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• For surfaces that are effective at radiating energy (high emissivity), the emissivity factor is ≥0.90.
• This simplification does not work on shiny surfaces or unpainted metals, as these have an emissivity of <0.6.
These materials are not good at radiating energy and are classified as low emissivity.
• To measure materials with a low emissivity more accurately, an emissivity correction is necessary.
• Adjusting the emissivity setting will usually allow the thermal imager to calculate a more accurate estimate of the
actual temperature.
• For more information, please see the Emissivity Adjustment section below to get the most accurate temperature
measurements.
k) Emissivity adjustment
• The correct emissivity value is important to make the most accurate temperature measurement.
• The emissivity of a surface can have a large effect on the apparent temperatures that the thermal imager observes.
• Understanding the emissivity of the surface may (although not always) allow you to obtain more accurate
temperature measurements.
Note: Surfaces with an emissivity of <0.60 make the reliable and consistent determination of actual temperature
problematic. The lower the emissivity, the more potential error there is associated with the imager’s temperature
measurement calculations. This is also true even when adjustments to the emissivity and reflected background
adjustments are performed properly.
• Emissivity is set directly as a value or from a list of emissivity values for some common materials.
• The global emissivity displays on the LCD Screen as E=x.xx.
The following table gives the typical emissivity of common materials.
Material
Emissivity
Water
0.96
Stainless steel
0.14
Aluminium plate
0.09
Asphalt
0.96
Concrete
0.97
Cast iron
0.81
Rubber
0.95
Wood
0.85
Brick
0.75
Tape
0.96
Brass plate
0.06
Human skin
0.98
PVC plastic
0.93
Polycarbonate
0.80
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