Research On Key Technology Of Unipolar High Frequency Response Capacitive Displacement Sensor

In the modern manufacturing processing field, study on non-contact dynamic measurement has extensive and important applications, such as Capacitive displacement sensor has good dynamic performance, high resolution, simple structure, is very suitable for high precision dynamic, noncontact measurement. But the capacitive displacement sensor in parasitic capacitance and the distributed capacitance sensor probe under the influence of edge effect is significant and effective capacitance is often submerged, the problems are more prominent in the dynamic. So to solve these two problems existed in application of capacitance sensor, a high precision dynamic key the test of capacitive displacement sensor.The paper of research on key technologies of unipolar high frequency response capacitive displacement sensor is aiming at the two key problems existing in current capacitance sensor research. The main method is to use mathematical modeling theory and simulation design of capacitive sensor with two layers of shielding protection, and the basis of the existing capacitive displacement sensor modulation circuit. Composite phase compensation approach is proposed, improve the current modulation circuit detection capacitance and anti-interference ability; finally aiming at the problems of the capacitance sensor circuit temperature drift in high designed travel fractional rectifier circuit and multiple feedback filter, as part of the sensor signal detection. The main research is as follows:1.An in-depth analysis on the main method of the current operational amplifier am capacitive displacement sensor. On the basis of comprehensive comparison, the subject designed the composite dynamic compensation modulation circuit and combined with the fully actuated cable technology, consist of the sensor signal modulation part of the subject, through the simulation analysis, this paper proves that the design is reasonable.2.The sensor circuit generally exist of many separation of components and the operational amplifier, usually affected by the common mode interference, including the temperature drift, the parasitic capacitance and 50 Hz signal. There is the half wave rectifier circuit and instrument amplifier circuit for a differential full wave rectifier circuit, and combined with the corresponding notch filtering and multi feedback low-pass filter circuit, to meet the requirements of the sensor signal detection part3.In depth study of the design method of capacitive displacement sensor. Thethree pole probe design and combined with the sensor sensitivity, range of measurement. By the ideal parallel capacitor and equation of the edge effects, this paper established mathematical model of the probe. And by simulation analysis verify error influence of the capacitor sensor.4.The design of the sensor shield structure, complete the carrier signal program and the realization of sensor data acquisition.5. Sensor displacement experiment platform is set up to test the capacitance sensor probe and sensor.Static experiments show that the sensor in the measurement range of 0mm~1mm resolution up to 30 nm, half an hour show stable value is 100 nm. Dynamic experiments verify the sensor circuit with 13 k Hz frequency response.