Design And Implementation Of Capacitive Level Measurement System

There are many kinds of sensor types which can measure the level in real time.The advantage of the capacitive level sensor is that the structure is simple and easy to install.The maintenance cost is low and the electrode material is stable,it can resistance high temperature,low temperature and high pressure corrosion.The sensor has high sensitivity and high sensitivity Precision and other advantages.So it is widely used in small and medium scale measurement systems.But the traditional capacitive sensor is susceptible to stray capacitance and easily interference from the external environment,what may cause the capacitance is not accurate and thus affect the accuracy of the entire system.And when the traditional capacitive sensor is replacement of the measurement medium,it need to re-calibration and calibration,so it is not convenient in the practical use.In the face of the above situation,it is urgent to design a level measuring system suitable for use in complex industrial environments.In this paper,we design a capacitive level measurement system which is based on PCap01-AD and STM32L152.According to the principle that the capacitance value changes with the height of the medium between the plates,achieve the goal of the real-time measurement of the height of the liquid level or material level.At the same time through the reasonable data processing algorithm to achieve a stable output of the data.In the aspect of material selection of the capacitive sensor,the cylindrical inner electrode is made of polytetrafluoroethylene(PTEF),thus can make the sensor more stable.And the use of coaxial shield and other measures to reduce the external environment interference on the capacitance measurement,making the capacitance measurement data more stable and accurate.In the structure of capacitive sensor,two kinds of sensors are designed:single-stage structure and multi-stage structure.In the hardware circuit using a special circuit design techniques to greatly increase the system's ability to resist electromagnetic interference and has the function of anti-surge and anti-reverse.In the aspect of software algorithm,the initialization and register configuration of STM32L152 is completed according to the characteristics of PCap01-AD.The special data processing algorithms are designed for different application environments and the capacitive structure.The system carried out a long-term test in test platform and the user site,the result shows that no matter in what environment,it can operation stably and has good accuracy and linearity.