of the switch socket is applied, and then calculate the main circuit resistance of the switch socket with Ohm's law.

Measuring circuit with transformer and silicon rectifier. At the same time, when measuring the resistance of the main circuit with the voltage drop method, the current passing through the test object is large enough to damage the metal oxide film on the contact surface, reducing the measurement error, and the measured value is relatively accurate. Therefore, the voltage drop method is recommended for the measurement of the main circuit of the switch socket.