Research On MEMS Multi Pressure Sensor Test System

During the development of MEMS capacitive pressure sensor,the optimization of design parameters requires characterization test.Therefore,it is necessary to design a test system to fill the gap between sensor development and sensor calibration.This paper took the MEMS capacitive absolute pressure sensor and MEMS capacitive differential pressure sensor designed by the research group as the samples.The software and hardware design of the test system were discussed.The main contents of this paper are as follows:1.Schemes for pressure control.Different schemes were designed according to the principle of absolute pressure sensor and differential pressure sensor.The pressure range required for absolute pressure sensor test is about 0~120kPa.In order to improve the efficiency and reduce the error,a fuzzy PID controller was designed.The NI MyDAQ controlled by the computer acquired the reference pressure and output PWM signal.The automatic control of pressure was realized by the high frequency solenoid valve.The results of pressure continuous control show that,when the interval is 10 kPa,the adjustment time ? 3.4s,and the steady-state error is within ± 0.2kPa.The pressure difference required for differential pressure sensor test is about-60~60Pa.The micro pressure pump was used to control the pressure difference between the container and barometric pressure.The pressure of the container would sudden change when the solenoid valve open.2.Data acquisition and management.The GPIB toolkit of LabVIEW was used to realize the bidirectional communication between computer and LCR.During the test,proper pressure was provided and the data was acquired by LCR as required.The connection between MySQL and LabVIEW was realized by LabSQL toolkit.Two data query modes were designed: simple query and SQL query.Data preview was realized by fitting specific data with least square method.3.Design of micro capacitance detection system.The LCR is unsuitable for the application research of the MEMS sensor,it is necessary to design a micro capacitance detection system with small size and high-accuracy.The hardware mainly included PCap01 capacitance digital conversion circuit and STM32 minimum system;the software was composed of the MCU program and LabVIEW program.Under the condition that the capacitance to be measured is very similar to the reference capacitance,after filtering,the sampling rate of the micro capacitance detection system can reach 18 Hz,the standard deviation is 0.40 fF,the nonlinearity error is 3.97%,the relative error is 1.86%.