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Use of a Multiwavelength Pyrometer in Several Elevated Temperature Aerospace ApplicationsA multiwavelength pyrometer was developed for applications unique to aerospace environments. It was shown to be a useful and versatile technique for measuring temperature, even when the emissivity is unknown. It has also been used to measure the surface temperatures of ceramic zircomia thermal barrier coatings and alumina. The close agreement between pyrometer and thin film thermocouple temperatures provided an independent check. Other applications of the multiwavelength pyrometer are simultaneous surface and bulk temperature measurements of a transparent material, and combustion gas temperature measurement using a special probe interfaced to the multiwavelength pyrometer via an optical fiber. The multiwavelength pyrometer determined temperature by transforming the radiation spectrum in a broad wavelength region to produce a straight line (in a certain spectral region), whose intercept in the vertical axis gives the temperature. Implicit in a two-color pyrometer is the assumption of wavelength independent emissivity. Though the two data points of a two-color pyrometer similarly processed would result immediately in a similar straight line to give the unknown temperature, the two-color pyrometer lacks the greater data redundancy of the multiwavelength pyrometer, which enables it to do so with improved accuracy. It also confirms that emissivity is indeed wavelength independent, as evidenced by a multitude of the data lying on a simple straight line. The multiwavelength pyrometer was also used to study the optical transmission properties of a nanostructured material from which a quadratic exponential functional frequency dependence of its spectral transmission was determined. Finally, by operating the multiwavelength pyrometer in a very wide field of view mode, the surface temperature distribution of a large hot surface was obtained through measurement of just a single radiation spectrum.
Document ID
20010035857
Acquisition Source
Glenn Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ng, Daniel
(NASA Glenn Research Center Cleveland, OH United States)
Fralick, Gustave
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
September 7, 2013
Publication Date
February 1, 2001
Publication Information
Publication: Review of Scientific Instruments
Volume: 2
Issue: 2
Subject Category
Instrumentation And Photography
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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