Application of parallel capacitor for force transferring in resonant micro accelerometer

Abstract

The characteristics of force transferring in parallel capacitor is presented, the external force applied on one plate can be transferred to another with a reverse direction and changed magnitude by coupling effect of mechanical domain and electric domain. The main principle of such behaviors is analyzed, and the relation of input and output is calculated by analytic method, it is indicated that the changed quantity is dependent on the ratio of electrostatic stiffness and mechanical stiffness. The application of this behavior in resonant micro accelerometer is then presented, the parallel capacitor is used as a leverage to transfer the external inertial force into the axial force of librating beam to change the natural frequency of resonator, so the acceleration applied can be measured by measuring the shift of frequency, finally, the structure of sensor is fabricated by Deep Reaction Ion Etching(DRIE) and silicon bonding technologies, and the test indicates the sensitivity of accelerometer is related to different voltage applied on capacitor.

Effects of dielectric charging on the output voltage of a capacitive accelerometer

“…Several studies have been conducted on the design of MEMS capacitive accelerometers [19,20].Fringe field and the thickness effect of the electrodes is discussed in [21][22][23] to provide a better parallel plate capacitor model for the accelerometer. Open and closed-loop accelerometer system model is discussed in [24][25][26][27] and better performance such as borader measurement range is demonstrated in the closed-loop accelerometer system.…”