A Standardized Interpolation of Temperature using Rhodium-Iron Resistance Thermometers over the Interval 4.2 K to 24.5 K
Weston L. Tew, Richard Rusby, Peng Lin, Peter Steur, L. Lipinski, Barrie W. Ricketson
The worldwide history and current state of development of rhodium-iron resistance thermometers (RIRTs) is briefly reviewed. A standardized interpolation method using RIRTs with the nominal composition of 0.5 % Fe (by mole) is presented, with examples using data taken from 60 RIRTs made from a variety of wire batches and sources worldwide over the last 40 years. The parameterization exploits the favourable characteristics of the Cragoe reduced resistance Z() and a suitably reduced temperature . A reference function Zref() which approximates the average characteristics of selected wire is derived for use over the interval 0.65 K to 24.5561 K on the ITS-90. We examine the deviations of real RIRT data from this reference function and present simple 4-parameter Fourier-series solutions for the resulting deviation curves. Despite the fact that the wire samples may be of different origins or state-of-anneal, we find that the interpolations are successful for most of the samples studied over the 4.2 K to 24.5561 K interval, at the level of ~1 mK uncertainty or less. This method would allow for calibrations of most RIRTs over this interval using only six calibration points, permitting an efficiency not achievable using the common least-square curve-fitting calibration methods. The potential of this formalism for a standardized interpolation scheme using RIRTs is discussed.
, Rusby, R.
, Lin, P.
, Steur, P.
, Lipinski, L.
and Ricketson, B.
A Standardized Interpolation of Temperature using Rhodium-Iron Resistance Thermometers over the Interval 4.2 K to 24.5 K, International Journal of Thermophysics, [online], https://doi.org/10.1007/s10765-015-1877-4
(Accessed February 28, 2024)