Research and Design of Two-wire Capacitive Liquid-position Sensor

Capacitance sensor is widely used in liquid-position measurement,and calibration of sensors on-site is necessary in practical application,for the changes of mediums and measurement range.To simplify the calibration method,this paper designed a digital liquid-position sensor,it used the PIC16F683 MCU as the core.The sensor adopted two methods in calibration,analog method and digital method.Analog calibration was taken to make sure the range of measurement before leaving the factory.Digital calibration was used when the sensor was to be installed on-site.The actual measurements of two liquid-position values with differences between them,were taken to correct the zero point and the times of magnification,and the precision of the liquid-position sensors was ensured.The structure of two-wire output of 4 mA to 20 mA electric current by using the AD421 MCU is convenient to coordinate with currently existing instruments or microcomputer system.