A sensitive three-axis micromachined accelerometer based on an electrostatically suspended proof mass

A three-axis micromachined accelerometer where a free proof mass is suspended electrostatically in six degrees of freedom is proposed and tested in order to evaluate this sensitive electrostatic accelerometer for potential microgravity space applications. The micromachined device is based on a novel glass/silicon/glass bonding structure, fabricated by bulk micromachining technique and operated with closed-loop forcefeedback technology. The motion of the proof mass with respect to each side is fully servo-controlled by capacitive position sensing and electrostatic force feedback. To facilitate ground test of this low-g accelerometer, the full input range in the vertical z axis is set at a relatively high value of 3.68g in order to counteract the gravity in one g condition, while the range in the lateral x axis is set as low as 2.90mg to achieve high sensitivity. Initial test of this MEMS accelerometer shows that a sensitivity of 688.8V/g is achieved by setting a low bias voltage of 1V.