THE CALIBRATION OF PLATINUM RESISTANCE THERMOMETERS IN THE TEMPERATURE RANGE 11° TO 90°K

A set of six platinum resistance thermometers of a form suitable for low temperature calorimetry has been made and calibrated in the region 11° to 90°K. by intercomparison with a similar thermometer which had been calibrated at the National Bureau of Standards. Above 90°K. calibration has been made on the International Temperature Scale.Using the intercomparison data, it has been possible to derive a method whereby for these thermometers the scale for the region 20° to 90°K. may be found to within 0.002°C. by means of fixed points. The method applies a 'Z function' of the type used at the National Bureau of Standards (13), plus a corrective term which depends upon the resistance of the thermometer at the boiling point of hydrogen and upon the normal constants which are determined for the International Temperature Scale above 90°K.