The loop resistance tester is mainly used to test the contact resistance of the dynamic and static contacts of the high-voltage circuit breaker. The conductive loop resistance of the circuit breaker mainly depends on the contact resistance of the dynamic and static contacts. The existence of the contact resistance increases the loss of the conductor when it is energized. The temperature at the contact point increases, and its value directly affects the current carrying capacity during normal operation. To a certain extent, it affects the ability to cut off short-circuit current and is also an important data reflecting the quality of installation and maintenance work. At present, there are mainly three test methods for loop resistance testers, and the specific operations are as follows:

1. Bridge method: When using a double-arm bridge to measure the resistance of the circuit breaker's conductive loop, it is difficult to eliminate the oxide film with a large resistance because the measurement loop passes a weak current, and the measured resistance value is too large. The current is small, and it is difficult to form contraction at the contact point of its contact, so the contraction resistance cannot be measured.

2. Voltage drop method: When a direct current is applied to the circuit under test, a voltage drop will be generated on the contact resistance of the circuit, the current and voltage values passing through the circuit will be measured, and the contact resistance will be calculated. The test process is cumbersome, and there are certain errors in manual calculation of measurement results.

3. Micro-ohmmeter method (loop resistance tester): The principle is the voltage drop principle, but the measurement and calculation are all processed by single-chip microcomputer, which greatly reduces the workload.