RESULTS OF AN INTERNATIONAL COMPARISON OF WATER TRIPLE-POINT CELLS

The reference temperatures of a large number of triple point of water cells collected from manufacturing sources around the world have been compared at the BIPM and in twelve national laboratories. This allowed an assessment to be made of the reproducibility of the realizations o f the triple point of water and the equivalence of the experimental pr ocedures. The results show that, in most cases, the temperatures of th e cells agree to within +/-0,1 mK. In some cases, however, much larger differences and temperature changes were observed, for which no obvio us explanation has so far been found. The results also provide a compa rison of a large number of national reference cells.