No.7（2012）12.Uncertainty evaluation on the Co-C Eutectic Point Using a Small - Type Cell as the Working Standard

Masashi Sasaki, Haruhiko Numajiri, Hiromasa Mizuno

  The National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) is currently disseminating high-temperature standards up to 2500 °C at five metal-carbon eutectic points. For calibrating a thermocouple at the eutectic point, a dedicated eutectic point furnace with a large sized cell is necessary to realize a stable and reproducible plateau.
  On the other hand, if the eutectic point can be realized by a method that is simple to use, it can find much wider applications in industry. Therefore we made a eutectic point cell for thermocouple calibration with a size small enough to fit inside a palladium fixed point electric furnace for a wire-bridge method. In this study, we performed an uncertainty evaluation to spread the calibration range of the thermocouple using the eutectic point, as a result of the Co-C eutectic point uncertainty evaluation with a small-type cell as working standards; the combined standard uncertainty is 27 mK. We accomplished a Co-C eutectic point with performance sufficient for practical use in a conventional palladium-point furnace.

Keywords
Cobalt-carbon eutectic point, Working standards, Uncertainty

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