Design Of Ultrasonic Flowmeter Based On The Travel-time-difference Method

Nowadays, with the rapid development of IC technology, there has been a great deal of interest in applying the ultrasonic to the practical field of flow measurement. The Ultrasonic flowmeter based on the travel-time-difference method is the most widely used in the liquid-measuring area. Due to the accuracy, stability, no pressure loses, wide flow-rate range, non-contact measuring, easy to fix, and low cost, the Ultrasonic flowmeter show its excellent advantages.While using the travel-time-difference method to measuring the liquid, we have to do some researches and solve many problems, mostly including: (a) The capability of the ultrasonic transducer is the foundation of the whole design. In order to generate good ultrasonic signal so as to catch the accurate liquid information, we need to research the ultrasonic transducer and its peripheral circuits, (b) The velocity of the ultrasonic wave transmitting in the liquid can reach 1500m/s, so some researches on the methods of time-calculating is very necessary, (c) A effective signal collecting and disposing system is important, (d) Research on the software system, (e) Research on the methods and equipment for the experiment.The thesis is divided into six chapters, each chapter is generalized briefly as following:The first chapter generally introduces the history and the actuality of the flowmeters, particularly introduces the present status of the ultrasonic flowmeter. The ultrasonic flowmeter based on the travel-time-difference method is selected as the subject of the thesis.The second chapter introduces the principle of the travel-time-difference method in detail and presents the main factors which influence the process of measuring so that we can confirm the problems and the difficulties.The third chapter introduces some knowledges of the ultrasonic transducer. In addition, we do some researches on the principle, the structure and the capability of the ultrasonic transducer. We also do some briefly designs of it.The fourth chapter is the most important part of the thesis. In the part of the design of hardware system, the thesis introduces the principle of the zero-cross detection for collecting the useful information from the received signal and introduces the time-calculating chip. In the software part, some functions carried out by the software are introduced.