LOADED VIBRATING QUARTZ SENSORS

This paper reviews the original contributions in the development of vibrating quartz sensors, loaded with whatever medium: solid, liquid or gas. The common feature of such a loading is its ability to vibrate synchronously with the quartz resonator as a compound resonator. The paper introduces a new concept in vibrating quartz sensors, where the vibrational characteristics of such a compound resonator, namely the nominal frequency and vibrational amplitude, are correlated to the physical characteristics of the medium vibrating synchronously with the quartz resonator as a compound resonator. The energy transfer model is introduced to explain the microweighing capability of quartz resonators. Further, it is proved that microweighing is a common feature of all quartz resonators, whatever their vibrational mode. It is also proved that other piezoelectric resonators exhibit the same capability. Damping of quartz-resonator vibrations at certain temperatures during a temperature sweep is correlated with the deposited film morphology. Resonance of the gas within a cavity is used for the development of tunable gas sensors. Examples are given for hydrogen and methane detection without using a catalyst. An experiment called 'Nanobalance' is also presented, which was performed in outer space.