Design and testing of a hybrid-mode PVDF displacement sensor for low-frequency infrastructure monitoring

Abstract

Polyvinylidene fluoride (PVDF) is a semicrystalline polymer exhibiting piezoelectric and pyroelectric properties which has been used for sensing infrared energy and the measurement of high frequency stress and strain, such as shocks. Despite the low material cost, durability, high sensitivity, and fast response, PVDF-based sensors have not been successfully used for infrastructure monitoring, where these benefits would seem appropriate. One reason is that the low frequency response of the sensor and integrated charge amplifier (the hybrid characteristic of the sensor) has not been adequately measured and modeled. In this paper we report on the development of a PVDF displacement sensor designed for infrastructure monitoring. The frequency response function is obtained in the range 1-45 (Hz) using a random vibration method in conjunction with a precision displacement stage. The experimentally determined response is compared to a SPICE model. The results show a characteristic high pass response with cutoff in qualitative agreement with the model. However the rolloff appears consistently more rapid, with possible attenuation at high frequencies. These results will be useful for further analysis and refinement.