ABSTRACT
Resonant sensors have been used in a wide range of sensing applications, such as load, pressure, torque and fluid flow characteristics. The key element of these sensors is the resonator, an oscillating structure, which is designed such that its resonance frequency is a function of the measurand. The most common sensing mechanism is for the resonator to be stressed as a force sensor. The applied stress effectively increases the stiffness of the resonator structure, whieh results in an increase in the resonator's natural frequency. The rcsonator provides a virtual digital frequency output, which is less susccptible to electrical noise and indepcndent of the level and degradation of transmitted signals, offcring good long-term stability. The frequency output is compatible with digital interfacing, requiring no analogue-to-digital conversion and therefore maintaining inherent high accuracy and low cost. Resonator sensors often have a high mechanical quality factor (Q-factor), which Icads to a high resolution of frequency and hence high sensitivity. A high Q-factor also implies low energy losses fi'om the resonator and thcrefore low power requirements to maintain the resonance, and better noise rejection outside the resonance frequency bandwidth, which simplifies the operating electronics. Rcsonant scnsors have bccn made in a wide range of types, sizes and materials [I]. This paper describes a metallic triple-beam tuning fork resonant force sensor with screen-printed thick film lead zirconate titanate (PZT) drive and sense elements [2] and presents initial results from the device.
