The Research And Realization Of Angle-vibration Sensor Based On Micro Variable Capacitance

Along with the development of MEMS technology, the structure of MEMS capacitive sensor is much simpler and the resolution is higher. It is widely used in the measurements of displacement, vibration, angle, acceleration and others, and the application is gradually expand of pressure, differential pressure, liquid level and ingredients. In the angle vibration measurement, using the differential structure of the MEMS capacitance sensor can be reduced error and increased sensitivity. But by the influence of miniaturization structure, the capacitance of sensor is only several pF, and the amount of capacitance changes would be even smaller. Therefore, a suitable design to detect the micro variable capacitance is needed, and the angle vibration data should be measured.Started from the physics principles of micro variable capacitance, the detection theory of weak signal and the working principle of micro variable capacitance are elaborated in this article, and the implementation of hardware and software is given. The data acquisition circuit is based on periodic DC charge and discharge by MCU, and then the suitable digital signal method is processed to obtain the angle signal and vibration signal. The entire design of angle and vibration sensor based on micro variable capacitance is given in the article.First, the operating principle of micro variable capacitance and the causes of system noise are analyzed. On this basis, the commonly used detection method of micro-capacitive and signal processing algorithm is analyzed and compared, and then the design of the differential capacitance detection circuit and signal processing algorithms is obtained. After contrast verification, this design is effective and feasible to facilitate the achievement.Second, the detection theory is implemented from hardware to software. The technique is based on the DC charge and discharge theory of RC series circuit, and the vibration and angle offset can be detected by MCU system. After the original signal is processed by the appropriate filter, the noise disturbance could be reduced efficiently, and the fundamental component and the high harmonic component would be separated quickly and accurately, then the curve of the vibration and angle offset can be obtained. SJA1000 is used to connect the angle vibration data of the sensor and the system, and integrity function of the sensor is achieved.At last, the performance of the sensor is tested at various kinds of angle vibration situation. After each step of signal processing, the waveform is read, and the post-process effects of the denoising processing module, the angle signal generation module and the vibration signal generation module is intuitively obtained.In this article, the design of the micro-variable MEMS capacitive angle vibration sensor has been detailed introduced, and the hardware circuit design of the sensor and the realization of digital signal processing is illustrated. Experiment results of sample shows that angle detection and vibration detection can be carried out and non-interfering at the same time.