| Nowadays, ultrasonic flowmeter is being used widely in measuring-field. Because it has these advantages: non-connecting measurement, high precision, easy to be installed and advantageous maintenance. However, ultrasonic flowmeter could not measure the flux of little diameter pipe accurately. As for this disadvantage, basing on the basic theory and the method of the technology of measuring the flux and studying the domestic and overseas advanced technology, this paper designs a sort of high precision time-difference measuring method, which could measure the flux of little diameter pipe and presents the design of main-control circuit and the way to realize system software. The content of this paper is:1. The history of the development of ultrasonic flowmeter and methods to class the ultrasonic flowmeter are introduced.2. This paper presents the conception of flux amply. Analyzing states of liquid in the pipe and discusses the measurement technology of wide-beam and narrow-beam, and presenting the formula of computing flux and the map of theory of measurement. Then it studies the theory of the design of sing-around ultrasonic flowmeter.3. All parts of the circuit designs including SCM, keyboard, LCD and clock are described.4. The method of designing the software of LCD, keyboard, data processing, computing, self-control of gain, clock and menu of flowmeter are presented.5. The paper introduces the testing system of flowmeter, analysis of error and result of the experiment. Finally, it puts forward the way of betterment about the precision of the measurement.
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