Design Of Automatic Calibration System Of High Voltage And High Resistance Box

High voltage and high resistance box is also known as DC high-voltage and high-valueresistor,megger standard resistor,etc..,and it is a standard device for calibrating megohm meter,insulation resistance tester(digital megohm meter)and high insulation resistance meter(high resistance meter).High-voltage and high-resistance box is equipped at all levels of metering,military industry,scientific research institutes,industrial and mining enterprises,with a large number.At present,in the process of calibration of high-voltage and high-resistance box,it needs manual calibration by point,tedious operation,and it is time-consuming and easy to make mistakes.Therefore,it is imperative to design an automatic calibration system.Based on the present calibration situation and development trend of high-voltage and high-resistance box,in this paper,the relevant principles and their advantages and disadvantages were analyzed,and a set of automatic calibration system of high—voltage and high-resistance box was designed.The system was composed of host(high-voltage and high-resistance calibration device),upper computer and printer.The host's calibration on high-voltage and high-resistance box could be carried out alone,and also could be carried out after the combination with the upper computer.The hardware part of the host circuit consists of four parts,which are adjustable DC voltage source,precision voltage circuit,precision current measurement circuit and control circuit.DC voltage is supplied by DC voltage source,and signals high-voltage and high-resistance box were obtained through precision voltage circuit and precision current circuit.Then the sampling and A/D conversion of the detected signals were realized through the hardware system with the single-chip microcomputer as the core,and finally the measured value was displayed on the LCD screen.Upper machine software module was composed of basic information settings module,data acquisition and processing module,receiving and saving module,display module,generating records and certificate module and communication module.The software system could realize the initialization of each module and measuring circuit,and complete the type-in of basic information(Model,production unit,range,inspection unit,etc..)of high-voltage and high-resistance box to be measured,measured resistance value sampling,data processing,display and generation of certificate/reports.After completing the hardware and software intermodulation of the system and confirming that the planned design function can be realized,the detailed test experimental study was conducted.According to the planned uncertain evaluating scheme "A" and "B",the experimental data were processed and analyzed with comparative transmission method.The study showed that the measurement performance of the automatic calibration system was stable and reliable,with high work efficiency,and it was very suitable for automatic verification and calibration of the high-voltage and high-resistance box.