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“Infrared thermography is the science of acquisition and analysis of thermal information from non-contact thermal imaging devices”

What this means in real life is that a camera specifically designed to see infrared takes a ‘photograph’ of the heat emitted by the target.

Only a few years ago this meant that the camera’s support electronics had to be installed in a vehicle with the camera mounted on the vehicle roof. Presumably the engine had to be running to provide the required power!

About 5 years ago cameras were shoulder mounted, much like the TV cameras of the 1980’s.

Now the latest cameras are only a little larger than the current home video cameras - but they are the price of a new luxury motorcar.

Below is a representation of the electromagnetic spectrum showing the small ‘visible’ part of it that we can see. The infrared part of the spectrum sits between the visible part and the microwave part.

There are some dangerous parts of the electromagnetic spectrum, the frequency that microwave ovens use is selected because it excites the water molecules in food, and is therefore dangerous to us as we are composed largely of water. Too much exposure to X-rays can be dangerous and so can too much exposure to radioactive sources.

The infrared that we look at with the cameras sits just below the visible part and in terms of energy, we can see very small amounts. The new cameras can see a very small temperature change (0.08’C) and very small differences in the energy emitted by the targets.

This allows us to see the world in a totally different ‘light’  

Would you find you car if they looked like this….(no visible spectrum colours as we know them)

                       Or would you recognise your friends if they looked like this to you?

The world of infrared opens up new and exiting possibilities that cannot otherwise be seen.

There are laws governing thermodynamics but these are outside the scope of this article. The laws governing heat and light have important differences, which we can exploit to ‘see’ other things.

We can utilise the ‘thermal capacity’ of materials to ‘see’ through things. Consider a large tank half full of liquid. The liquid has a higher thermal capacity than the air above it. Therefore it will take longer to heat up and cool down. If we let the heat of the sun heat up the tank and contents and then wait for the sun to go down, the metal tank and the air in the tank will loose heat quicker than the liquid allowing the heat radiated by the liquid to be seen through the tank, showing us the level inside.

Another use of thermodynamics - heat will travel along a conductor such as a metal girder to transmit heat to the outside of a building. Wood has conductivity some 400 times less than metal and so will not conduct heat as readily. An infrared camera therefore needs to know what it is looking at to make proper measurements.

The thermographer needs to be able to interpret these images correctly, taking into account many factors not discussed here, to make informed conclusions and meaningful reports.