Measure The Level Of The Corrugated Diaphragm Fiber Bragg Grating Pressure Sensor

The liquid level measurement as the automatic control and measurement important core part is applied massively in the industry field such as petrifaction in order to make sure the balance of the liquid level in each production process, and provide the reliable basis of economic accounting. It also has important significance in maintaining the regular production, ensuring yield and quality of production.Flammable liquid, such as gasoline etc, usually is preserved in sealed container of dozens of height. How to secure and reliable measurement the liquid level in the sealed container has been a important problem in petrifaction field. The flammable liquid in sealed container usually produces several million PA pressure for the bottom of container. At present, it usually use electricity sensor to measure the level of flammable liquid at home and abroad. This class sensor measurement standard has reached a higher degree of automation and definition. By using electric Power and electric transmission, this sensor is easily caused fire or explosion when measure flammable liquid. Even if it has been processed for avoid explosion which also has some risks. And it also has high price and very difficult to make measurement net.Fiber Bragg grating sensor is a new sensing technology. Obtain such as pressure, temperature, vibration, acceleration etc external parameters by the shift of Bragg wavelength. Because its measuring means and transferring process is optical signal, its Advantages is that it has no electromagnetic interference by the environment and intrinsic safe which could highly improve security and reliability of the measurement. So in the field of the liquid level measurement of flammable liquid, the fiber Bragg grating has wide application prospect. This topic use fiber Bragg grating as sensitive element to do a series of theories analysis and experimental research for related theories and technology of the liquid level measurement.Based on current condition, I select the low pressure as research object, and use relatively easyly pressure method as measurement method in order to grasp the characteristic of sensing mathematical model in practical measurement, and then give corresponding improvement method. Later, I could based on the principle of sensing mathematical model which improved by experimental verification to change material and size of sensitive elements to do the purposes of increasing range of measurement object. Now, I have done the following main work by theoretical analysis and experimental research:1. Established the sensing model based on the central deflections of the shell petal of diaphragm has a linear relation with compression press, based on changing wavelength of fiber Bragg grating pasting on the cantilever beam has a linear relation with pressure of cantilever beam, and then design a fiber Bragg grating pressure sensor using for measurement liquid level.2. According to materials and size I have calculated the theory sensitivity of this sensor. The theory sensitivity is 7pm/cm, the theory resolution is 0.14cm/pm.3. By experiment method, obtain the actual sensitivity, loading 4.9pm/cm, unloading 5.4pm/cm. The actual resolution is 0.20cm/pm.4. The results show that the shift of Bragg wavelength has a good linear relation with changing of liquid level. The experiment confirmed that the design of this fiber Bragg grating pressure sensor is feasible. It provides a good beginning for later sensor's practical research.