Liquid-level Sensor Using Embedded Fiber Bragg Grating in CFRP Diaphragm

Abstract

This article presents the development of a liquid-level sensor using fiber optic Bragg gratings (FBG). The sensor comprises a carbon-fiber-reinforced polymers (CFRP) diaphragm packaging an embedded FBG to measure strain. A mathematical analysis determines the FBG response to the pressure exerted by a liquid column over the packaged sensor. The experimental arrangement consists of an acrylic tube with a sensor at the bottom. FBG signals were acquired using a DI 410 optical interrogator manufactured by HBM. A finite element simulation with Ansys was performed to determine the most reposeful position from the FBG sensor. The experimental results show the analysis of eight repetitions of the water column ranging from 10 cm to 60 cm using 10 cm steps. The sensor showed a linear response, with a coefficient of determination of 0.999, and a sensitivity of 4.1 pm/cm; and the maximum standard deviation is 0.64 pm. Although water is used in the calibration process, other liquids could also be used, obtaining a different angular coefficient depending on the density of the liquid used.