Rusby, R L (2010) The discontinuity in the first derivative of the ITS-90 at the triple point of water. Int. J. Thermophysics, 31 (8-9). pp. 1567-1572.

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Abstract

This paper investigates the discontinuity in the derivative [dW/dT90]TPW of the ITS-90 at the triple-point of water, using data for over 40 calibrated SPRTs. It finds that the discontinuity is in most cases somewhere between 0 and - 6 parts in 105, but that the higher numerical values are obtained for 'less ideal' SPRTs (those with lower temperature coefficients of resistance), and also for sub-ranges not extending beyond the indium point.

These results are investigated vis-à-vis the long-standing observation that the ITS-90 reference values Wr(Ga) and Wr(Hg) are not completely consistent with data for W(Ga) and W(Hg) for real SPRTs. It discusses what may be done in a future scale to ensure continuity in the first derivative, and it concludes with a comment about the acceptance criteria for SPRTs in the scale.

Item Type:	Article
Subjects:	Engineering Measurements Engineering Measurements > Thermal
Identification number/DOI:	10.1007/s10765-010-0794-9
Last Modified:	02 Feb 2018 13:15
URI:	https://eprintspublications.npl.co.uk/id/eprint/4867