A novel design of capacitive MEMS multi-range accelerometer; FEM and numerical approach

Abstract

Sensing the acceleration with high dynamic range follows space and size limitations and many errors and inconveniences caused by using multiple accelerometers on a single structure. A novel MEMS capacitive accelerometer with a dual-spring system has been proposed to address this issue. Such a design is a single device with two sensitivities in different sensing ranges. It increases the dynamic range of the sensing by incorporating the supporting springs at high accelerations. Therefore, the sensor can sense a more comprehensive dynamic range while maintaining the required resolution in different ranges. The design parameters of the sensor, such as the thickness of the structural layer, the size of the sensor, and the width of the spring beams, have been investigated. The mechanical sensitivity in the first range is 0.082 μm g−1. For the second range, it is 0.0015 to 0.0091 μm g−1 depending on the supportive springs’ width. Moreover, the natural frequency of the device is 1740 Hz. The capacitance change of the proposed sensor is 7 fF g−1 on average for the first range and 0.08 to 0. 48 fF g−1 for different configurations in the second range. Utilizing such sensors with changeable stiffness in different ranges can reduce the sensor footprint and fabrication cost and increase reliability.