Manufacture and precision interpolation of a film-type carbon resistance thermometer

A carbon resistance thermometer with very convenient characteristics has been developed. It allows accurate measurement of temperatures and temperature differences over a wide temperature range using a Wheatstone bridge. By varying the ratios of the constituents in the carbon mixture, the resistance and sensitivity can be varied more or less predictably. A sixth degree polynomial, fitted to calibration points in liquid helium, hydrogen and nitrogen only, gives an accurate ( R, T ) relation over the whole temperature region. This is demonstrated with a calibration against a gas thermometer. In a separate experiment the superconducting transition temperature of lead has been determined. By interpolating with the polynomial without reference to the gas thermometer, a value of 7·190°K has been obtained, in very good agreement with literature.