Research Of The Laser Interferometric Measurement Technology Used For The Temperature Measurement Under Dam

Fiber optic temperature sensor has been widely applied in many fields because of its advantages of security to fire, explosion, electricity, magnetic disturbance, erosion, and dangerous environments. The interferomentric fiber optic sensor has played an important role in temperature sensing field due to its fiber structure, high sensitivity, multiplex, and universal to lots of parameters. In this dissertation a new interferomentric fiber optic temperature sensor was presented. This sensor can be used in dam, where the environment is complexity. It is safe to use and can realize remote signal transmitting. Combined the laser interferometer with the fiber-optic technique it has the advantages of insulation, explosion protection and the anti-jamming ability to electromagnetism.At first, the structure of sensing head of the new sensor with a high precision was; optimized. By particular structure, this sensing head overcame the disadvantage of conventional interferomentric fiber optic sensor which is liable to environment disturbance. A mathematical model of the temperature sensing system was established based on the measurement principle and structure of sensing head.Next, a method that uses CCD to realize conversion from light to electricity was put forward in this dissertation. CCD has advantages of auto-scanning, high sensitivity, high resolution, small volume, lightweight, mechanical vibration resistance, and the accurate pix position. Using a CCD can break through the traditional sensing method of photoelectric and be suitable to the feebleness of interference fringes output from the highly birefringence fiber optic interferometer.According to the characteristic of interference image, a suitable interference fringe processing and auto-reading method was also described in this dissertation. Furthermore, software was made to automatic pick-up the character of the interference fringe in order to obtain the displacement of the fringe with the change of temperature. The software is aiming at the low temperature change rate under the dam. The whole processing is completed automatically by computer and the measurement velocity was greatly increased.At last, experiments have been done to verify the feasibility of the newinterferomentric fiber optic temperature sensor. The experimental results show that the resolution can reach 0.01°C, and the temperature measurement system has the advantages of high automation, high precision, and real time measurement. It is safe to say that this sensor is a new method to measure the temperature and has a bright future in the application of temperature measurement both in the dam and dangerous environment.