MEMS Capacitive Accelerometer Signal Readout System

MEMS accelerometer is an important inertial measurement device,which has been widely used in var-ious industries.Among them,MEMS capacitive accelerometer has the advantages of high precision,high sensitivity,high dynamic range,which makes it occupy a dominant position in accelerometers.This has at-tracted the attention and research of many scientific research institutions at home and abroad.The capacitive accelerometer is composed of an acceleration sensor and a readout circuit.In order to improve the perfor-mance of the accelerometer,the structure of the acceleration sensor and the readout circuit can be improved.When the structure of the acceleration sensor is determined,the design of the readout circuit determines the overall performance of the accelerometer,so it is particularly important to design a suitable readout circuit.In this paper,a modulation and demodulation type readout circuit is designed for the capacitance ac-celerometer made in our laboratory.At the same time,in order to improve the practicability and convenience of the capacitive accelerometer,this paper also designed a low-latency,high-precision,easy-to-operate,low-cost capacitive accelerometer readout system.The research work mainly includes the following contents:1.Aiming at the self-made capacitance accelerometer in our laboratory,this paper designs a modulation and demodulation type readout circuit,which is composed of a differential amplifier circuit,a bandpass filter circuit,a multiplier demodulation circuit and a low-pass filter circuit.At the same time,this article analyzes the working principle of each module,gives the design process,and optimizes the components selection,parameter setting,PCB board production,etc.2.Aiming at the readout circuit,a MEMS capacitive accelerometer readout system is designed in this paper to realize the functions of voltage signal analog/digital conversion,abnormal value detection and filter-ing,wireless data transmission,numerical value and waveform display.In addition,this paper also uses the voltage-acceleration mapping model based on least squares polynomial fitting and the voltage-acceleration mapping model based on Gaussian process regression to optimize the readout system to improve the test accuracy of the system.3.The performance test of the MEMS capacitive accelerometer and its readout system is carried out according to the relevant test standards.The test results show that the accelerometer system designed in this paper has a zero bias of 126.5m V,a sensitivity of 1518m V/g,a non-linear error of 859.5ppm,and a range of-0.6～0.6g,which meets the requirements of acceleration test.After using the voltage-acceleration map-ping model based on least squares polynomial fitting and the voltage-acceleration mapping model based on Gaussian process regression to optimize the readout system,the average absolute error of acceleration test was reduced from 0.1694m/s~2to 0.1526m/s~2and 0.0770m/s~2,and the maximum error was reduced from0.7609m/s~2to 0.5133m/s~2and 0.3195m/s~2,the overall performance has been effectively improved.