On non-invasive ultrasonic flowmeasurement

This thesis is concerned with non-invasive ultrasonic flow measurement, using the transit time principle. The errors associated with the transit-time flowmeter are investigated and a design of flowmeter is suggested. A theoretical and experimental study of the transmission of sound through pipe walls is carried out where it is shown that advantage can be taken of the excitation of Lamb modes. A design of transducer arrangement is made from the results of the work. A solution to the difficult problem of measuring very small times is provided in the form of a novel vernier timing system. The benefits and disadvantages of this timing system are discussed along with the design aspects of other electronic circuits required in the construction of the flowmeter. The flawmeter has been built and tested in the laboratory and is shown to be highly repeatable and accurate. The results of testing the flowmeter compare favourably with tests conducted on a commercial instrument. Improvements to the design and construction and suggestions for further work are given.