Abstract :
The highest-temperature, defining fixed point of the IInternational
Temperature Scale of 1990 (ITS-90) is the copper freezing point (1,084.62◦C). Many
iInternational metrology institutes are investigating the use of transition temperatures of
metal–carbon alloys as references for the calibration of temperature measuring instruments
above the copper point, making it possible to reduce the calibration uncertainty
of pyrometers in radiation thermometry and thermocouples in contact thermometry.
This research is being performed mainly by radiation thermometry laboratories that
have developed specific cells with blackbody cavities containing relatively small quantities
of metal–carbon alloys. Parallel to this, some laboratories have also developed
cells with these same alloys, but of a different design, suitable for the calibration of
thermocouples. This report concerns the development of a nickel–carbon eutectic cell
(∼=
1,329◦C) at Inmetro, with which either a radiation thermometer or thermocouple
can be calibrated. The measurements of the temperature of this cell were performed
using the reference radiation thermometer of the Pyrometry Laboratory and Pt/Pd
thermocouples that were constructed, stabilized, and calibrated at the Thermometry
Laboratory. Details of the cell fabrication, as well as the instrumentation used for the
measurements are given. The results of a comparison between the two different types
of measurement are reported, including the uncertainty budgets of both methods.
