The Study Of Smart Measuring System For DC Resistance Box

At present, the DC resistance box measuring work is still in the stage of manual testing, process cumbersome, time-consuming, error prone. In order to save human resources, improve the efficiency of resistance box test, on the basis of JJG 982-2003 "verification regulation of DC resistance box", this paper designs and tests a smart measuring system for DC resistance box.This paper designs a new intelligent bridge based on wheastone bridge resistance detection principle. Program-controlled voltage module with constant output replacing the adjustable resistance, digital millivoltmeter replacing the mechanical null indicator, the bridge balance can be composed by micro control chip instead of manual, making calibration automatic. In addition, in order to realize the automatic verification, this paper designes a resistance box ratio switching module using the stepping motor as executing mechanism. Rigid connecting the rotor of stepping motor with the resistor ratio knob by the cutting sleeve, the pulse signal issued by the micro control chip controls therotor turning a predetermined angle, at the same time driving the knob with it, thereby completing the resistance gear adjustment.The smart measuring system consists of host computer and slave computer. They communicats by the ethernet interface. Host computer is mainly responsible for the crew sent instructions, receiving the lower position machine data, calculation and processing test results and export, print excel test report task; resistance measurement function and resistance switching function is completed by the slave computer. The slave computer uses the STM32F103C8T6 produced by STMicroelectronics as the control core. The slave computer consists of main control module, the intelligent bridge module, millivolt meter module, resistance automatic switching module, power supply module. The DC sampling part uses the median average filtering and the least square method fits the calibration curve, removalling interference. Designing the fuzzy controller to the step size of the adjust the voltage module, making the adjustment of bridge balance process rapid and accurate.This paper describes the theoretical basis of the system and the design method of software and hardware, and tests the system function. The test shows that, the verification system designed in this paper can meet the requirements of JJG 982-2003 "verification regulation of DC resistance box", has the value of popularization, with reference to the precise measurement of the similar resistance value.