PREPARATION FOR A COMPARISON OF PLATINUM-IRIDIUM KILOGRAM MASS STANDARD AMONG NMIS IN APMP

The kilogram is unique among the base SI units in being the only one defined by an artefact. A major problem with maintaining the traceability of the mass scale is the inherent instability of the kilogram artefacts. To resolve the problem, there had been done a comparison of the values of the national standard kilogram of 18 European National Metrology Institutes (NMIs) by National Physical Laboratory (NPL) in England. The similar comparison in APMP is needed to plan as a pilot study. The ten institutes of APMP are participated in this pilot study. KRISS in Korea and NMC/ASTAR in Singapore act as a pilot and a co-pilot laboratory respectively. The travelling standard (No. 651) used for comparison among European NMIs is provided by NPL. In this paper, the preparation of comparison and the interim result for stability of the travelling standard at KRISS will be presented.