Many high-current electrical equipment in the power system need to accurately measure the resistance of the loop in preventive tests and handover tests. Therefore, the loop resistance tester is widely used in electrical testing. Next, I will introduce you to the working principle of the loop resistance tester.

1. Design of loop resistance tester

The loop resistance tester uses a highly reliable high-power integrated circuit, which is composed of a DC constant current source, a preamplifier, an A/D converter, and an indicating device. As shown in Figure 1, it has milliohms and microohms. The low-value resistance measuring instrument with a wide range is easy to operate. It can measure loop resistance, wire resistance, coil resistance, etc. with one key, and the test current can be automatically stabilized, ensuring the stability and reliability of the test data.

2. Measurement of loop resistance tester

When the loop resistance tester is measuring, the high-frequency switching power supply outputs a current of 100A or more, which is applied between the two end buttons of the measured resistance, and the sampling circuit collects the simulation of the voltage drop caused by the current flowing through the measured resistance After the signal is amplified by the pre-amplifier, the analog signal is converted into a digital signal by the A/D converter, and then the data is filtered and arithmetic processed by the microprocessor. According to the principle of equal currents in the series circuit, the Ohm's law R= U/I is the ratio of the voltage drop U at both ends of the load and the current in the loop to get the DC resistance value of the measured body.