Abstract. The Au/Pt thermocouple is the most accurate thermocouple in the temperature range of 0 to 1000 °C and is widely used in many NMIs (national measurement institutes) to disseminate the ITS-90 temperature scale in their countries. Over the years, there has been no comparison on this thermocouple within the APMP region. The objective of this comparison is to assess the degree of equivalence of the calibration results at the ITS-90 fixed-points of Ga, Sn, Zn, Al and Ag. This is a round robin comparison involving three NMIs—KRISS, NMISA and NMIA. KRISS was invited to be the pilot laboratory and was asked to prepare the two artifacts (Au/Pt thermocouple) to be circulated. This report describes the measurement procedures and equipment used in each laboratory, and compares the results and associated uncertainties obtained from the measurements by the participants. The maximum deviation at different fixed points among the three laboratories is in the range of 10 mK to 60 mK. This comparison can be used as a pilot study for another forthcoming comparison on the Au/Pt thermocouples including more participants in the APMP region.

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The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).