Pressure-Controlled Water Heat Pipe for Investigation of the Non-Uniqueness of the ITS-90 in the Range from 65°C to 157°C

摘要

A comparison measurement system based on a pressure-controlled water heat pipe was developed to investigate the non-uniqueness of the International Temperature Scale of 1990 (ITS-90) in the range from 65°C to 157°C. Its characteristics, such as the temperature stability and temperature uniformity, were measured, and the uncertainty of each source was estimated. The uncertainty of comparison measurements is only due to the temperature stability, which is within 0.034 mK. Preliminary measurements of the non-uniqueness were performed using six standard platinum resistance thermometers of the same model. The non-uniqueness plots show agreement within a maximum width of 0.08 mK, and they are within the uncertainty of the measurements of 0.05 mK (κ=2). These results indicate that the developed system can adequately detect the non-uniqueness of the ITS-90 in the water heat-pipe range.