Greenlee TG-100 Instruction Manual page 12

Emissivity
Emissivity is the ability of an object to emit heat. Most objects or surfaces have an emissivity
value of about 0.95. This is the pre-set emissivity value of the TG-100.
Some objects, such as polished or shiny metallic surfaces, may have much lower emissivity.
Using a temperature gun to measure the temperature of such objects will produce inaccurate
results.
• Temperature readings will be inaccurate on highly reflective objects.
• Temperature readings will be inaccurate on objects if emissivity is not adjusted
properly. Follow masking and emissivity adjustment procedures.
Failure to observe these precautions can result in injury or property damage.
TG-100
To determine the effect of emissivity on the measurement, cover the surface with masking
tape or flat black paint. (Be sure to use tape or paint that can withstand the anticipated
temperature.) The emissivity of both these materials is about 0.95. Allow time for the tape or
paint to reach the temperature of the material underneath. Measure the covered area and a
nearby area. The readings should be about the same. If they are not, the emissivity may affect
your measurements.
TG-200 and TG-300
• If the temperature of the surface is known, adjust the emissivity until the unit agrees with
the known temperature.
• If the material of the surface is known, adjust the emissivity according to the Common
Emissivities table on the following page.
• Otherwise, mask the surface as described above. Measure temperature of the masked area
with emissivity set at 0.95. Measure temperature of unmasked surface and adjust emissivity
until temperatures agree. Write down emissivity value for future readings on this surface.
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