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Emissivity

21/11/2012 by SLS

Emissivity or in shorthand ε or e is a percentage of how much heat an item can radiate as compared to a black body (1.0). A low value indicates low emissivity while a higher value indicates a higher emissivity – the higher the number the more accurate a temperature reading you can get with an infrared camera. There are 5 main factors that effect an object or materials emissivity:

  • The material itself (Black hole box – near perfect emissivity 1, human face .98, black electrical tape .95, copper .02 to .6, etc…)
  • The surface (Rough, Polished, etc…)
  • One’s angle of view (while you should not be looking directly at the item, you should be as straight onto it as possible – i.e. standing 5° off to the side)
  • The temperature (while rare, the hotter metal gets, their emissivity can increase to the point of showing up in the visible spectrum)
  • The wave length (Mid or Long – see FAQ’s for chart)

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