Au Fixed Point Development at NRC

Article

Abstract

Two Au fixed points filled using metal of different nominal purities in carbon crucibles have been developed at the National Research Council Canada (NRC). The primary motivation behind this project was to provide the means for direct thermocouple calibrations at the Au freezing point (\(1064.18~^\circ \hbox {C}\)). Using a Au fixed point filled with the metal of maximum available purity [99.9997 % pure according to glow discharge mass spectroscopy (GDMS)], multiple freezing plateaus were measured in a commercial high-temperature furnace. Four Pt/Pd thermocouples constructed and calibrated in-house were used to measure the freezing plateaus. From the calibration at Sn, Zn, Al and Ag fixed points, the linear deviation function from the NIST-IMGC reference function (IEC 62460:2008 Standard) was determined and extrapolated to the freezing temperature of Au. For all the Pt/Pd thermocouples used in this study, the measured EMF values agree with the extrapolated values within expanded uncertainty, thus substantiating the use of 99.9997 % pure Au fixed point cell for thermocouple calibrations at NRC. Using the Au fixed point filled with metal of lower purity (99.99 % pure according to GDMS), the effect of impurities on the Au freezing temperature measured with Pt/Pd thermocouple was further investigated.

Keywords

Gold Metal fixed point Pt/Pd thermocouple 

Notes

Acknowledgements

The authors would like to thank Douglas Gee for his help in measuring the immersion profiles for the Pt/Pd thermocouples, Kate Swider for the GDMS measurements and Patrick Rourke for useful discussions.

References

  1. 1.
    H. Preston-Thomas, Metrologia 27, 3 (1990)ADSCrossRefGoogle Scholar
  2. 2.
    H. Preston-Thomas, Metrologia 27, 107 (1990). [erratum]ADSCrossRefGoogle Scholar
  3. 3.
    J. Ancsin, K.D. Hill, Metrologia 30, 507 (1993/94)Google Scholar
  4. 4.
    K.D. Hill, Metrologia 52(4), 478 (2011)ADSCrossRefGoogle Scholar
  5. 5.
    A.D.W. Todd, M. Gotoh, D.J. Woods, K.D. Hill, Int. J. Thermophys. 32(1–2), 441 (2011)ADSCrossRefGoogle Scholar
  6. 6.
    A.D.W. Todd, M. Gotoh, D.J. Woods, K.D. Hill, Int. J. Thermophys. 32(1–2), 453 (2011)ADSCrossRefGoogle Scholar
  7. 7.
    G.W. Burns, D.C. Ripple, M. Battuello, Metrologia 35(5), 761 (1998)ADSCrossRefGoogle Scholar
  8. 8.
    Y.G. Y.-G. Kim, Z. Wei, H. Ogura, F. Jahan, Y. Singh, APMP regional comparison of Co–C eutectic melting point using Pt/Pd thermocouples. Tech. Rep. APMP.T-S7, Korea Research Institute of Standards and Science, Korea (2015)Google Scholar
  9. 9.
    K. Hill, D. Gee, in Temperature: Its Measurement and Control in Science and Industry, AIP Conf. Proc., vol. 8, AIP Conf. Proc., vol. 8 (2013), pp. 520–525Google Scholar
  10. 10.
    Evaluation of measurement data—Guide to the expression of uncertainty in measurement (2008)Google Scholar
  11. 11.
    B. Fellmuth, K.D. Hill, J. Pearce, A. Peruzzi, P. Steur, J. Zhang, Guide to the realization of the ITS-90: Chapter 2: Metal Fixed points: Section 2.1: Influence of Impurities, Edition 2015. (2015). http://www.bipm.org/en/committees/cc/cct/guide-its90.html
  12. 12.
    B. Fellmuth, K.D. Hill, J. Pearce, A. Peruzzi, P. Steur, J. Zhang, Guide to the realization of the ITS-90: Chapter 2: Metal Fixed points: Appendix 2: Distribution coefficients and liquidus line slopes (2015). http://www.bipm.org/en/committees/cc/cct/guide-its90.html
  13. 13.
    J. Schooley, Thermometry (CRC Press Inc, Boca Raton, 1986)Google Scholar

Copyright information

© Her Majesty the Queen in Right of Canada 2017

Authors and Affiliations

  1. 1.National Research Council of CanadaOttawaCanada

Personalised recommendations