The loop resistance tester, also known as the transformer loop resistance tester, is mainly used to test the contact resistance of the static and dynamic contacts of the high-voltage circuit breaker. The conductive loop resistance of the circuit breaker mainly depends on the contact resistance of the static and dynamic contacts. The existence of the contact resistance increases The loss of the conductor during energization increases the temperature of the contact. Its value directly affects the current-carrying capacity during normal operation, and to a certain extent the short-circuit current cut-off capacity, which is also an important data reflecting the quality of installation and maintenance . The loop resistance tester is suitable for high- and low-voltage switch contact (loop) resistance, high-precision measurement of the DC resistance of cable lines, and it is also suitable for other occasions that require large current and micro-resistance measurement. It has a very extensive role in the power testing industry. 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 DC 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 the measurement results are calculated manually, and there are certain errors.

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 microcomputers, which greatly reduces the work.