This paper describes the design, simulation, processing and test result of a high sensitivity accelerometer based on the piezoresistive effect which uses an overlay bridge detection method. The structure of this accelerometer is supersymmetric ＂mass-beams＂. This accelerometer has 8 beams, where two varistors are put in the two ends. Four varistors compose a Wheatstone bridge and the output voltages of the 4 Wheatstone bridges have been superimposed as the final output voltage. The sensitivity of the accelerometer can be improved effectively by these clever methods. A simplified mathematical model has been created to analyze the mechanical properties of the sensor, then the finite element modeling and simulation have been used to verify the feasibility of the accelerometer. The results show that the sensitivity of the accelerometer is 1.1381 mV/g, which is about four times larger than that of the single bridge accelerometers and series bridge sensor. The bandwidth is 0-1000 Hz which is equal to that of the single bridge accelerometers and the series bridge sensor. The comparison reveals that the new overlay detection bridge method can improve the sensitivity of the sensor in the same bandwidth. Meanwhile, this method provides an effective method to improve the sensitivity of piezoresistive sensors.
With the springing up of the MEMS industry,research on accelerometers is focused on miniaturization, integration,high reliability,and high resolution,and shares extensive application prospects in military and civil fields.Comparing with the traditional single cantilever beam structure or ＂cantilever-mass＂ structure,the proposed structure of ＂8-beams/mass＂ with its varistor completely symmetric distribution in micro-silicon piezoresistive triaxial accelerometer in this paper has a higher axial sensitivity and smaller cross-axis sensitivity.Adopting ANSYS, the process of structural analysis and the manufacturing flow of sensing unit are showed.In dynamic testing conditions, it can be concluded that the axial sensitivity of x,y,and z are Sx-48μV/g,Sy = 54μV/g and Sz = 217μV/g respectively,and the nonlinearities are 0.4%,0.6%and 0.4%.
