Emissivity 103-
9.2 Determination of unknown emissivity
► First determine the actual temperature of the measuring object with a thermocouple or contact sensor.
Second, measure the temperature with the infrared thermometer and modify the emissivity until the
displayed result corresponds to the actual temperature.
► If you monitor temperatures of up to 380 °C you may place a special plastic sticker (emissivity dots –
Order No.: ACLSED) onto the measuring object, which covers it completely. Set the emissivity to 0.95
and take the temperature of the sticker. Afterwards, determine the temperature of the adjacent area on
the measuring object and adjust the emissivity according to the value of the temperature of the sticker.
► Cove a part of the surface of the measuring object with a black, flat paint with an emissivity of 0,98. Adjust
the emissivity of your infrared thermometer to 0,98 and take the temperature of the colored surface.
Afterwards, determine the temperature of a directly adjacent area and modify the emissivity until the
measured value corresponds to the temperature of the colored surface.
CAUTION: On all three methods the object temperature must be different from ambient temperature.
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