Investigation of the furnace effect in cobalt-carbon high-temperature fixed-point cells. (August 2017)

• Record Type: Journal Article
• Authors: Dong, W.; Lowe, D.; Machin, G.; Bloembergen, P.; Wang, T.; Lu, X.
• Is Part Of: Measurement. Volume 106(2017)
• Page Start: 88
• Page End: 94
• Publication Date: 2017-08
• Subjects: Eutectic -- Fixed point -- Furnace effect -- Radiation thermometry -- HTFP; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2017.04.005
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: Discrepancy in melting temperature of high-temperature fixed-point observed. Evidence for an unaccounted for effect. Additional uncertainty values proposed. Abstract: Temperatures with associated uncertainties are to be assigned to high-temperature fixed-points. It is important that those uncertainties are large enough to cover the sources of error but not so overstated as to unnecessarily reduce the usefulness of the fixed-points. Concerns have been raised about unexplained differences between the same fixed-point measured in different furnaces; here we investigate the effect of using three different furnaces on the freezing and melting behaviour of two Co-C eutectic fixed point blackbody cavities. Each furnace had significantly different temperature profiles. The results indicate that the most uniform furnace yielded a higher melting temperature by over 100 mK. Investigation of possible confounding effects: the effect of furnace uniformity on melting curve shape, the micro-structure of the ingot, the temperature drop across the cavity wall, the cavity emissivity and the size-of-source effect show that these factors together are too small to account for the overall observed difference.