Analysis of the sensitivity and the temperature influence of a static force sensor based on a PVDF resonator

Abstract We present a new method for measuring static force or pressure using a piezoelectric element. Our structure is based on a composite resonator using poly (vinylidene fluoride) (PVDF), brass electrodes and rubber. This resonator presents a resonance-frequency shift under applied stress. The observed phenomenon is mainly due to the variation of the acoustic impedance discontinuity between PVDF and the brass electrode. We have developed a one-dimensional model to describe the resonator, then the design of the device is realized with controlled roughness of the brass electrode surface. Good results are obtained with a composite resonator having the following elements: PVDF with a thickness of 110 μm; brass electrode with a thickness of 100 μm and roughness of 1 μm; rubber with a thickness of 4 mm. This resonator leads to a sensitivity of 0.92 kHz N −1 and a measurement range of 350 N. We then present the influence of temperature on the relationship between force and frequency shift.