Understanding Infrared Thermography Reading 3

Bccause most quantitative thermographic instruments measure radiant
energy values converted to temperature readings by a computer, calibration
information is usually stored in the computer software and is identified with a
specific instrument serial number. If a specific instrument calibration is not
available in the software, the computer will usually default to a generic
calibration for that class of instrument. In addition to a blackbody calibration,
the software is usually provided with correction functions for ambient effects
such as atmospheric attenuation as a function of working distance and for
emissivity correction.
Default settings for these values are normally in effect unless the operator
chooses to alter them. Checking calibration of a thermal imaging system in
detail requires placing a blackbody reference source in front of the instrument
so that ilt subtends a substantial area in the center of the displayed image
(much greater than the instantaneous field of view). The correct measurement
conditions must be set into the computer where applicable [example. working
distance = 10 m (33 ft), ambient temperature = 25 °C (77 ° F), emissivity = 1,
etc.] and the temperature reading compared to the reference source setting.
The spot measurement software diagnostic should be used if available. The
detailed calibration should include the widest range of temperatures possible.
Charlie Chong/ Fion Zhang