The Study Of Velocity Measurement Technology Based On Laser Double Beam Common Mode Compensation

In this paper,based on the laser Doppler effect,a velocity measurement method is proposed to measure the flow velocity in the complex environment of high temperature and high pressure.The direct measurement of the laser diode and the common mode compensation of the two beams are used to improve the measurement accuracy.First of all,by consulting a large number of domestic and foreign literature to understand the significance of flow velocity measurement and the research status at home and abroad,this paper analyzes the advantages and disadvantages of the typical speed measurement system.The advantages of the direct modulation technique are obtained through the analysis of the direct modulation characteristics of semiconductor lasers.Based on the understanding of the principle of laser Doppler,the analysis of the optical path of various flow velocity measurement and the theory of optical fiber,the measuring light path is designed and the mathematical model suitable for this system is derived.The heterodyne measurement can be realized by the reference beam and the measurement beam,which can improve the measurement precision and restrain the DC drift.Secondly,in order to achieve better modulation effect,the semiconductor laser diode is selected for the direct modulation of semiconductor laser.For the selection of photoelectric detector and a microprocessor to improve data processing precision;the hardware circuit of the system design,such as: the power supply circuit,laser driver circuit,modulation signal generating circuit,photoelectric conversion circuit,signal detection,demodulation,filter circuit etc..The touch screen is used to display the measurement results and the corresponding touch screen circuit is designed.The design of hardware circuit improves the measuring speed and precision.Then,in order to improve the efficiency of data processing and accuracy analysis,the spectrum analysis method,the advantages and disadvantages of counting method,fast Fu Liye transform method and so on many kinds of data processing methods,the final selection of fast Fu Liye transform higher processing efficiency to deal with the experimental data;and the program design of data processing.Intelligent way to deal with data,so that the speed and accuracy of data processing has been greatly improved.Finally,the experimental system is set up to analyze the errors in the experiment,and some measures are taken to improve it.In the performance test,to verify the feasibility of directly modulated semiconductor lasers;through the comparison with the existing laboratory measurement system experimental results validates the accuracy when the modulation frequency is 100 MHz when the system can achieve high.Error analysis and improvement of the success of the measurement error control within 1%.In this paper,the double beam common mode compensation velocity measurement system can measure the flow velocity of the fluid very well.