Design of a high precision automatic resistance measuring instrument

In modern times, we usually use digital multimeter to measure the value of resistance, but when using multimeter to measure resistance, we need to shift gears manually. On the other hand, when we measure the resistance with unknown resistance value, we must adjust the test range of the multimeter several times before we can determine the resistance value. This results in long test time and low test efficiency. In order to overcome this shortcoming, this paper designs a resistance testing device that can automatically adjust the measuring range, which can automatically screen the measuring range, saving the testing time and improving the testing efficiency. The device uses the STM32 chip as its core controller. The instrument includes a core control circuit, an A/D conversion circuit, a range switching circuit, a display circuit, and a test circuit. The constant current method is used to generate multiple constant current outputs, and the function of automatic resistance measurement is achieved by switching the relay to get different range. The instrument can measure the resistance of 0 similar to 1M, which has a good use value.