Investigations at INRIM on a Pd–C cell manufactured by NPL

Abstract

One of a set of metal–carbon eutectic cells (a Pd–C cell, 1765 K) manufactured by NPL and used for a previous comparison of temperature scales with NIST has been investigated at INRIM. There it was implemented in two different furnaces, namely a single- and a three-zone, and measured with a standard radiation thermometer operating at 900 nm and 950 nm. Both ITS-90 and thermodynamic melting temperatures of the cell were determined by means of an extrapolation approach. The thermodynamic temperature differs by only −0.31 K from the NIST value whereas the ITS-90 temperature differs by only −0.46 K from the NPL value. The agreements, within the combined expanded uncertainties, are particularly significant, because of the different approach followed at INRIM, namely the extrapolation of multi-fixed-point scales (n = 3 and n = 4), as compared with a direct radiometric method at NIST and an ITS-90 realization traceable to the gold point at NPL.

Influence of the Cavity Length on the Behavior of Hybrid Fixed-Point Cells Constructed at INRIM

“…The ceramic work tube inside the furnace was 900 mm long with an inner diameter of 70 mm and a heated length of 600 mm [7].…”