Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

To perform this function, the unpowered device is heated sequentially to two
known low-level temperatures, and the stored thermal images are used to
allow the computer to calculate emissivity of each pixel. The device is then
powered and the image produced is corrected, point by point, for the
emissivities previously computed. There is great interest in applying this
spatial emissivity correction to larger targets such as circuit cards. The
difficulty in developing a reliable emissivity matrix lies in achieving tight
control over the temperature and temperature uniformity while heating a
target of this size.
For the professional thermographer, the maintenance of an historical
database is most critical, and thermography software allows this to be done
systematically. The historical data included with stored images (time, date,
location, ambient conditions, distance to target, estimated effective emissivity,
scanner serial number, and additional stored comments) serve as important
inputs and subsequent backup for the written report. New software to aid the
thermographer in the efficient and rapid preparation of professional looking
reports is also available from most manufacturers of thermal imagers (see
Section 2).
Charlie Chong/ Fion Zhang