FBG封装材料热膨胀系数对温度传感精度的影响

The Influence of Thermal Expansion Coefficient of FBG Packaging Material on Temperature Sensing Accuracy

摘要:

光纤光栅温度传感器的增敏封装技术是促进其工程化的关键,其中增敏材料的参数特性决定了传感器的精度。讨论了奥氏体不锈钢304材料的热膨胀系数特性,研究了其热膨胀系数随温度变化的关系,分析了线性热膨胀系数对光纤布拉格光栅(FBG)温度传感公式的影响,提出用二次多项式拟合方法修正开槽钢柱封装的FBG温度系数,并搭建系统进行了实验验证。结果表明:同一温度下,实测的传感器中心波长值与采用固定热膨胀系数下的波长值相差较大,且温度越高二者差值越大,100℃时达0.075nm,温度偏差2.58℃；而实测中心波长值与采用线性热膨胀系数下的中心波长值基本一致,二者的二次多项式拟合优度达0.9999。因此,考虑封装材料的热膨胀系数变化特性,采用二次拟合方法将大大提高传感器的测量精度,适用于对温度传感精度要求较高的场合。

Abstract:

The package technology of fiber grating temperature sensor is the key to promote its engineering. In this paper, the characteristics of thermal expansion coefficient of 304 austenitic stainless steel were discussed, the relationship between thermal expansion coefficient and temperature was studied. The influence of linear thermal expansion coefficient on FBG temperature sensing formula was analyzed, a quadratic polynomial fitting method was proposed to modify the FBG temperature coefficient encapsulated in the channel steel column, and the verification system was build. Experimental results show that, under the same temperature, the measured central wavelength of the sensor is greatly different from the wavelength value obtained under the fixed thermal expansion coefficient. The higher the temperature is, the greater the difference is,and it reaches 0.075nm at 100℃ with the temperature deviation of 2.58℃. The measured value is basically consistent with the wavelength value obtained under linear thermal expansion coefficient, and the degree of quadratic polynomial fitting is 0.9999. Therefore, considering the variation characteristics of thermal expansion coefficient of packaging materials, and adopting the quadratic fitting method will greatly improve the measurement accuracy of the sensor, which is suitable for the occasions with high accuracy requirement on temperature measurement.