Analysis and Evaluation the Effect of Electrode Films on the SAW Torque Sensitivity

The surface acoustic wave (SAW) sensor has been widely used to measure torque, and the temperature effect on torque sensitivity has been taken into account. However, few studies have been devoted to the influence of electrode on the torque sensitivity. In order to design a SAW torque sensor with high performance, it is necessary to analyze the effect of electrode. We adopt the Mindlin's thin plate equations as a boundary condition due to the electrode, propose a method to evaluate the effect of electrode and make a comparison between our calculation and experimental results. Then, we obtain the frequency shifts with different electrode materials when the applied torque is zero. Finally, we evaluate the torque sensitivity with the effect of electrode and obtain the result with the errors about 1.7 and 7.6% compared with experimental data. The errors have been improved greatly with respect to the calculation ignoring electrode effect, about 30%. However, the analysis is valid only under the condition that the thickness of electrode is relatively small, which is satisfied in the general conditions.