基于聚酰亚胺的FBG湿度传感特性及细观特征研究

Characterization and substructure morphology of a polyimide-coated FBG humidity sensor

实现了一种采用聚酰亚胺(PI)薄膜材料涂敷的光纤布拉格光栅(FBG)湿度传感器,并研究了其表面涂覆结构、湿度传感特性、稳定性及迟滞特性。采用新的PI溶液的制备工艺,提出了一种增强PI溶液与光纤栅区的耦合方法,并利用扫描电镜(SEM)确定出4种典型的表面涂覆结构。实验结果表明,当FBG湿度传感器的PI涂覆厚小于75μm时,湿度特性曲线拟合度大于0.99,标准差小于0.5;温度特性曲线拟合度大于0.98,标准差小于0.5;其中,45μm厚的FBG湿度传感器湿度灵敏度为7.9pm/%RH,误差度为2.19%,迟滞性误差为2.6%,稳定时相对湿度波动范围小于0.8%RH。

This paper presents a kind of relative humidity（RH）sensor,which is based on fiber Bragg grating（FBG）coated with polyimide（PI）.Substructure morphology,humidity sensing characteristics,long-term stability and hysteresis characteristics of the humidity sensor are studied.The preparation and coating processes of PI are improved,and a new method to enhance the coupling between PI solution and optical fiber grating is proposed.Four typical surface coating structures are determined by scanning electron microscopy（SEM）.Experimental results show that the PI coating thickness is less than 75μm,the fitting degree of humidity characteristic curve is greater than 0.99,the standard deviation is less than 0.5,the fitting degree of temperature characteristic curve is more than 0.98,and the standard deviation is less than 0.5.The humidity sensitivity of the sensor is 7.9pm/%RH,and the nonlinear error is 2.19%at 45μm coated thickness.Hysteresis error is 2.6%,and the relative humidity fluctuation range is less than 0.8%RH.The developed device can realize the temperature compensation for humidity measurement sensor.The FBG humidity sensor also has good repeatability and stability.When compared to the conventional techniques,the novel fiber optic sensor provides a robust,relatively low-cost and continuous monitoring method.