Measurement unit for tunable low frequency vibration detection with MEMS force coupled oscillators

This paper reports on the measurement unit of a micromechanical sensor–actuator system for adjustable frequency selective vibration detection in the frequency range below 1 kHz. The sensitivity of the micro-electro-mechanical system (MEMS) is tunable and can reach values up to 400 mV/m s−2. Its spectral resolution without any electronic filtering is 105 Hz. The MEMS itself consists of two force coupled oscillators, which are operated at standard pressure. The superheterodyne principle, well known from information technologies, is then applied to the mechanical domain by the two oscillators. The intelligent silicon system is therefore used to detect the low frequency vibration, transform the vibration signal into a higher frequency range and perform amplification and filtering at a specific, tunable frequency. The analog circuitry is used to pick-off the sensor output signal and demodulate it to the baseband.