Design, Fabrication and Test of a Low Range Capacitive Accelerometer with Anti-Overload Characteristics

Capacitive accelerometers have been widely used in the fields of mobile phones, automobiles, seismic monitoring and others because of its high sensitivity, good repeatability and high precision. This type of accelerometer usually has a low range. The sensitive structure of the sensor is too vulnerable to damage in high impact environments, so it basically has no ability to detect smaller signals after a relatively high acceleration. This paper presents a capacitive accelerometer which employs a four-terminal fixed structure. Acceleration is outputted by a differential capacitance formed between the mass and the upper and lower glass plates. With consideration of better anti-overload capability and small signal detection capability, structure optimization and anti-overload protection such as chamfer and protection measures have been carried out. According to the simulation results of the optimized structure by finite element analysis software, it has a maximum stress of 62 Mpa when a 20,000g shock is load, the maximum displacement within effective range (100g) is 13.7μm , and it also has a first-order frequency response of 7.477 kHz. And then, the process flow is designed and the device is fabricated. Static capacitance test and flip test are utilized to verify its static performance. The anti-overload capability of the device is tested and verified by Marshall Hammer impact experiments.