How Your IR Thermometer Works

How Your IR Thermometer Works

Tuesday, December 27, 2016



There’s something about an IR temperature gun which piques my curiosity. The fact that it’s possible to read temperature, without physically touching the source can be confounding while traditional thermometers seem much less mysterious. Perhaps this is why they can be so much fun (or maybe it’s the whole Predator thing). We know that their ease of use, quick response, and ability to measure hard to reach places make them versatile and powerful measurement tools, but how do they actually work?

To be clear, IR thermometers actually do not measure heat directly, they measure light. Infrared light is invisible to humans; our eyes simply cannot perceive wavelengths longer than red visible light. The reason why infrared light is used to measure heat is because nearly everything emits infrared radiation, which is one of the ways heat is transferred. Despite our inability to see this light wave, we sense it every day as heat.


Just like visible light, infrared light can be reflected and in this way, “channeled” to the IR gun’s detector. This detector converts the thermal reading into an electrical signal. In theory, the higher the infrared radiation, the higher the molecular activity and temperature.



Since the light is being funneled into the detector, its accuracy depends in part by the distance from the object being tested. The farther you are from the object, the more difficult it is to get a precise measurement because your increased area of measurement is taking in infrared emission from other surfaces.

Another thing to consider is an objects emissivity. The emissivity of an object describes its ability to emit thermal radiation. Much of this reading has to do with the reflective quality of the object. Emissivity is measured between the values one and zero, one being that of a truly black and totally absorbing material, the farther away from that value, the higher the reflection and if you do not account for it, the less accurate your reading will be since much of the reading will have been reflected. So, now that you have some insight as to how the IR thermometer works, consider some of its many applications and see if this versatile tool is right for you!

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