Practical Temperature Scales Between 11 K and 273 K

Abstract

The International Practical Temperature Scale has a lower temperature limit of 90.18 K; measurements below this temperature are commonly made in terms of the various "national" scales. All of these scales differ significantly from the thermodynamic scale and exhibit undesirable variations in the size of the degree as a consequence; the national scales, moreover, are comparison scales, which are widely considered to be less satisfactory than scales defined in terms of fixed points and interpolating instruments. Various proposals for replacing this mixture by a single scale have been or are being developed; these are all based, in the 12 K to 90 K range, on the results of a comparison of four national scales recently carried out at Moscow and Teddington.