Abstract
The paper describes the metrological characterization of the highly stable Pt-40%Rh/Pt-6%Rh thermocouples to determine their reference function in the temperature range between 0 °C and 1769 °C. The preparation of the Pt-40%Rh/Pt-6%Rh thermocouples is described, as well as the measurement procedures and the measurement results of comparison and fixed point measurements for the determination of the reference function with low uncertainties.
Highlights
The current state of the art for contact thermometry measurements between about 1000 °C and 1600 °C includes the known platinum/rhodium alloyed thermocouples, Type R (Pt-13%Rh vs. Pt), Type S (Pt-10%Rh vs. Pt), and Type B (Pt-30%Rh vs.Turkey 6 Danish Technological Institute, Kongsvang Allé 29, 8000 Aarhus C, Denmark 7 Czech Metrology Institute, Brno, Czech Republic1 3 Vol.:(0123456789) 150 Page 2 of 13International Journal of Thermophysics (2021) 42:150Pt-6%Rh)
Recent investigation showed that the high temperature thermoelectric stability of Pt–Rh alloy wires improves with the mass fraction of Rh [4]
In order to facilitate the widespread use of this new Pt-40%Rh vs. Pt-6%Rh thermocouple type, its emf-temperature reference function has been established by different National Metrology Institutes (NMIs)
Summary
Their advantage is that they can be used at very high temperatures up to about 1750 °C (Types R and S) and up to about 1820 °C (Type B), but at temperatures above about 1200 °C additional drifts occurs mainly due to the increase in thermoelectric inhomogeneity. This degradation requires their regular calibration, especially when highly accurate measurements are required. Recent investigation showed that the high temperature thermoelectric stability of Pt–Rh alloy wires improves with the mass fraction of Rh [4]. In order to facilitate the widespread use of this new Pt-40%Rh vs. Pt-6%Rh thermocouple type, its emf-temperature reference function has been established by different National Metrology Institutes (NMIs)
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