The Study Of Capacitance Sensor Calibration Technology Used Of Mini-displacement

With the development of science and technology, the magnitude which can be measured will be smaller and smaller. The production of nanometer displacement sensor technology has matured gradually,but after analysis the calibration system of linear displacement sensor from domestic and foreign and JJF1305-2011 (The calibration specification of line displacement sensor), there was not issued a set of calibration system which is use the technology of photoelectric technology and specialized for micro displacement sensor. Therefore, my paper is focus on the characteristic of capacitive displacement sensor that the output voltage and current value is too small, the existing calibration process is too complex, design a set of high precision and resolution and practical calibration system, hope to cover the shortage of calibration system of the micro displacement sensor.First of all, introduced the working principle of capacitive displacement sensor,established the mathematical model of the calibration system which is apply the technology of the laser heterodyne measurement and acousto-optic modulation, calculate the formula of displacement,and designed the principle diagram of the calibration system.Secondly, in order to achieve a certain accuracy requirements of the calibration system,designed the frequency stabilization module, chose the acousto-optic modulator, vibrator,power amplifier and photodiode; devise the circuit of the calibration system, and used the software in the computer to comparison the real-time data of the calibration system and the comparison calibration sensor directly. According to the structural characteristics of the capacitive micro displacement sensor, calibrated it's static and dynamic characteristics. In order to realize the high precision of the calibration system , used lock-in amplifier and sampling integration technique to reduce the influence of noise.Finally, according to the relevant regulations of the evaluation and expression of uncertainty in measurement analyzed the uncertainty of the calibration system. Analyzed the sources of uncertainty in the system and used the formula to calculated the standard uncertainty and extended uncertainty, accomplished the uncertainty report of the calibration system.Completed the traceability of the displacement standard value, and proved that the calibration system conformed to the measuring precision, the calibration system is feasible.The experimental results showed that at standard sine signal which the frequency is 1280Hz, the uncertainty of the capacitance micro displacement calibration system can reached 0.05% , use this calibration system to calibrate the capacitance or inductance micro displacement sensor which frequency response between 0?10kHz.