条纹计数法干涉型光纤液位传感器的电路法判向及其温度补偿

Direction change judgment by double circuits and temperature compensation for optical fiber Fabry-Perot cavity liquid level sensor with fringe counting

提出利用RC移相电路获得相位差为90°的输出信号,以取代相位差为90°的双光路,对干涉条纹计数时做正确判向,可以简化条纹计数法光纤Fabry-Perot腔干涉型液位传感器的结构,使之更实用和集成化。分析了F-P腔长与温度变化的关系,说明选择合适的腔体材料以及波纹管的热膨胀系数和初始长度,可在温度变化时保持腔长的较小变化。提出在传感器上安置温度传感器,预先测出F-P腔长与温度变化的关系,然后利用软件法对传感器输出进行温度补偿。实验表明:该软件补偿法能够较好的补偿温度变化对液位测量时造成的影响。

A method for accurately judging the direction change by using π/2 electric RC phase shifter during the interference fringe counting for optical fiber Fabry-Perot cavity liquid level sensor is proposed. Instead of using double optical channels, the structure of the sensor system could be then simplified and be more compact and practical. After analyzing the relationship between the F-P cavity length and temperature, if the materials, initial lengths, and thermal expansion coefficients of the interior and exterior of the cavity were properly chosen,the cavity length change could be kept as small as possible. A novel design for compensating temperature influence on the sensing result by software approach is suggested. The experimental results show that this software technique can effectively compensate the temperature drift impact.