An analytical method of electrodes mass load effect for surface transverse wave pressure sensor

A method combining perturbation theory and finite element method (FEM) with mass load effect considered, is proposed to analyze surface transverse wave (STW) pressure sensor. The proposed method firstly build a FEM model including the inter-digital transducers (IDT) structure, in which the admittance of IDT is calculated by the current on the electrodes at different frequencies. From the resonation point of calculated admittance the STW acoustics field can be obtained. Then with the stress and strain induced by pressure, and the STW acoustics field, the sensitivity of STW sensors is calculated by tile perturbation theory, which would take into account the mass load effect of IDT. An example of STW pressure sensors based on ST-90°X Quartz with pressure forced on one point is analyzed. The theoretical sensitivity with IDT's thickness of 0.17 gm and 0.21 μm is -54.9 kHz/bar and -21.7 kHz/bar respectively, which indicates that the mass load of IDT has great influence on the pressure sensitivity. Sensor with IDT'thickness of 0.17 μm is manufactured and tested, the experimental sensitivity is -57 kHz/bar. The theory coincides with experiment, which demonstrates the validity of the proposed method.