Appendix Cemissivity; How To Determine Emissivity - RayTek Thermalert GP Series Operator's Manual

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APPENDIX C EMISSIVITY
The emissivity of a measured object is determined by the material it consists
of. Emissivity is a measure of an object's ability to absorb, transmit, and emit
infrared energy. It can have a value from 0 (shiny mirror) to 1.0 (blackbody).
C.1

HOW TO DETERMINE EMISSIVITY

Section C.2 lists common emissivity values for metals, and Section C.3 lists
common emissivity values for non-metals. If your object is not similar to any
the materials given, or extra precision is desired, you can use one of the fol-
lowing methods for determining a specific emissivity value.
1. If an accurate target temperature can be established using a contact tem-
perature probe, you may adjust the emissivity/gain setting until the IR
temperature reading agrees with the contact device reading.
2. Cover a portion of the target's surface with masking tape or flat black
paint. The emissivity of both is 0.95. Allow time for the masking tape´s
temperature to equalize with the temperature of the surface underneath.
Measure the masked area, using an emissivity/gain setting of 0.95, and
then immediately measure the unmasked area. If the two temperatures are
much different, emmissivity may affect your readings. Compensate by
adjusting emissivity while reading the unmasked area until it agrees with
the 0.95 reading of the masked area. This value should then be used
whenever that object or material is to be measured in the future.
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