The Automatic Control And Testing For Micro Gas Pressure Sensor Testing System

With the rapid development of micro-machining technology and MEMS technology, gas pressure sensors based on micro-hotplate became a hot topic at home and abroad due to their many advantages, such as small size, low power, wide measuring range, fast response, easy integration with IC etc. The static and dynamic performance testing for sensor are needed to evaluate the comprehensive performance. So a vacuum automatic control testing system which provides various and necessary environment for pressure sensors is built up.This paper introduces working principle and the basic characteristics of the gas pressure sensor with micro-hotplate, analyses the characteristics of vacuum control and testing, determines control strategy for testing system. The structure of hardware and software and human-machine interface about control system is further introduced in this paper at the same time. Focus on the control method and theory of the vacuum control system, fuzzy control theory is applied and simulated with MATLAB. A fuzzy controller is designed, and an automatic testing control system is established, which provides a good platform for the performance testing of the sensor.Fuzzy PID control algorithm is applied to the testing control system, one D/A card is used to control two mass flow controller. When the pressure is higher than 1kPa in vacuum chamber, the mass flow controller with large flux is used to realize pressure control. When the pressure is under lkPa, the mass flow controller with small flux is used. The gas pressure sensor with micro-hotplate is placed in the vacuum, the computer collects the real-time responded signal through A/D card, compares response signal to the gas pressure signal in the vacuum chamber, analyzes the sensor's performance sequentially.Experiment showed that the system can control the gas pressure real-time with middle vacuum in vacuum chamber, ensure gas pressure or gas flow controlled and provide a dynamic gas pressure environment for aptitude testing and reliable experimental data for the gas pressure sensor with micro-hotplate.