5D-2 Application of a Portable RF Impedance Spectrum Analyzer for the Investigation of Lateral Field Excited Acoustic Wave Sensors in a Liquid Environment

Lateral field excited (LFE) AT-cut quartz sensors, vibrating in the transverse shear mode, are capable of determining both mechanical (mass, density, viscoelasticity) and electrical property changes (conductivity, permittivity) in an adjacent liquid medium. The LFE sensors´ response to these property changes arises from the electrodes, which are deposited on only one crystal surface resulting in an electric field between the electrodes and which penetrates into the adjacent media. In order to determine the influence of the liquid property changes on the sensor response, the entire impedance spectrum of the LFE sensor must be measured. In lieu of a standard bench top network analyzer, a compact impedance analyzer that is specifically interfaced to the LFE sensor is employed.