Melting Temperature of High-Temperature Fixed Points for Thermocouple Calibrations

Abstract

Thermocouples can be calibrated at pure metal ingot-based fixed points at temperatures up to the freezing point of copper (1084.62 • C). For Pt/Pd thermocouples, the deviation from the accepted reference function very often takes an approximately linear form up to the copper fixed point. The calibration of Pt/Pd thermocouples may therefore be more amenable to extrapolation than that of Pt/Pt-Rh thermocouples. Here, the melting temperatures of a Co-C and a Pd-C eutectic fixed point are determined by extrapolating the deviation functions of several Pt/Pd thermocouples, after the fashion of Edler et al. The results are compared with the melting temperatures measured using non-contact radiation thermometry. The expanded uncertainty (k = 2) of the melting temperatures determined by extrapolation of the Pt/Pd thermocouple calibrations is ±0.32 • C for the Co-C fixed point, and ±0.49 • C for the Pd-C fixed point. For both fixed points, these uncertainties are comparable to those of non-contact radiation thermometry measurements. While a number of assumptions are made in performing the extrapolation of the calibrations, the method does appear to offer a useful complement to non-contact radiation thermometry measurements.

Computer-aided design of graphene and 2D materials synthesis via magnetic inductive heating of 11 transition metals

“…Their back-gated graphene field-effect transistors have a mobility higher than 4000 cm 2 V -1 s -1 [2]. Wu et al [3] used a solenoid coil to inductively heat copper foils up to 1100 • C-1150 • C beyond the melting point of copper at 1084.62 • C [8]. The reported cooling rate of 60 • C s −1 induced recrystallized copper from the Cu liquid phase and transformation of the Cu domains to Cu(111).…”

Fused filament fabrication process window for good interlayer bonding: Application to highly filled polymers in metallic powder*

“…The temperature history was recorded at a frequency of 1 kHz by a multiplex temperature recorder connected to K‐type thermocouples, while the feedstock material was deposited. The thermocouples were calibrated with the fixed point method [ 32 ] using the phase changes of water. The time constants of the used thermocouples, defined as the time required to respond to 63.2% of an instantaneous temperature change, were measured for 0.014 s in boiling water, considering that full temperature detection is reached after nearly 0.04 s.…”

HiTeMS: A Pan-European Project to Solve High Temperature Measurement Problems in Industry

“…This is comprised of a broad spectrum of organisations from industries, research institutes and universities with a common interest in high temperature measurement. These organisations are kept regularly informed through updates on the project website 6 . The website is interactive and enquiries about high temperature measurement problems can be posted.…”

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In my previous article [1] I discussed some of the innovations that are taking place at the National Physical Laboratory (NPL) 1 in improving high temperature measurement. Starting with the current defined temperature scale ITS-90 [2, 3], I introduced the concepts of high-temperature fixed points [4], new types of thermocouple for use to 1500°C [5,6] and developments in self-validation for contact thermometry sensors [7] and showed that high temperature measurement is undergoing a quiet revolution throughout the measurement chain. Here I want to set the work at NPL in a broader context of developments in the European Union (EU), again led from NPL, through the European Metrology Research Programme 2 project "HiTeMS: High Temperature Measurement Solutions for Industry".

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