Piezoelectric circuitry tailoring for resonant mass sensors providing ultra-high impedance sensitivity

Abstract For piezoelectric mass sensors, the method of monitoring the impedance change at a fixed frequency have shown great promise for simplifying the measuring process and improving the robustness, as compared to the frequency sweeping method. However, it is difficult to improve such impedance sensitivity due to the highly coupling effect among the mechanical, piezoelectric and electric parameters. In this paper, an analytical impedance based sensitivity model is established by using the equivalent electric circuit theory for piezoelectric sensors. Hence, a novel sensitivity improving method is proposed through tailoring the piezoelectric circuitry by adding extra electric circuit components. For experimental validation, a piezoelectric cantilever sensor with a 21.0 mm long cantilever connected with 0.60 H inductance is fabricated and tested. For easy comparison, two dimensionless sensitivities with the same unit are introduced to evaluate the sensitivity improving efficiency. The impedance ratio sensitivity can reach 188.3/g, which is nearly 81.9 times greater than that of the frequency ratio sensitivity of 2.3/g, and also is about 4.3 times greater than that of 43.6/g obtained without any inductance, thus adequately verifying the effectiveness of such sensitivity enhancement method.