The Study On Measurement System Of Capacitive Displacement Sensor

In the field of engineering surveying,displacement measurement is an important research subject.Various measuring instruments used in different situations have been born since ancient times.Since modern times,as a branch of displacement measurement,the precise displacement measurement got deep probe and close attention of national scientific research institutions and equipment production companies by the level of the science technology and manufacturing improving.As a common micro displacement measuring tool,the capacitive sensor with simple structure,high precision,high sensitivity and good dynamic performance,have a wide range of applications in industrial production,aerospace and automobile industry and other industries.However,there are many defects in the capacitive displacement sensor,such as small output signal,to be affected by environmental temperature easily and parasitic capacitance.Intelligent sensor technology as a kind of emerging technology based on traditional sensors in the information processing,realizes high precision data collection,information processing through the effective combination between the sensor and microcomputer.In this paper,the measurement system of capacitive displacement sensor is analyzed and researched,and the measurement of capacitive displacement sensor is built,and the sensor optimization is carried out by using the intelligent sensor technology.The following research contents are mainly completed:?1?To research the principle of capacitive sensor.Comparing with dielectric variable type,area variable type,pole variable type,and considering the practical application,so the paper used differential variable area capacitive sensor to measure displacement.?2?In view of the error caused by environmental factors and additional capacitance,analyzing from the material selection,the paper choose the copper and nickel chromium alloy with low temperature coefficient and encapsulate external devices to reduce the influence of humidity and electromagnetic interference.Improving the initial capacitance between the plates was used to reduce the edge effect.The driver shielded cable technology was used to reduce the parasitic capacitance due to the error.?3?In order to reduce the influence of temperature factor on the capacitive displacement sensor further,the sensor must be compensated for temperature.The temperature calibration experiments was carried out.Through the data fusion technology,the paper compared different algorithms performing the sensor temperature compensation,got the compensated fuctional relation between the sensor output voltage and the displacement,reduced the influence of temperature on the sensor.The algorithm uses multiple regression equation method,traditional BP neural network and BP neural network based on bayesian regularized l-m algorithm.BP neural network based on bayesian regularized l-m algorithm was the best,and the temperature sensitivity coefficient was optimized from3.811×10^-2/°C to 1.703×10^-3/°C,and the temperature additional error dropped from 77.5%to 6.81%.?4?With STM32 MCU as the core,the function relation is saved in the microcomputer.We establish the intelligent sensor system with capacitive displacement sensor and microcomputer combined.The function is the signal acquisition of capacitive displacement sensor and temperature sensor,data processing,wireless transmission and the transmission of data to the LCD display.The interior includes dc voltage regulator,signal acquisition module,CAV414 signal conditioning module,alarm module,LCD1602 display module,button module,nRF24L01 wireless transmission module and RS232 serial communication module.On the basis of the hardware circuit,IAR EWARM is applied to design the corresponding software program to ensure the regular operation of the system.Finally through the debugging,this system can effectively complete the optimization of capacitive displacement sensor system with the ability of a certain distance and wireless transmission capacity,stable running,and certain application value in the measurement of short distance displacement.