Resistance tester is widely used in various fields, such as the measurement of the coil resistance of motors and transformers, the contact resistance of switch terminals and cable sockets, and the contact resistance of high-power electrical switches. These resistors are generally at the MΩ level or even the μΩ level, which requires high measurement accuracy. Therefore, the industrial design of the resistance tester needs to meet the requirements of high precision, high stability, easy operation and portability.