TRACEABILITY TO INTERNATIONAL SYSTEM OF UNITS (SI) OF LIQUID AND GAS FLOW MEASUREMENTS – EMPHASIS TO SPECIFIC AND UNSOLVED PROBLEMSDŽEMIĆ, ZIJAD (Avtor) Drnovšek, Janko (Mentor) Širok, Branko (Komentor) measurement unitmeasurementcalibrationverificationresult of a measurementtraceabilityuncertainty of measurementmetrologymeasurement methodmeasurement proceduremeasurement resultmeasurement accuracymeasurement truenessmeasurement precisionmeasurement errorThis doctoral dissertation addresses traceability to the International System of Units (SI) for flow measurements, with the emphasis on specific and unsolved problems. It is divided into parts, according to the affinity of the problem to provide complete and traceable measurement results and calibration certificates of gas flow meters, which reflect specific installation conditions. The features of the measurement traceability are that it has a well-known history of calibrations, up to the definition of the Measurement Units, that the measurement uncertainty in the next chain becomes larger, and that the measurement uncertainty cannot be decreased by calibration with reference to the higher level standard. The main idea is to obtain complete and accurate measurement results of flow meters operating in real conditions. Therefore, the results from the calibration laboratory must additionally contain corrections and uncertainty contributions due to the specific installation situation, if necessary. When uncertainty sources are well understood and controlled, they might even be considered as corrections, therefore decreasing the overall uncertainty of the flow measuring device. The extensive research was done to allow more reliable decisions on how to deal in particular situations with the measurement uncertainty as the subject of a flow meter’s calibration, as the quantitative parameter obtained in the calibration in the laboratory, and with the qualitative statement about the accuracy of the meter operating in the field. Critical consideration about the possibilities and capabilities of calibration installations and capabilities of meters, on the one hand, and metrological requirements, on the other, are explored. New contributions, conclusions and recommendations are provided. Regarding this, the identification and characterization of the traceability issues in real-life gas measurements, conducted in complex distribution systems in terms of “installation-specific” error sources, is one of the objectives of this research. It is necessary to continually explore the sources of measurement uncertainty, which will give a better insight into the number of factors affecting the measurement process, which leads to an increased and more realistic measurement-uncertainty value. The concept of the uncertainty of a measurement result, based on a theoretical definition, in some cases, is insufficient. Because of this, measurements in real conditions will not be able to achieve the measurement uncertainty defined by written standards and will be much higher in reality. It is imperative that the estimation for all contributions that influence the measurement results are made correctly. These contributions are sometimes neglected or misinterpreted, which leads to a wrong interpretation of the measurement results, especially in real measurement conditions, resulting eventually in the wrong decisions. The unnecessary overstatement of the measurement uncertainty can increase the costs of the overall system of measurement and the control of delivery and supply, as the level of reports about the faults increases. The unnecessary understatement of the measurement uncertainty might cause too much trust to be placed in the values reported, having sometimes devastating consequences. Therefore, the overestimation of the measurement uncertainty due to the lack of knowledge is equally problematic as an underestimation. If these concerns and certain flow measurements are analyzed, the number of unsolved traceability problems of flow measurements under real conditions will decrease. A number of international normative documents and standards define measuring procedures, routes for establishing measurement traceability, the analysis and evaluation of measurement uncertainty, and the on-site calibration of gas-flow meters. However, additional considerable research is still necessary in order to improve the relevance of these documents in real-life applications from the perspective of scientific, industrial and legal metrology aspects. In order to keep as many uncertainty sources under control, the experiments conducted as part of this dissertation were made in a high-performance laboratory that has a very high quality and complexity and thus quite expensive installations. It is important to keep in mind that other sources of uncertainty coming from poor installation and by using different meter types have to be considered for each individual case. The subject of the dissertation and research is how to make the correct judgment regarding the measurement results performed by gas-flow meters using different calibration methods, legal aspects, technologies, instruments, fluids, and flow conditions, with regards to dynamic range and response. Specific unsolved flow measurement problems regarding the traceability to SI, according to the identified origin, are organized here in three chapters.20192019-05-28 10:20:11Doktorsko delo/naloga107825sl