Experiment On Optical Fiber Liquid Level Measurement System

Aircraft fuel quantity measurement system is related to the safe operation of the aircraft.The fuel level sensor is one of the most important parts of the system. Domestic aircraft fuellevel sensor technology is relatively backward. The capacitive sensors are most widely usednow. However, this kind of sensor may cause electronic spark, and has another problem of“water pollution”: when the fuel ismixed with the condensed water, the capacitive sensorwill give a wrong indicating value or even suffer short circuit. Therefore, it has greatsignificance to research new fuel level sensor technologys. There are many advantages ofoptic fiber sensors, sucha as intrinsically safe and immune to electromagnetic interference.Many kinds of optical fiber liquid level sensor have been developed now, but only thelight-leaking sensors are potentially suitable for aircraft fuel gauging.This thesis describes an aircraft fuel level measurement system based on the spiral sideemitting optical fiber sensors. The sensor is made of side emitting fiber, and a spiral structureis adopted to improve the sensitivity. The lock-in amplification circuits are utilised to extractweak signals from the strong noise.According to the actual measurement condition of fuel level, a simulation test devicehas been built to detect the fuel level, and a series of experiments are developed. Theexperiment results show that the spiral light-leaking optic fiber sensor is feasible forcontinuous fuel level measurement. Among the three sensors, the sensor with a pitch of15mm has the best performance. Some problems of the sensors are exposed through theexperiments, and the corresponding solution ideas have been put forward. Attitude errorwhich may affect the accuracy of the sensor, is analyzed and calculated, and the mostsuitable sensor installation location which may minimum the attitude error is put forward.