Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

1. Apply the reference emitter (E) to a portion of the target (an area of at least
one square inch is normally adequate).
2. Set the imager to measure isotherm units.
3. Measure the background thermal level (B) adjacent to the target. Do this
by placing a piece of cardboard to which is applied a crumpled, flattened
piece of aluminum foil. Take this measurement over a large area of the foil.
(An area of at least one square foot is normally adequate.)
4. Measure the target thermal level (T).
5. Measure the reference emitter level (R). The reference emitter must be in
thermal equilibrium with the target. This thermal equilibrium condition will
be apparent when the reference emitter thermal level is not changing. (In
the case of dye check developer, its application cools the surface as the
propellant evaporates. Wait at least 15 minutes after application unless the
target is very warm.)
6. Calculate the emissivity by using the equation: Emissivity=(T-B)/(R-B)
7. Measure the emissivity several times. Determine the final value by taking
an average of all measured emissivity values.
Charlie Chong/ Fion Zhang