STABILITY EVALUATION OF A GOLD-PLATINUM THERMOCOUPLE AS AN INTERPOLATING INSTRUMENT IN THE TEMPERATURE SCALE

Marcelo dos Santos Monteiro, Alcir de Faro Orlando

Abstract

The 1990 International Temperature Scale (ITS-90) substituted the platinum-platinum-10% rhodium thermocouple by the high temperature standard platinum resistance thermometer (HTSPRT) and the radiation thermometer, as an interpolating instrument in the 630°C to 1064°C range, due to the lower stability of the thermocouple. Although the uncertainty of reproducing the temperature scale became much lower, the cost of the required measuring equipments was raised. Aiming to offer the Brazilian Calibration Network accredited laboratories a lower cost temperature scale traceability alternative, at a smaller uncertainty than the standard type S thermocouple can provide, a 99,999% purity gold-platinum (AuPt) thermoucouple was exposed systematically to a high temperature environment (close to 1000°C) for more than 1500 hours, with its stability and homogeneity being evaluated with the aid of a silver fixed point cell. It was shown that a ± 25 mK (k=2) uncertainty can be achieved. This works details the methodology and the cares that have to be taken in order assure the reliability of the results.

Keywords

Thermometry, Gold-Platinum Thermocouple, Interpolating Instruments

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PWC-2003-TC12-007.pdf

DOI

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IMEKO TC

TC12 - Temperature and Thermal Measurements

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