Infrared Energy And Ir Thermometer Theory - FLIR TG54 User Manual

9.2 Infrared Energy and IR Thermometer Theory
Infrared energy is part of a complete range of radiation called the electromagnetic spectrum.
The electromagnetic spectrum includes gamma rays, X‐rays, ultraviolet, visible, infrared,
microwaves (RADAR), and radio waves. The only difference is their wavelength or frequency. All
of these forms of radiation travel at the speed of light. Infrared radiation lies between the
visible and RADAR portions of the electromagnetic spectrum.
The primary source of infrared radiation is heat or thermal radiation. Any object which has a
temperature radiates in the infrared portion of the electromagnetic spectrum. Even objects
that are very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to
radiate visible light, it will emit most of its energy in the infrared. For example, hot charcoal
may not give off light, but it does emit infrared radiation, which we feel as heat. The warmer
the object, the more infrared radiation it emits.
IR Thermometers measure an object's surface temperature. The thermometer's optics sense an
object's emitted, reflected, and transmitted energy.
The TG Series translates the sensed information (targeted by the Laser) into a temperature
reading that is displayed in text on the center of the display. If the thermometer measurement
exceeds the published temperature range, the display will indicate OL.
The amount of IR energy emitted by an object is proportional to an object's temperature and its
ability to emit energy. This ability is known as emissivity and is based on the material of the
object and its surface finish. Emissivity values range from 0.1 for a very reflective object to 1.00
for a flat black finish.
The TG Series has both adjustable and preset emissivity settings. There are four (4) presets and
an adjustable emissivity span from 0.10 to 0.99. See the Appendix for a list of common
materials and their respective Emissivity factors. Access the Programming menu (covered in
Section 6) to set the desired emissivity factor.
FLIR TG54_TG56 User Manual
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Document Identifier: TG54_TG56‐en‐US_AA