The effect of ultra-high pressure on the thermal emf of a
chromelialumel thermocouple is investigated using an indirect
method which does not require a direct knowledge of the temperature
of the pressurized junction. The unknown temperature is written
parametrically as a function of a directly measured quantity, the
electrical power delivered to the internal furnace. The emf of the
pressurized thermocouple is then written as a function of the temperature
and a set of unknown coefficients. Combining the two functions to
eliminate the unknown junction temperature, the pressurized emf is
given as a function of the furnace power. The coefficients of both the
temperature-versus-power function and the pressure-corrected emfver
sus -temperature function are then obtained simultaneously by per
forming a nonlinear least-squares fit to the directly measured emfversus
-furnace power data. Results for the temperature correction
due to pressure are compared with estimates obtained by other
methods for pressures between 25.0 kbar and 60.6 kbar and temperatures
up to approximately 900°C
