Final report on the intercomparison EUROMET.M.D-K1 of volume standards by hydrostatic weighing (EUROMET project 339)

This report describes the result of a key comparison of volume standards at twelve European national metrology institutes. This comparison was carried out during the period January 1996 to January 1999 within the framework of the European Collaboration in Measurement Standards (EUROMET) in order to determine the degree of equivalence between the participants for the determination of the volume of solids in the range 87 cm3 to 315 cm3. The pilot institute was the Federal Office of Metrology METAS (former OFMET) of Switzerland. This comparison was initiated and realized before the CCM.D-K1 (Density measurements of a silicon sphere). For that reason no direct link was made between the CCM.D-K1 and the EUROMET.M.D-K1 comparison. The transfer standards consisted of three different spheres made of ceramic material (Si3N4/MgO). The three spheres were calibrated by the participants using hydrostatic weighing either with solid density standard or with water density tables as reference. Stability measurements show that the transfer standards were sufficiently stable during the comparison. The degrees of equivalence of the measurement standards were expressed quantitatively by two terms, deviations from the key comparison reference values and associated uncertainty of measurement for each of the three spheres. Considering all participants, the maximum relative difference between the volume measurements was 1.6 X 10-5 for the biggest sphere (1 kg and 315 cm3). Considering the five participants using a solid density standard as volume reference and having performed automatic mass determination, the maximum relative difference between the volume measurements was 2.2 X 10-6 for the same sphere. This comparison was approved for provisional equivalence of the CMC declared in the field.