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4. Different methods for measuring thermal emissivity
The measurement techniques presented in this document can only be applied correctly to opaque materials, i.e. materials that are opaque under a very small thickness, of the order of a micrometer. It is possible to measure the radiative parameters (reflectance and transmittance) of non-opaque materials, but defining emissivity is tricky because of the difficulty of defining a reference temperature when the material is not isothermal, which is quite often the case.
4.1 Method classification
Emissivity measurement methods are classified into two main types, depending on the physical principle of measurement. Direct" methods are those in which the partial or total radiation radiated by the surface of the material is measured directly. Indirect" methods are those...
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Different methods for measuring thermal emissivity
Examples of commercial emissivity meters
Bibliography
Norms and Standards
- Glass in construction – Determination of emissivity - NF EN 12898 - 2001
- Standard Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques, ASTM International, West Conshohocken, PA - ASTM E408-13 - 2013
- Standard Test Method for Total Hemispherical Emittance of Surfaces up to 1 400 °C, ASTM International, West Conshohocken, PA - ASTM C835-06 - 2006
- Standard Test Method...
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