A water flowmeter using dual fiber Bragg grating sensors and cross-correlation technique

Abstract In this paper, a principle and experimental results of a cross-correlation flowmeter using fiber Bragg grating (FBG) sensors are presented. The flowmeter has no electronics and no mechanical parts in its sensing part and the structure is thus simple and immune to electromagnetic interference (EMI). For water flow measurement, the flowmeter uses the time delay of the vortex signal generated by a bluff body. Karman vortex shedding frequency is also detected and utilized for the flow velocity estimation in the system. In order to realize a low noise and wide bandwidth system, we employed interferometric detection as a FBG wavelength-shift detection method. The noise spectral density of the FBG sensor with the interferometric detection was 4×10 −4  pm/(Hz) 1/2 corresponding to 0.33 ne/(Hz) 1/2 . A water flow experiment showed that the flowmeter had a linear characteristic at velocity range from 0 to 1.0 m/s and the minimum detectable velocity of 0.05 m/s.