| Abstract: |
Standard Reference Material (SRM) 1749 is a lot of 18 specially-constructed gold versus platinum (Au/Pt) thermocouple thermometers, each calibrated on the International Temperature Scale of 1990 (ITS-90) and supplied with integral lead wires and a protective sheath. It is the most accurate thermocouple available over the range 0 C to 1000 C, with an expanded uncertainty (k=2) less than 8.3m C from 0 C to 962 C, and rising to 14 m C at 1000 C. We describe the fabrication and calibration methods used to prepare the SRM 1749 thermocouples. These thermocouples are exceptionally thermoelectrically homogeneous and stable over hundreds of hours of use, making them an excellent choice as a secondary reference thermometer. To facilitate low measurement uncertainties in applications, practical methods for emf measurements and comparison calibrations of other thermometers with the SRM 1749 thermocouple are also given. |
