42582 Datasheet, PDF (12/14 Pages) Extech Instruments Corporation. – IR Thermometer Printer / Datalogger with External Contact Probe

Emissivity Considerations
The amount of IR energy emitted by an object is proportional to an object's temperature
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 Emissivity
Asphalt
0.90 to 0.98
Concrete
0.94
Cement
0.96
Sand
0.90
Soil
0.92 to 0.96
Water
0.92 to 0.96
Ice
0.96 to 0.98
Snow
0.83
Glass
0.90 to 0.95
Ceramic
0.90 to 0.94
Marble
0.94
Plaster
0.80 to 0.90
Mortar
0.89 to 0.91
Brick
0.93 to 0.96
Material under test
Cloth (black)
Skin (human)
Leather
Charcoal (powder)
Lacquer
Lacquer (matt)
Rubber (black)
Plastic
Timber
Paper
Chromium Oxides
Copper Oxides
Iron Oxides
Textiles
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
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Model 42582 Version 6.0 Sept 2007