Increase of Three-Axis Accelerometer Sensitivity Using Capacitor in Spring

This study has introduced a three-axis capacitive accelerometer, in which the part of the capacitor that calculates acceleration is installed in the z direction in the spring to improve the sensitivity in the said direction. In addition to having the advantages of previous accelerometers, the suggested accelerometer has compensated for previous shortcomings by increasing both sensitivity and pull-in voltage. Moreover, this accelerometer is able to decrease spring torsion and spring nonlinear behavior and provide a more straightforward rigidity computation. Therefore, without increasing the total occupancy level of the sensor, this accelerometer can increase the capacitive planes’ surface area to measure acceleration in z direction, resulting in an increase in sensitivity, while all the advantages of previous accelerometers are kept. In designing this accelerometer, factors such as rise time, overshoot, settling time, and peak time were considered. The proposed properties of the accelerometer were also derived from the perspective of a second-order system. Our designed accelerometer showed an operating frequency up to 20 kHz and a dynamic range up to 1000 g. The sensitivity of the accelerometer was 4fF/g in the z axis direction. Moreover, the sensitivity of the accelerometer in x and y directions was 9fF/g.