Research On Ultrasonic Gas Meter Based On Time Difference Method

Gas ultrasonic flowmeter has the advantages of no moving parts,strong applicability,non-contact,large range ratio,high degree of intelligence,and has been widely used in the field of high pressure and large diameter pipeline flow measurement.However,in the medium and low pressure flow measurement,the accuracy and stability of the ultrasonic flowmeter are greatly affected by the large fluctuation of flow volume,the serious attenuation of ultrasonic signal and the serious interference of noise signals.In order to solve the above problems,a design scheme of ultrasonic gas meter based on time difference method is proposed,and a prototype of ultrasonic gas meter based on MSP430 single chip microcomputer is designed.In the flow field simulation research,two kinds of ultrasonic gas meter pipelines are designed.Based on the fluid dynamics simulation technology,the flow field distribution of the two pipelines under different flow points is analyzed,and the reasonable prototype model is determined.The system design includes hardware and software design.The hardware design includes minimum system circuit,time measurement circuit,excitation signal circuit,echo signal processing circuit,data storage circuit,intrinsic safety power circuit and human-computer interaction circuit.The software design includes main program,flight time measurement program,echo correction program,flow calculation program,digital self gain algorithm program and human-computer interaction program.In the signal processing method,the dynamic double threshold echo signal processing method is used to ensure the accuracy of the forward and reverse flow flight time measurement.For the filtering method of time difference data,an improved Kalman filtering algorithm is designed,and the correctness of the algorithm is verified by simulation.Finally,the design of the ultrasonic gas meter prototype is tested,including the introduction of the ultrasonic gas meter calibration device,transducer selection experiment,model comparison experiment and the ultrasonic gas meter cumulative flow experiment.The experimental results show that the designed prototype satisfies the requirement of 1.5 level accuracy,and has high measurement accuracy and repeatability.