FAG Detector III User Manual page 281

There is no risk of contamination and no mechanical effect on the surface of
the object; thus wear-free. Lacquered surfaces, for example, are not scratched
and soft surfaces can also be measured.
Having enumerated the advantages, there remains the question of what to keep
in mind when using an IR thermometer:
The target must be optically (infrared-optically) visible to the IR thermometer. High
levels of dust or smoke make measurement less accurate. Concrete obstacles,
such as a closed metallic reaction vessel, allow for only topical measurement -
the inside of the container cannot be measured.
The optics of the sensor must be protected from dust and condensing liquids.
(Manufacturers supply the necessary equipment for this.)
Normally, only surface temperatures can be measured, with the differing
emissivities of different material surfaces taken into account.
Summary: The main advantages of noncontact IR thermometry are speed, lack
of interference, and the ability to measure in high temperature ranges to 3000°
C. Keep in mind that only the surface temperature can be measured.
Infrared measuring system
An IR thermometer can be compared to the human eye. The lens of the eye
represents the optics through which the radiation (flow of photons) from the
object reaches the photosensitive layer (retina) via the atmosphere. This is
converted into a signal that is sent to the brain. Fig. 1 shows an infrared
measuring system process flow.
Fig. 1 Infrared measuring system
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