| Summary: | The basic principle of the cross-correlation method of flow measurement is described with diagrams and mathematics. The subject of the thesis is put into perspective by a brief description of previous work in the subjects of fluidynamics and correlation flowmetering. Attention is brought to previous work done in the particular field of ultrasonic correlation flowmetering. By referring to previous work in fluidynamics, signal handling and correlation flowmetering, the author shows that there are more factors influencing the ultrasonic correlation flowmeter's performance than have previously been considered. He develops a discussion about these factors and points out how they might be expected to influence the flowmeter's performance. The flowmeter's sensor head and the acoustic sensors are illustrated and described. There is a brief description of the general purpose, laboratory correlator and the associated spectrum display unit which was used for many of the experiments. The mode of action of the industrial, self tracking, two-point-difference, flowmeter correlator is outlined. A detailed section on the sensor electronics describes the reasons for choosing phase demodulation, how a phase demodulator works and the design and reasons for the novel sensor electronics devised by the author. The flow rig is described and illustrated. Pour preliminary experiments are described together with results which show their outcome. The experiments are; the determination of the sensor electronics phase/voltage transfer characteristics, observation of the sensor's resonances and acoustic standing waves in the metered fluid, demonstration that a novel feature of the author's sensor electronics was necessary and worked and demonstration that the flowmeter was capable of working on perfectly clean liquids.
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