Methods of reducing the uncertainty of the self-heating correction of a standardplatinum resistance thermometer in temperature measurements of the highestaccuracy

Abstract

Self-heating of resistance thermometers is a well-known phenomenon, which occurs whenthe measuring current additionally heats up the sensing element. In the paper, theself-heating of standard platinum resistance thermometers (SPRTs) is studied with specialemphasis on the investigation and evaluation of factors which contribute to the uncertaintyof the self-heating correction. The basic two-current method for self-heating correction isanalysed and additional correction methods are proposed, based on the optimal selection ofcurrents and the use of more than two different currents. Using the advancedmethods we can decrease the uncertainty of the self-heating correction from 0.04 to0.01 mK. This decrease may not be significant in routine SPRT calibrations, but itcan present an improvement in measurements of the highest accuracy, such asintercomparisons.