By hvhipot 
The loop resistance tester uses a high-reliability high-power integrated circuit, which is composed of a DC constant current series resonance, a preamplifier, an A/D converter, and an indicating device. As shown in the figure below, it has milliohms and microohms. The low-value resistance measuring instrument with a wide range is easy to operate, and the test current can be automatically stabilized to ensure the stability and reliability of the data.
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 terminal buttons of the measured resistance, and the sampling circuit collects the simulation of the current flowing through the measured resistance to generate a voltage drop. After the signal is amplified by the preamplifier, the analog signal is converted into a digital signal by the A/D converter, and then the data is filtered, calculated, and processed by the microprocessor. The ratio of the voltage drop U to the current in the loop gives the DC resistance value of the measured body;
Since the loop resistance tester works under high current conditions, in order to eliminate lead resistance and improve measurement accuracy, a fHV Hipot Electric Co., Ltd.-wire connection measurement method is adopted. At the same time, in order to avoid overheating, the current duration is required to be short, and a firm and reliable current connection should be used. According to the requirements of the regulations, the detection points are uniformly selected. When the loop resistance tester outputs current, compare the output value of the loop resistance tester with the digital display reading of the DC high-power series resonance standard resistor, which can maximize the measurement Accuracy.