Fe–C eutectic fixed-point cells for contact thermometry: an investigation and comparison

Abstract

Five iron–carbon (Fe–C) eutectic fixed-point cells have been constructed between NPL and LNE-Cnam to investigate the robustness and to measure the agreement of their melting temperatures. Each cell was constructed with a different selection of materials sourced by NPL and LNE-Cnam. The measured emfs at the Fe–C fixed-point temperature (∼1153 °C), compared between cells, agree within around 1.98 µV (∼90 mK), where the most important contribution to the uncertainty of each measurement is the inhomogeneity associated with the measuring Pt/Pd thermocouple. This demonstrates that these cells are suitable for use as secondary fixed-point cells in contact thermometry but the robustness of the presented cells is not found to be sufficient for maintaining their integrity during repeated cycling procedures.