Development Of G2.5 Type Gas Ultrasonic Flowmeter

Ultrasonic flowmeter is a fast flowmeter developed in recent years.It is favored by businesses and researchers because of its small pressure loss,high accuracy,non-contact,wide range and almost no influence on gas temperature and pressure.However,the technical difficulty of the gas ultrasonic flowmeter is great,and there are many factors affecting the measurement accuracy.Influenced by factors such as transducer characteristics and flow channel structure,the measurement of 0.025-4m~3/h flow at both ends indicates that the ultrasonic receiving signal is abnormal,which makes it difficult to achieve the required accuracy and stability requirements.In this paper,read a lot of literature and field research,based on the theoretical analysis and demonstration method,mainly to solve the measurement precision of large flow and small flow point is not high,the design of G2.5 gas ultrasonic flowmeter,and the large number of calibration test,to verify the performance of flowmeter.Influenced by the transducer performance and the noise of electronic devices,the ultrasonic reception signal will superimpose small amplitude and irregular noise,which will affect the accuracy of flowmeter measurement,especially the measurement accuracy of small flow point.This paper adopts analog signal processing chip to improve the signal-to-noise ratio of the set of filters,amplifiers and comparators in one,and put forward the multi STOP signal measurement method,using the way of combining hardware with software to improve the measurement accuracy of ultrasonic gas flow meter small flow point.In the process of large volume point measurement,the amplitude fluctuation of ultrasonic signal causes the selection of signal characteristic wave inaccuracy and affects the accuracy of measurement.In order to solve the influence of ultrasonic signal amplitude fluctuation measurement accuracy,the adaptive adjustment of the hardware design of the“variable threshold+variable gain+peak detection”to achieve ultrasonic signal amplitude,and on the basis of the research on ultrasonic amplitude fluctuation of the propagation time,the ultrasonic propagation time correction algorithm.A Kalman filtering algorithm which can give consideration to smoothing effect and response rate improvement is adopted.Based on the analysis of a large number of original error data at multiple traffic points,the flow meter is corrected.Combining the two,the measuring precision of the flowmeter is further improved.The system of hardware and software in order to verify the rationality and validity of the algorithm,the calibration experiment was carried out in Jiangxi Institute of measurement and testing,and the measurement range,measurement relative error,repeatability and stability of calibration experiments,experimental results show that the measuring range of the flowmeter is 0.025-5m~3/h,meet the design goals of the system 0.025-4 m~3/h;system for measuring the maximum relative error is 0.72%;the flow is greater than the boundary point0.4m~3/h repeatability is less than 0.5%,less than meets the 0.4m3/h flow point repeatability is less than 0.9%,satisfying the national standard for the 1.5 grade precision instrument the relative error and repeatability requirements.