Design And Realization Of Control Circuit Of Gas Calibration Device

Gas calibration device plays an extremely important role in laboratory gas analysis,environmental pollutant monitoring,instrument calibration and other fields,and its accuracy is the premise to ensure its wide application.In order to improve the accuracy of concentration,the technology of mass flow control,high-precision voltage acquisition technology and the technology of ADRC are the key technical approaches to design the control circuit of the gas calibration device.By comparing many gas distribution schemes of standard gas,this paper designs a dynamic real-time gas distribution scheme based on mass flow controller(MFC),moreover,the standard gas can be continuously configured,the gas distribution accuracy is high,the dilution ratio can be adjusted dynamically and is not affected by temperature and pressure.The designed gas calibration device control circuit has many functions,and realizes the high-precision configuration of standard gas concentration,high-precision acquisition and precise control of the temperature of the chassis and air chamber,and the data corresponding to the temperature are stored in the FLASH chip and calculate the actual temperature of the chassis and the air chamber through the serial communication module,as well as many other functions.According to the design requirements,the hardware control circuit of the gas calibration device is expounded.Design of temperature acquisition circuit using ?-? ADC improves the accuracy of temperature acquisition.Using TEC as temperature control element,the design cost is reduced and the operation steps are simplified.The automatic disturbance rejection control algorithm is used to accurately control the temperature of the chassis and the pneumatic circuit,so as to achieve the set temperature.Good control effect of the control circuit is achieved by the main controller GD32.The performance index of the control circuit of the gas calibration device was tested by constructing an experimental test platform.The actual measurement results show that the level conversion function of the designed control circuit of the gas calibration device is normal,the temperature resolution can reach 0.05?,and the temperature accuracy is0.67%FS.It is found that the repeatability error of the temperature sensor PT100 is 0.13%,which meets the requirements of the design index,verifying the feasibility and validity of the design scheme of the control circuit of the gas calibration device.