Theoretical and Experimental Study of z-axis Acceleration Detection of the Micro Thermal Convective Accelerometer

For the first time, we conduct theoretical and experimental analysis on the z-axis (out-of-plane direction) acceleration detection of the micro thermal convective accelerometer (MTCA). Instead of using the complex assembling method to make an out-of-plane detection structure, an indirect way to measure the z-axis acceleration is proposed. The mechanism is proposed with the evidence that the sum of the upstream and downstream detectors' temperature keeps the same under in-plane acceleration, while their differential output keeps constant with the out-of-plane (z-axis) acceleration. By means of monitoring the variation of temperature of in-plane detectors under out-of-plane acceleration, the z-axis acceleration could be indirectly sensed. Theoretically, the coupling error on z-axis induced by x-axis is quite small (less than 1%). Through this method, it could be easy to convert a single-axis (X) MTCA to a two-axis (X-Z) MTCA, which is also promising to improve the two-axis (X-Y) MTCA to a tri-axis (X-Y-Z) accelerometer. In addition, an MTCA is fabricated based on a CMOS compatible fabrication method and demonstrate the proposed detection mechanism with high sensitivity for both x-axis (1211 mu V/g) and z-axis (402 mu V/g).