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Study On The Reflective Optical Fiber Bundle Hydrogen Sensor

Posted on:2011-04-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:L J CuiFull Text:PDF
GTID:1118360305492234Subject:Mechanical and electrical engineering
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Under room temperature and standard pressure, the air becomes to be exploded when the leaked hydrogen concentration is 4%-74.5% in air; therefore, the safe, reliable and cheap hydrogen sensing and detective technology is necessary for usage of the hydrogen. So far, many hydrogen sensors that based on different operational principle, are disscuced, the sensors could provide quick and active responses in normal temperature and pressure, electro-chemical hydrogen sensor are ordinary during the mentioned hydrogen sensors, potential electromagnetic interference and electric spark could arouse the catastrophic consequence. Optical fiber hydrogen sensor could satisfy the demand of safety, online detection, undisturbed surrounding, and no spark. At one time, the optical fiber hydrogen sensors possess the some features, for example, small volume, low weight, better pliability, suitable for multipoint detection in narrow space. On the side, the optical fiber could resist the interferences of chemical corrosion, the temperature and electromagnetic in tempest. Reflective optical fiber bundle hydrogen sensors was studied systematically in this dissertation, which includes correlative sensing theoretical modeling, developing and testing of hydrogen prototypes.Firstly, theoretical characteristics of the single optical-fiber couple were studied, the influence rules of related parameters in optical fiber couple were analysed, the model of reflective optical fiber bundle hydrogen sensor was established, and the results provide the theoretical principle for the optic-fiber bundle in hydrogen sensor. At the same time, for the sake of avoiding hydrogen embrittlement in previous hydrogen sensors, which were based on pure palladium, gas-sensing scheme which the sliver was added to the palladium was studied, and optimal proportioning in palladium-sliver was simulated, the reflective hydrogen sensor optical model was built up. The relationships between the palladium-sliver thickness and hydrogen concentration are studied; the optimum Pd-Ag thickness was validated through simulations and experiments.In order to improve sensor's precision and stability, and the analyzing the virtues and shortcomings of typical optical fiber path, a new design of optical fiber bundle sensing probe which was independent of any microprocessing in optical fiber was bring forward, and optical path was discussed in detail, the experiments validated the justification of sensing probe.For fabricated for Pd-Ag alloy, sputtering theoretical model was put forward, and the sputtering parameters were analysed for the ideal palladium-sliver optimal proportioning and thickness of membrane. Subsequently, the relevant details in sputtering model were discussed in detail; finally, we got the optimal supptering parameters for the palladium-sliver membrane.According to the principles of weak signal detection and signal characterics of reflective optical fieber bundle hydrogen sensor, the system of weak signal detection is designed. At the same time, phase-shift circuit, phase-sensitive circuit and dividing circuit were designed.The method, which based on virtual instrument and neural network, is studied to enhance the measuring precision and anti-interference. Compared to he hydrogen sensor, experiments using the proposed method show that the higher linear precision, the method could eliminate the inside and outside interferences as possible in sensor and realize the non-linear adjustment online.Finally, the prototypes of reflective optical fiber bundle hydrogen sensor were tested; experimental results show that reflective optical fiber bundle hydrogen sensor based on palladium-sliver alloy has good detection effects.
Keywords/Search Tags:Hydrogen sensor, Optical fiber bundle, Palladium-sliver alloy film, Reflective, Weak signal detection, Signal compensation
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