Research And Experiment On Spiral Optical Fiber Liquid Level Sensor

Aircraft fuel level is an important indicator of the aircraft fuel measurement. Duringthe measurement of the fuel level, the existing aircraft fuel level sensor can’t fully meetthe needs of Aircraft fuel level measurement as the environment with flammable andexplosive characteristics, ambient temperature and pressure changes large, the tanksometimes inadvertently mixed with a small amount of water. The optical fiber sensor isvery suitable for the measurement of the high security requirements of Aircraft fuel levelsince small size, anti-interference ability, electrical isolation and high sensitivity.This thesis introduces the principles of side-emitting optical fiber level sensor.Combined with the theoretical model, proposed using a spiral structure increases thedifference of the attenuation coefficient of the sensor in the air and liquid, therebyincreasing the sensitivity of the sensor, according to the spiral-shaped structure designed toproduce three different pitch sensors. The signal detecting circuit of the sensor is designedbased on the principles of modulation and demodulation, which highlights the design oflight source and the light detector in use of the LED and photoelectric diode. Based on theprinciple of weak signal detection, the signal conditioning circuit is designed by Lock-inAmplifier (LIA).According to environmental conditions, we designed a platform for level experiments.During the experiment of the sensor’s temperature drift characteristics, we received thetemperature characteristics of sensor’s various parts. Temperature drift characteristics ofLED is a major factor in the whole set of devices affected by temperature. During the leveldynamic repeatability test of the three pitch sensors, the results show that spiral fiber levelsensor for the continuous measurement of the liquid level is feasible, wherein15mm pitchcharacteristics of the sensor is the most stable, with the value of the actual engineeringapplication.