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High-Temperature, Oxidation-Resistant ThermocouplesAluminum substituted for rhodium, which is scarce and expensive. Electromotive force increases with aluminum content in Pt/Al leg of Pt(Pt/Al) thermocouple. Wires baked longer in aluminizing bed produce larger voltages. Thermocouples containing platinum/aluminum legs used instead of thermocouples of type R in furnaces, heat engines, and chemical reactors. Expecially suited to high-velocity oxidizing environments. Constructed as thin-film sensors on turbine blades and vanes, where pre-oxidation provides insulating film needed between thermocouple legs. Because aluminum content slowly depleted by oxidation, long-term use recommended only where maximum temperature is 1,200 degrees C or less.
Document ID
Document Type
Other - NASA Tech Brief
Smialek, James L.
(NASA Lewis Research Center, Cleveland, OH.)
Gedwill, Michael A.
(NASA Lewis Research Center, Cleveland, OH.)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: NASA Tech Briefs
Volume: 18
Issue: 9
ISSN: 0145-319X
Subject Category
Physical Sciences
Report/Patent Number
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.

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