The Level Measurement Technology Based On FBG And Pt100and Experiments Research

With the rapid development of science and technology, liquid level measurement in various fields has been widely used in industrial production.Owing to the development of computer technology and the widely application of production control, people use computer as the upper machine to monitor the whole production process and real time control.What’s more, level measurement technology put forward higher request.It has been a key research direction to realize high precision, absolute reliability, tight security and low cost of liquid level measurement.The level measurement tends to both miniaturization and intelligence,which meets the urgent demend of industrial development in our country.In modern industrial production, the method using in liquid level measurement is various and there are also four sorts of measurement mechanisms.There are contact measurement method and Non-contact Measuring Method,different application situations choose different ways.Combining the advantages and disadvantages of the various of liquid level measurement methods,this paper puts forward a new technique of liquid level measurement,which measures the height of liquid level by means of measuring temperature.The main content of this paper is as follow:First,the structure of FBG and mechanisms of forming fiber-optic gratings are introduced.By the theoretic analysis based on the coupled-mode theory,the theory that FBG reflection center wave length and grating period are related to the effective refractive index is derived,which will lay a foundation for analysis of sensing characteristics of the fiber-bragg-gating.This paper particularly illustrates the strain and temperature sensing characteristics of FBG,and the sensitivity of temperature and strain sensitivity are derived.This illustrates that it is a good sensing element in theory which can apply its temperature sensing characteristics to liquid level measurement.And The feasibility of this theory is proved by means of designing relevant experiments.Using FBGA grating wavelength demodulation system for demodulation of grating emission spectra,finally the temperature field analysis of grating gate region is carried out by using the finite analysis tool.Furthermore,the sensing characteristics of FBG will be refined.Second,from the perspective of practical industrial production, PT100as the element of temperature measurement is applied to liquid level measurement using the same measuring principle but different ways to realize.One of the two treatment methods of liquid level measurement based on PT100is to use MCU,the other is to use PLC.Relevant hardware circuit of every method is designed,and the feasibility is confirmed by experiment.Last,the collected data is committed by wireless communication way.Using the wireless communication module PTR6100based on nRF24L01for data communication combines liquid level measuring circuit with wireless communication circuit to accomplish the whole designing of measurement system.Then the feasibility is confirmed by experiment.The paper summarizes the work and conclusion of subject research at last,puts forward the disadvantage and prospects the follow-up work.