Design and Implementation of Density Sensor for Liquids Using Fiber Bragg Grating Sensor

Abstract

In this paper, an optical fiber sensor based density sensor is proposed and demonstrated experimentally. The sensor is formed by fiber Bragg grating (FBG) sensor. The proposed sensor design is very simple and versatile for density measurements of liquids. The FBG strain sensor has one end mounted to a 3D printed rigid support, and the other end connected to a 3D manufactured clamp in this sensor design. A metal ball is suspended from this clamp by a non-stretchable cord. When it is completely immersed in liquid, the liquid buoyancy force acts on it. As a result, the strain in FBG varies depending on the force applied to the ball. This results in a wavelength shift in the FBG sensor. The proposed sensor design is tested for four distinct liquids, including water, gasoline, engine oil, and acetone, and the measured density values for each were tabulated. We estimated the density of water by varying the temperature and adding salt. Based on the measurements, the sensitivity of the sensor is 2.584 $\text{pm}/\text{Kg}/\text{m}^3$ when the temperature of liquid changes and $3.375\times 10^{-2}$ $\text{pm}/\text{Kg}/\text{m}^3$ when density varied by adding salt to the liquid is reported.

Keywords

• Density
• fiber Bragg grating (FBG)
• 3D printing
• oil
• hotplate
• density of water