Infrared (IR) (thermal) cameras, how to use for education and profit

Describe and/or review kits and lab equipment.
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shawn
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Infrared (IR) (thermal) cameras, how to use for education and profit

Post by shawn »

A quick guide to using and teaching about infrared cameras.
Far IR image of author
Far IR image of author
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The photographer facing "clear" glass will get a self-portrait. This shows how taking an IR picture of glass does not show much about the glass, it shows a reflection of something usually irrelevant to a heat-study. To show trainees how undependable images of glass are, take two pictures looking at the same glass, with some other materials around it, from different angles. Between the two pictures, the surrounding non-glass will look the same and the will should look different. The same goes for shiny metal, which acts in IR just like it acts in visible colors. However, the glass/metal is emitting some energy in IR, so what we're seeing is a combination of reflected and emitted radiation—Only by careful analysis can the two be separated. Right now I'm looking at my beige file cabinet—I can tell it's beige, yet because it's glossy I also see in it the reflection of a blue book. See the next photo of a couple windows in the winter.
Far IR image of exterior of house in winter
Far IR image of exterior of house in winter
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Streaks of air of a different temperature, usually around doors and windows, easily show infiltration. See this photo of floor cooled by air streaming under a door.
Far IR image of floor cooled by air infiltration
Far IR image of floor cooled by air infiltration
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An IR camera can be used like an IR temperature gun. There's a temperature estimate given for the spot in the middle of the field of view. If trainees have used a temperature gun before, focus on taking recognizable images, like of people's faces, to shift their thinking towards imagery.
IR cameras use false color to represent the spectrum. Have trainees switch back and forth frequently between the different color schemes in the camera so they don't make the model the reality.
The point of an image rather than a single temperature point is to see differences instantly. A single temperature of a wall, also knowing the inside and outside temperature, can tell you something about the R-value of that wall. An IR photo can tell you where the wall is failing, or whether cavities in the wall have insulation in them or not.
Insulation is misperceived as something that keeps things warm. Better to think of it as something that slows the movement of energy from a warm area to a cold area, thus keeping colder things from warming faster and warmer things from cooling faster. An energy bill isn't just for keeping a house at a certain temperature, it's for countering the cooling/heating that's happening to a house because of whatever temperature difference. Ask trainees what they think of putting a blanket on an ice cube.
Air leaks are the easiest things to see with an IR camera, but with a better knowledge of physics, one can tease out more subtle messages about radiation and conduction, the other two ways heat can transfer. Mainly, one goes around inside taking pictures of air leaks, and one takes larger pictures outside to see how the house transfers energy via radiation.
Say there is an air leak. The direction of the air movement, be it inwards or outwards, will create opposite effects in an image. This can be confusing if there aren't telltale streaks showing the direction.
The cameras are usually set to automatically adjust the range of temperatures represented by the false-color spectrum, but when one wants to make quick comparisons in the field they should set the camera to a single range.
Sunlight may play tricks with your interpretation of an image of an exterior. Auditors prefer cloudy days.

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