Liquid Level Measurement Based on FBG-Embedded Diaphragms With Temperature Compensation

This paper proposes a fiber optic liquid level sensor system based on a silica fiber Bragg grating embedded into an epoxy resin diaphragm coupled to a temperature reference sensor, used to compensate the temperature cross-sensitivity for improving the liquid level measurement accuracy. The proposed system was tested in an industrial water tank with heating and recirculation. The results demonstrated a temperature cross-sensitivity reduction, enhancing the liquid level measurement thermal stability by a factor of nine, when compared with some single head sensor configurations reported in literature. Our system presents high linearity (R > 0.999), superior sensitivity (2.8 pm/mm), and much lower temperature related error (1.04 mm/degrees C), when compared with the other diaphragm-based sensors recently reported in the literature.