Calibration of thermometer at low temperatures

Abstract

The calibrations of a platinum and a germanium resistance thermometer were carried out above 14K and between 5 and 15K, respectively. The platinum scale was calibrated against the triple, boiling, and sublimation points of n-H₂, Ne, N₂, O₂, and CO₂ and also their vapor pressure scales. The comparison with IPTS-68 suggests that the platinum scale has shown a deviation of +2-3mK in 8 years' time below 90K. The germanium scale was fixed by ⁴He gas thermometry. The heat capacity measurement of solid HI as an example shows that the calibrations were successfully carried out. Some remarks on such calibrations are also described.