The Study Of Flow Measurement Based On The Optical Fiber Gating System

Flow measurement plays an important role in modern industrial production. Flowmeasurement methods based on optical fiber system have become the main direction ofthe research. Optical properties such as intensity, phase, and frequency and so on arecontrolled by the measurement when the light transmits in the optical fiber, andappropriate optical detecting methods can convert it into electrical signals. Fiber gratingsensors can measure many parameters, such as flow measurement which develops on thechange of center wavelength, and it has many advantages such as simple structure,accurate measurement, wide measuring range and many other advantages, which isgradually becoming the main mode of flow measurement. Fiber Bragg Grating(FBG)sensor is widely used in engineering monitoring of optical fiber sensing with its excellentresistance to electromagnetic interference, corrosion resistance, high sensitivity, compactand other characteristics.In this paper, we combine the principle of FBG sensor with flow measurementprinciple, and design a kind of new flow measuring device. We design a set of relativelycomplete fiber grating flow sensing system based on the principle of fiber grating sensorand flow sensor’s analysis and research, including light selection, photoelectric detector,demodulation device, signal filtering circuit, preamplifier circuit, and signal processingcircuit.On the basis of analyzing and researching the principle and demodulation techniquefor FBG, a flow measuring device of the circular target binding Fiber Bragg Grating withthe cantilever is designed. The relation between the wavelength shift of sensing FBG andthe wavelength shift of reference FBG is studied and the mathematical model based on acircular target flow measurement system is established.Stepping motor transforms the electricity pulse signal into angle-displacement orline-displacement, in the non-overload situation, the electrical machinery’s rotationalspeed and the stopping position is only decided by the pulse signal’s frequency and thepulse number, and is not influenced by the variation of load. Then it has the preparation of the running program of the stepping motor and single-chip microcomputer. This systemhas the characteristics of simply structure, high precision and low cost. The denoisingmethod of wavelet transform for signal processing, multiscale smoothing and thecombination of the linear template and multiscale smoothing denoising have obviouseffect on flow signal denoising.A scheme of demodulation technique for FBG based on the cantilever controlled bythe stepping motor is proposed, and the demodulation technique based on a pair ofmatching FBG is designed. Distributed measurement system with matching FBG filteringhas greatly improved the cost, complexity and signal-to-noise ratio of the system. Everypart of the system is designed based on the above. Matching FBG filtering detectingmethod can install sensing FBG on the measuring points according to their ownrequirements, and we only need to make the matching reference FBG with the same centerreflective wavelength to it. From the measurement array, wavelength change of matchingreference FBG can reflect the sensing FBG. Several common methods of flowmeasurement are compared by experimental tests, while, experimental data error analysiscan be concluded to verify the feasibility and precision of the design.