Thermography and Infrared Light
Normally, our vision is limited to a very small portion of the electromagnetic spectrum. Thermal energy has a much longer wavelength than visible light. So long, in fact, that the human eye can’t even see it, just like we can’t see radio waves.
Infrared radiation is electromagnetic radiation with longer wavelengths than those of visible light, and is therefore invisible to the human eye. It is sometimes called infrared light. It extends from the nominal red edge of the visible spectrum. Most of the thermal radiation emitted by objects near room temperature is infrared. A “long wave” infrared camera which is good for typical infrared applications will normally operate in the wavelength range of 7-14 microns
With thermal imaging, the portion of the spectrum we perceive is dramatically expanded, helping us “see” and “measure” thermal energy emitted from an object. Unlike visible light, in the infrared world, everything with a temperature above absolute zero emits heat. Even very cold objects, like ice cubes, emit infrared. And visible light doesn’t affect the thermal world, so you can see equally well in highly lit and totally dark environments.
The Electromagnetic Spectrum
The higher the object’s temperature, the greater the IR radiation emitted. Infrared allows us to see what our eyes cannot. Infrared thermography cameras produce images of invisible infrared or “heat” radiation and provide precise non-contact temperature measurement capabilities. Nearly everything gets hot before it fails, making infrared cameras extremely cost-effective, valuable diagnostic tools in many diverse applications. And as industry strives to improve manufacturing efficiencies, manage energy, improve product quality, and enhance worker safety, new applications for infrared cameras continually emerge.
How does an Infrared camera work?
An infrared camera is a non-contact device that detects infrared energy (heat) and converts it into an electronic signal, which is then processed to produce a thermal image on a video monitor and perform temperature calculations. Heat sensed by an infrared camera can be very precisely quantified, or measured, allowing you to not only monitor thermal performance, but also identify and evaluate the relative severity of heat-related problems.
Recent innovations, particularly detector technology, the incorporation of built-in visual imaging, automatic functionality, and infrared software development, deliver more cost-effective thermal analysis solutions than ever before.
Why measure temperature?
Finding a problem with an infrared camera is sometimes not enough. In fact, an infrared camera image alone without accurate temperature measurements says very little about the condition of an electrical connection or worn mechanical part. Many electrical targets are operating properly at temperatures that are significantly above ambient. An infrared image without measurement can be misleading because it may visually suggest a problem that does not exist.
Infrared cameras that incorporate temperature measurement allow predictive maintenance professionals to make well informed judgments about the operating condition of electrical and mechanical targets. Temperature measurements can be compared with historical operating temperatures, or with infrared readings of similar equipment at the same time, to determine if a significant temperature rise will compromise component reliability or plant safety.
What is Emissivity?
Emissivity is the ability of a surface to emit radiant energy compared to that of a black body at the same temperature and with the same area.
The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation which is not visible to human eyes.
Quantitatively, emissivity is the ratio of the thermal radiation from a surface compared to the radiation from an ideal black surface at the same temperature. The emissivity ratio varies from 0 (perfect reflector) to 1 (perfect emitter).