Fabry - Perot Cavity Level Sensor Study

Optical fiber sensor (OFS) is the important extension and development of transducer technology. With the rapid development of optical fiber information technology, people pay more attention to the OFS for its unique merits in many application fields.In order to meet the requirements for the detection of flammable and explosive continuous liquid level, based on the principle of static liquid pressure, we developed a liquid sensor by using optical fibre Fabry-Perot cavity interferometer.This sensing way needs not to modify the worksite facility; the sensor is easy to set up with intrinsic explosion-proof and high precision. This is very important to petroleum and chemical industry.After extensively surveying the literature, the thesis introduction simply reviews the present development state of liquid level sensors, and points out the limitations, especially for used to measure the inflammable and explosive liquid level.In order to help the research on this sensor, the thesis comments some transducer parameters, quality indexes and the influence of environments.Since the principle of static liquid pressure is our theoretical basis, the elastic sensing element, include the materials and structure models were discussed in detail, and this is benefit to the selection of the materials and structures of elastic sensitive elements.Chapter 4 is the major of this thesis. The features of the developed optical fibre F-P cavity structures, the parameters design and choosing, and the work point setting etc were analysed thoroughly, and combined with the practical technology, these problems were resolve in better way.The all sort of factors affecting the sensor precision were deeply and comprehensively analysed and discussed. A special structure of the elastic sensitive element with relief shape is developed; the plate design and the related parameters were introduced. This unique structure can compensate the temperature influence in a reasonable range.The temperature characteristics of the elasticity modulus of the materials were analysed deeply and we found that the flexibility of the elastic materials was severely affected by temperature changing and this should pay much attention for the materials selection.A double-sensor system was developed to enlarge the measurement range without losing the resolution.The optical fiber Fabry-Perot liquid level sensor were fabricated and the measurement results show that the sensor can give stable, high precision output...