Evaluation of a pressure-controlled water heat pipe for accurate comparison of platinum resistance thermometers

A pressure-controlled water heat pipe was evaluated as a comparison furnace for Standard Platinum Resistance Thermometers (SPRTs). Its calibration uncertainties in the range from 65/spl deg/C to 157/spl deg/C were estimated. In direct comparison of SPRTs with a calibrated SPRT, the combined uncertainty of the comparison is estimated to be 0.081 mK. On using the heat pipe as a calibration facility, the combined uncertainty of the calibration is estimated to be 3.1 mK.