Small resistance can be seen everywhere in various electrical equipment, such as the contact resistance of equipment such as power cables, communication cables, circuit breakers, relays, motors and transformers. These resistances are quite small and can reach the order of milliohms, which is not easy Measurements, combined with changes in temperature, also affect the resistance of the resistor. When the measurement time is too long and the power supply is too long, it may cause the measured resistance value to be higher with the increase of temperature. These situations may cause a large deviation in practical applications, which affects the measurement result. Measurement is a common subject in electronic measurement, it has very important significance. In engineering practice, it is often necessary to determine the resistivity of certain high-conductivity materials. In scientific research, resistivity measurement is also often used as a means to monitor changes in the structure and state of materials.

In the power system, the transformer can increase or decrease the voltage of the generator, so that the transformer becomes the leading power generation, transformation, transmission, and power supply industries, so the transformer is one of the most important equipment in the power system. The operation of the transformer The state is related to the safe and reliable operation of the power system. The transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the iron core (magnetic core). Due to the special inductance, the winding resistance measurement becomes the transformer in the handover, overhaul and change tap The routine test project that is essential after the switch, whether it is performed in the transformer production process, maintenance process or accident analysis site, is an important means to ensure the production quality, maintenance quality and safe operation of the transformer, and it is also after the failure Important test items.