Resonant Sensors

Abstract

This chapter differs from the previous chapters in the sense that we will now discuss a class of sensors based on the operating principle of the sensor, i.e. resonant, and not on the measurand. In the previous chapters, resonant sensors have already been mentioned several times. This is not surprising as virtually every measurand can somehow be measured with a resonant sensor. In this chapter, we will present an overview of the operation and performance of resonating microsensors. A more complete discussion on the theory and applications of resonant sensors can be found in (Prak 1993) and (Wagner 1995). Other valuable papers discussing the operation of resonant sensors are (Tilmans 1992, Stemme 1991, Guckel 1990, Howe 1987). Resonant sensors are frequency output sensors and as such have several advantages:

• The (digital) output signal can be directly connected to digital signal processing electronics. Analog to digital conversion is not necessary. Furthermore, a frequency signal can be transported over long distances with no loss of accuracy.

• Large dynamic range. Time is by far the best measurand. Furthermore, the upper bound of the dynamic range is limited by the measurement time: increasing the measurement time automatically results in a larger dynamic range.