Several laboratories in Europe have produced and investigated sealed triple-point cells for the realization of ITS-90 low-temperature fixed points since more than 10 years, and an international intercomparison was performed between 1978 and 1984. To investigate suspected differences between the triple-point temperatures as well as their long-term stability, a new intercomparison of cells from different sources is necessary.
It is intended to collect together cells for capsule-type standard platinum resistance thermometers from participating laboratories and to compare them in the fixed-point apparatus of the PTB. The direct intercomparison excludes possible inconsistencies due to the influence of the experimental conditions on the measured melting plateaus.
Each participant is invited to supply cells for the realization of the triple points of hydrogen, neon, oxygen, argon, and mercury, at most two cells for the same fixed-point substance. The cells should be given to the PTB together with information on the filling technology, gas purity and history as well as, if possible, together with resistance thermometers, which carry results obtained with the cells.
Progress report submitted in March 2004.