MEMS vibration sensors have a clear advantage over precision-engineered sensors due to their high degree of miniaturization and integration as well as low manufacturing costs. Currently, however, the MEMS sensors available on the market cannot yet sufficiently fulfill the requirements regarding high sensitivity and simultaneously large bandwidth (>> 5 kHz) as well as detection of all three spatial directions (3D) at the lowest possible power consumption and often only provide analog signals.
Fraunhofer ENAS is involved in the development of broadband MEMS vibration sensors for a wide range of applications Current sensor systems are suitable for the detection of vibrations with a 5 % bandwidth of 8.8 kHz. Sensor systems under development should be able to measure vibrations up to 30 kHz bandwidth (3 dB) in the future. As the bandwidth increases, the sensitivity of the sensors decreases immensely. To counteract this, technologies are needed that allow ever smaller gap dimensions to be realized. In addition, the electronics must be designed to be very sensitive and low-noise. To achieve the smoothest possible transfer function, the sensors must not exhibit any resonance overshoot. As a result, the noise caused by the MEMS can be significantly reduced only by a relatively high intrinsic weight and thus structure height. However, this is contrary to the requirement for very small gaps.