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Read our primer article on Infrared Thermography.

Just read an article that explained emissivity and I thought it really got the point accross. For all you that use temperature as a way to guage severity of a fault you may be surprise on how accurate it really is.

Emissivity is, in fact, a material property that defines the efficiency with which a surface emits energy. Metals tend to be inefficient while non-metals are much more so. Inefficient emitters are also termed "low" emissivity surfaces. Further, low emissivity surfaces tend to also reflect their thermal surroundings.

Emissivity is typically given as a number between zero and one with zero having no emission and one have 100% emission (compared to a perfect emitter at the same temperature). Human skin, interestingly, regardless of skin tone, has an emissivity of approximately 0.98. Most shiny metals have emissivity values below 0.20.

Here's a simple experiment that clearly shows this: obtain a fry pan with a shiny metal side and a coated, non-stick side. Heat it until it is smoking hot. Put your hand NEAR the shiny side; it will feel slightly warm. Now put your hand near the coated side; it will feel VERY warm. The difference? The efficiency with which the surface emits radiation.

Infrared cameras (and infrared spot thermometers) "see" the same radiation your hand is feeling. So when I look at the shiny side of the pan, it does not look very hot compared to the coated side. Of course, both sides are the same temperature.

When thermographers are inspecting equipment with low emissivities, i.e. metals, they encounter two problems. First, the surface does not look hot when it is. Second, it is virtually impossible to accurately measure the surface temperature radiometrically. It is possible to use an "emissivity correction factor," BUT for measurements on metals, even those that are oxidized, the results will be inconsistent and inaccurate.

Despite what many people think, it is NOT simply a matter of dialing in a correction value and getting the correct temperature! If you don't believe me, try it on the frying pan ten times at varying temperatures and see what your results are. You can trust the temperature measurements on the coated side, but the shiny side will just lie to you!

One last thing: the accuracy of temperature DIFFERENCE measurements is also impacted by emissivity. It is NOT possible to make these types of measurements on low emissivity surfaces.

If you are using thermography or interfacing with thermographic data in any way, it is essential that you understand emissivity. Get out that frying pan and see for yourself!
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I find that the payback of using infrared is very high but in Canada most companies don't even have an infrared camera. Some might use a contactor like us but only once a year on electrical applications only. We do mechanical and process applications but most companies just want us to do electrical enclosures only. I can't believe that the technology that has the greatest return is the one that is least utilized. I have told clients that I would not charge them anything up front but that I would do it for 10% of everything we save them but doing infrared. They all acknowledged that we would make thousands more but they still don't have an infrared program or use infrared.
I have used Snell Infrared, ITC, Academy and Newport Solutions to instruct over 200 of my clients in the last 4 years. We promote infrared all the time but our core business is video inspection and ground penetrating radar.
I hope you use infrared and hopefully listed to what John Snell had to say. People like John have been promoting and selling infrared for years now and yes this is there business but they also have a real passion for what they do.
Good luck
I agree that it is a very under utilized tool. Like stated, most are unaware of its potential and/or they don't understand how it works to effectively use it. We have all read stories of companies abandoning their oil analysis programs because they feel it doesn't work for them but it was just they didn't understand the tests being performed or how to interprut the data. Same thing applies with IR. IR for electrical is GREAT and works wonders for finding problems and inefficiencies but it took some playing around to find other applications. I use mine for larger slow moving bearings where vibration has difficulty picking things up. I also use it on many bearing applications other than slow moving but it was a pleasant surprise to find a way to monitor those slow moving items. I also check for missing refractory in our furnaces and duct work. We can get an idea of how much work will be required before we shut down. Before it took a day or so of being shut down to determine just how much work was required, now we have an idea before we go in for inspection. Great tool but under utilized and misunderstood. It gives a 3rd dimension to failure detection.

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