General IRTC40 Mode D'emploi page 4

surface relative to surfaces around it.
Engineers call this difference T, and
understanding T is the key to using the
scanning function of the IRTC40.
Another way to think of T is as one-half
the width of a temperature "window"
centered on a reference temperature. As an
example, for a reference temperature (Tref)
of 75°F, choosing a T of 5°F would
establish a temperature window that spans
the 10° difference between 70° and 80°.
Any surface cooler than 70° would fall
below the cold edge of the temperature
window. Any surface hotter than 80° would
fall above the hot edge of the window.
What the IRTC40 does extremely well and
quickly is to place scanned targets into one
of three color-coded categories: green for
targets within the temperature window (Tref
plus and minus T), red for targets hotter
than Tref plus T, and blue for targets
cooler than Tref minus T. The instrument
simultaneously uses sound to categorize
scanned targets by temperature. Targets
colder than the reference temperature ± T
generate a slow beeping sound and a
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