Surface-micromachined resonant accelerometer

This paper discusses the design and testing of a resonant accelerometer developed for integrated surface-micromachining processes. First- and second-generation designs are presented. The sensors use leverage mechanisms to transfer force from a proof mass to double-ended tuning fork (DETF) resonators used as force transducers. Each fork forms the basis of an integrated oscillator to provide the output waveforms. The DETFs on the first-generation device have a nominal frequency of 175 kHz, and the sensor has a scale factor of 2.4 Hz/g. The oscillators on this device exhibit a root Allan variance floor of 38 mHz (220 ppb). The second-generation, higher-sensitivity sensor uses DETFs with a nominal frequency of 68 kHz and has a measured scale factor of 45 Hz/g.