Design, process and characterisation of a high-performance vibration sensor for wireless condition monitoring

A microelectromechanical system (MEMS) accelerometer has been developed for wireless vibration measurements on AC motors for condition monitoring. It should be a part of a cost-effective solution for a miniaturized sensor node. The requirements for such the sensor are a resonance frequency of at least 10 kHz, a highly linear response up to ±30 g and low noise floor of 5 mg RMS. For the sensor design a trade-off has been made between cost-effective development and manufacturing and the necessary higher performance of the sensor for the application compared to available off-the-shelf sensors. The sensor has been designed for manufacturing with a specially developed DRIE (deep reactive ion etch) bulk micromachining process with piezo-resistive read-out. The vibration sensor element has been encapsulated with structured glass using wafer scale adhesive bonding. Because of the design dependence of the DRIE process two manufacturing runs have been performed, regarding observed etch profiles from the first run in an improved design for the second run. Both the effects of the packaging and the imperfections of the production process on the device performance were thoroughly investigated. The sensor elements show a sufficient linear response (non-linearity