In the presented work, we wanted to check the effect of the measuring shaft with the associated fixtures on the measurement uncertainty of the three tested flow meters. The reader is presented with theoretical background of flow measurements, their purpose, application, various measurement technologies, telemetry, and measurement uncertainty and its determination. The master’s thesis was based on the implementation and analysis of the flow measurements I performed in the laboratory of the Department of Mechanics of Liquids at the Faculty of Civil Engineering and Geodesy, University of Ljubljana. The tested flow meters were turbine gauge (Flostar M), ultrasonic meter (FlowIQ 3100) and electromagnetic measuring rod (Signet 2552 Magmeter). As a reference gauge, I used Thomson weir with a standardized top plate which has a V-notch (angle 53 ° 8 '). In the first set of measurements, I wanted to determine the influence of the measuring shaft with the associated fixtures (two FF connectors, a dirt catcher, a disassembling piece and locking fixtures) on the measurement uncertainty of the tested meters. In addition, I carried out an additional set in which I met all the installation conditions of the manufacturer and checked how that influences the associated measurement uncertainty. In analyzing the results, we complied with the requirements of International Standard ISO 5168: "Measurement of Liquid Flow - Uncertainty Assessment Procedures" of 2005. For each meter we determined the measurement uncertainty of type A as a function of flow. I showed the results of the measured flows and the associated extended measurement uncertainty in the form of graphs, standard ISO 5168.
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