RayTek MI Miniature Infrared Sensor - Manual (Page 91)

Appendix
MI 83
12.2 Typical Emissivity Values
The following table provides a brief reference guide for determining
emissivity and can be used when one of the above methods is not
practical. Emissivity values shown in the table are only approximate,
since several parameters may affect the emissivity of a material.
These include the following:
1. Temperature
2. Angle of measurement
3. Geometry (plane, concave, convex)
4. Thickness
5. Surface quality (polished, rough, oxidized, sandblasted)
6. Spectral range of measurement
7. Transmission (e.g. thin films plastics)
To optimize surface temperature measurements, consider the
following guidelines:
• Determine the object emissivity using the instrument which is
also to be used for the measurements.
• Avoid reflections by shielding the object from surrounding
temperature sources.
• For higher temperature objects use instruments with the
shortest wavelength possible.
• For translucent materials such as plastic foils or glass, assure
that the background is uniform and lower in temperature than
the object.
• Mount instrument perpendicular to surface if possible. In all
cases, do not exceed angles more than 30° from incidence.