Oxygen Point Calibration of a Platinum Thermometer by Intercomparison

Abstract

To examine the accuracy of transference of calibration from a reference platinum resistance thermometer to another, four thermometers, two of which are of capsule type and the others glass-stem type, are intercompared in a bath. The thermometers are inserted into wells of a copper block immersed in industrial liquid oxygen in a Dewar, the block being surrounded by glass wool to stabilize temperature of the liquid. It is concluded that a systematic error amounting to 4×10^-4 deg can arise due to possible temperature difference between the two resistances caused by difference in thermal contact with the block etc., whereas a precision of 2×10^-4 deg is obtained in terms of standard deviation insofar as the positions of the two thermometers are fixed.