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Comparative Study of Pt/Pd and Pt-Rh/Pt Thermocouples

Ongrai, O, Pearce, JV, Machin, G and Sweeney, SJ (2010) Comparative Study of Pt/Pd and Pt-Rh/Pt Thermocouples International Journal of Thermophysics, 31 (8-9). pp. 1506-1516.

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The Pt/Pd thermocouple has demonstrated superior thermoelectric drift and homogeneity performance over conventional Pt–Rh/Pt thermocouples. Here, we present a systematic comparison of the drift and homogeneity performance of Pt/Pd and Type R thermocouples by ageing the thermocouples at 1350 °C for a total of 500 h and measuring the performance at regular intervals during this time. The thermocouples studied were one Pt/Pd thermocouple, one Type R thermocouple and one ‘special’ Type R thermocouple which was given the same preparatory annealing treatment as the Pt/Pd thermocouple prior to use. The thermoelectric stability of each thermocouple was measured at the freezing point of Ag (961.78 °C) and the melting point of Co–C eutectic (1324.29 °C). The thermoelectric homogeneity of the thermocouples was also measured. Two difference methods were used by withdrawing the thermocouple from the Ag cell and by moving a localized heat source along the thermocouple. The long-term drift of the Pt/Pd thermocouple was around 50 mK (Ag) and 65 mK (Co–C) after the first 100 h ageing at 1350 °C, followed by a further 25 mK (Ag) and 35 mK (Co–C) over the subsequent 400 h ageing. This drift performance and inhomogeneity were an order of magnitude lower than for the two Type R thermocouples. The Type R thermocouple which was given the ‘special’ preparatory treatment was about 50 % more stable than the conventional Type R thermocouple.

Item Type: Article
Authors :
Ongrai, O
Pearce, JV
Machin, G
Sweeney, SJ
Date : 2010
DOI : 10.1007/s10765-010-0782-0
Depositing User : Symplectic Elements
Date Deposited : 28 Mar 2017 15:50
Last Modified : 31 Oct 2017 14:34

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