The Float-type Density Of Fiber Bragg Grating Sensor

Density reflected the substance component and stabilization of the property, the density of the material play an important role in physics, chemistry, metrology and other disciplines. In order to ensure the stability of the liquid nature in production process, and provide a reliable foundation in the economic accounting, to maintain normal production, to ensure yield and quality of the product, and to ensure production safety, the sensor for liquid density measurement have been widely used in petrochemical, metallurgy, materials and other industrial areas.This topic chooses the intensity of beam as the sensitive components, fiber Bragg grating as the sensing element, use of immersion float-type measurement, design and machining sensor mechanical structure, select water and salt water as the experimental object of study. When the float-type fiber Bragg grating liquid density sensor all immersed in the tested liquid, the liquid density leading to the buoyancy effect the float, then the deflection of uniform strength cantilever beam intensity changes, and then the Bragg wavelength of fiber Bragg grating which pasted in the uniform strength cantilever beam shift. Through connecting fiber Bragg grating with optical signal processing system, the density of the liquid is calculated by detecting the Bragg wavelength. And using the fiber Bragg grating difference response to the temperature and density pasted on the upper and lower surface of the cantilever, this sensor can eliminate the effect of the temperature on the density measurement. The main contents of this paper are following:1,The bulk of the float which immersed in liquid is fixed value, changes of the float led to the deflection of uniform strength cantilever beam intensity changes, the changes of the beam and the shift of fiber Bragg grating has a linear relationship, calculated the model of sensor based on this relationship;2,The cantilever beam is made of 45# steel with the length of 40 mm, the bottom width is 10 mm, the thickness is 1.5 mm, The original wavelength of the fiber Bragg grating is 1555 nm. The theory sensitivity of sensor is 5.03 pm/(kg/m3), and theory resolution is 0.1988 (kg/m3)/pm.;3,According to the experiment, the measurement sensitivity of this sensor is 1.2pm/kg/m3,measurement resolution is 0.83 (kg/m3)/pm, repeatedly error is 65.354 kg/m3.