The loop resistance tester is made using digital circuit technology and switch circuit technology. It is a special device for measuring contact resistance and loop resistance of switch control equipment. The electrical circuit resistance of the circuit breaker mainly depends on the contact resistance of the moving and static contacts. The existence of contact resistance increases the loss of the conductor when it is energized, and increases the temperature of the contact. Its value directly affects the current carrying during normal operation. Ability, to a certain extent, affects the ability to cut short-circuit current, and is also an important data reflecting the quality of installation and maintenance work.
There are three main test methods for the loop resistance tester, 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 the contact, that is, 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 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 microcomputer, which greatly reduces the workload.