Investigation of the Non-Uniqueness of the ITS-90 in the Range 660 Degrees C to 962 Degrees C

摘要

Preliminary results are reported on the non-uniqueness of the ITS-90 using high temperature SPRTs (HTSPRTs) in the range 660 degrees C to 962 degrees C. To achieve temperature stability and uniformity of the test HTSPRTs, the method employs the thermal isolation of the Inconel metal comparison block inside a sealed potassium heat pipe controlled to -0.01 K. Eleven HTSPRTs of three designs from five manufacturers were tested. In addition to measurements near the calibration temperatures 663.3 degrees C and 966.6 degrees C to test the temperature uniformity of the comparison block, measurements were made at 703.3 degrees C, 724.4 degrees C, 753.2 degrees C, 801.7 degrees C, 847.5 degrees C, and 913.7 degrees C.