Assessment of platinum versus palladium thermocouple by comparison against photoelectric radiation pyrometer and noble metal thermocouples

摘要

Platinum versus palladium (Pt/Pd) thermocouple, fabricated with high purity wires is now-a-days becoming attraction of researchers to find its application as a high temperature precision sensor. The performance of a Pt/Pd thermocouple when measured by two different techniques of contact and non-contact ways of temperature measurement by comparison method, has been investigated. The Pt/Pd thermocouple has been compared in terms of its electromotive force in μV against a calibrated Type-S or Type-R thermocouple in a spherical blackbody temperature source, having emissivity of 0.98 and using a photoelectric linear pyrometer. The high stability tungsten strip lamps were used as reference standard radiation sources for comparing photoelectric pyrometer, which in turn has been used as a transfer standard for accurately determining the temperature of spherical blackbody source. The experimental results have shown a close agreement between two different techniques used and also an evidence on the advance characteristics of Pt/Pd thermocouple over Type-S or R thermocouple in the high temperature range from 800° to 1300°C. The uncertainty in the comparison from various sources in the measurement for evaluating temperature was estimated to be within ± 0.65°C at 800°C and ± 0.47°C at 1300°C.