A Tunable Resonant Vibration Measurement Unit Based on a Micromachined Force Coupled Sensor-Actuator System

In this paper we present a novel microsystem for frequency selective vibration measurements in a lower frequency range. It is based on a force coupled sensor-actuator system which transforms vibration signals from a low into a high frequency range and filters the desired spectral line by means of resonance amplification. Commonly, vibration signals are detected by wideband accelerometers and subsequent fast Fourier transformation. In contrast to electronic signal transformation from a time to a frequency domain, the presented approach performs most signal conditioning in the mechanical domain. Thanks to the high Q-factor of MEMS, the signal is amplified in a very narrow band with high signal-to-noise ratio. The sense frequency can be tuned by variation of the carrier frequency and motion signals are detected by capacitive pick-up. The sensor is fabricated by BDRIE (bonding & deep reactive ion etching) silicon technology.