Updating the reference value viscosity of water as an important element of the metrological support system for research in the field of rheology liquid media

The study focuses on the metrological support of rheological measurements of liquid media, particularly the updating of the reference value viscosity of water used in viscometer calibration. The need to update the reference value viscosity of water is justified by the fact that existing reference data on its value, presented in various sources, are quite fragmented, which may lead to inconsistencies in rheological research. The step-up calibration method, used to determine the constants of measuring instruments, is examined. The study substantiates the necessity of updating the documents OIML D 17:1987 “Hierarchy scheme for instruments measuring the viscosity of liquids”, GOST 21727-76 “Water. Viscosity at 20 °C”, and GSSSD 6-89 “Tables of Standard Reference Data. Water. Dynamic viscosity coefficient at temperatures of 0...800 °C and pressures ranging from those corresponding to a rarefied gas to 300 MPa”, due to their use of outdated values for the dynamic and kinematic viscosity of water. The influence of reference viscosity values on the measurement capabilities of the Russian Federation is investigated. Data from key comparisons on viscosity conducted by the International Bureau of Weights and Measures, CCM.V-K4:2018, demonstrating the equivalence of laboratories, are presented. The obtained results contribute to improving the accuracy and consistency of viscosity measurements in the Russian Federation, which is crucial for ensuring measurement uniformity in industry and scientific research.