Determining Emittances for Use in Infrared Thermometry: A Simple Technique for Expanding the Utility of Existing Methods

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  • 1 U.S. Water Conservation Laboratory, Phoenix, Ariz. 85040
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Abstract

A simple laboratory technique is described for making rapid emittance measurements with an infrared thermometer. It is shown that when the infrared thermometer head is held flush against a surface, its output is a linear function of surface emittance. Thus, viewing two or more surfaces of known emittance in this manner “calibrates” the infrared thermometer, so that viewing an unknown surface at the same temperature in this manner will yield its emittance., Emittance values of the standard surfaces employed may be obtained via any of a variety of emittance measurement methods previously developed. A nomograph is presented that shows the possible errors that can occur as a result of temperature differences that may exist between the test and standard surfaces.

Abstract

A simple laboratory technique is described for making rapid emittance measurements with an infrared thermometer. It is shown that when the infrared thermometer head is held flush against a surface, its output is a linear function of surface emittance. Thus, viewing two or more surfaces of known emittance in this manner “calibrates” the infrared thermometer, so that viewing an unknown surface at the same temperature in this manner will yield its emittance., Emittance values of the standard surfaces employed may be obtained via any of a variety of emittance measurement methods previously developed. A nomograph is presented that shows the possible errors that can occur as a result of temperature differences that may exist between the test and standard surfaces.

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