Extech Instruments 42582 User Manual page 12

Emissivity Considerations
The amount of IR energy emitted by an object is proportional to an object's temperature
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and its ability to emit energy. This ability is known as emissivity and is based upon the
material of the object and its surface finish. Emissivity values range from 0.1 for a very
reflective object to 1.00 for a flat black finish. The 42580 senses IR energy and calculates
the temperature based upon the amount of IR energy it receives using a factory default
emissivity setting of 0.95 (this setting covers 90% of applications).
Most organic materials and painted or oxidized surfaces have an emissivity factor of 0.95.
Inaccurate readings will result from measuring shiny or polished metal surfaces which have
emissivity factors other than 0.95. To compensate for polished/shiny surfaces, cover the
surface with masking tape or flat black paint. Allow time, before measuring, for the tape to
reach the same temperature as the material underneath it.
Emissivity Factors for Common Materials
Material under test
Asphalt
Concrete
Cement
Sand
Soil
Water
Ice
Snow
Glass
Ceramic
Marble
Plaster
Mortar
Brick
Emissivity Material under test
0.90 to 0.98 Cloth (black)
0.94 Skin (human)
0.96 Leather
0.90 Charcoal (powder)
0.92 to 0.96 Lacquer
0.92 to 0.96 Lacquer (matt)
0.96 to 0.98 Rubber (black)
0.83 Plastic
0.90 to 0.95 Timber
0.90 to 0.94 Paper
0.94 Chromium Oxides
0.80 to 0.90 Copper Oxides
0.89 to 0.91 Iron Oxides
0.93 to 0.96 Textiles
12
Emissivity
0.98
0.98
0.75 to 0.80
0.96
0.80 to 0.95
0.97
0.94
0.85 to 0.95
0.90
0.70 to 0.94
0.81
0.78
0.78 to 0.82
0.90
Model 42582 Version 6.0 Sept 2007