Study Of A Capacitive Power Material Level Sensor

With the continuous improvement of China’s industrial automation level, The requirements of monitoring on the material level is higher and higher in industrial production; Switch mode material level monitoring are mostly used at present, product which can be continuous monitoring is not much; According to theory of capacitive sensor, the paper study and design a kind of capacitive material level sensor for powder material.According to the characteristics of the powder materials, this paper determines the mechanical structure of a double plate and provides the various parameters of the mechanical structure; Tiny capacitance detection is a difficulty for capacitive material level sensor, hardware circuit using discrete component is designed for small capacitance detection, this hardware circuit is more complex and the accuracy is not guaranteed, So, for small capacitance detection the paper used the integrated circuit AD7746, it can convert the output capacitance analog to digital quantity, and the precision is very high.The paper also designed the hardware circuit of capacitive material level sensor, including the power supply and capacitance measurement circuit; The capacitance measurement circuit used STM32chip as the main control chip which own Rich peripheral interfaces, and485serial port which has advantages of long transmission distance and strong anti-jamming capability communicate with PC.A double plates are homemade device structure, and has set up a platform test to test the performance of the sensor device; At the same level height many experimental data was collected, the stability of the sensor device is4.21%from calculating the collected data; The sensitivity is0.35pF/cm using the sensitivity calculation formula; The linearity is±3.64%using The least square method to fit a straight line using the collected data; Sensor repeatability is1.99%through repeating the experiment many times.The results show that the double plate structure of capacitive material level sensor performance is good, it can meet the requirements of general industrial production for the material level monitoring, and has extensive application value.