Let me break down the differences between heat and temperature as best as I can...Once you can understand the differences, you will have figured out a large portion of what infrared thermography is all about.
Heat is a form of energy that is transferred by a difference in temperature. It is not energy contained within a system (or bodies) like we like to think of it as.
Temperature is a measurement of the average kinetic energy (motion energy) of the molecule in an object or system. It is NOT energy...it is the result of adding or removing heat energy. Below, I post a diagram that I found helpful when I was trying to understand these concepts.
An example of how heat transfer works can be illustrated by the image on the left. This is an image of a wet roof that is leaking into a ceiling. We are able to see this because the transfer of heat energy is what causes the cooling effect of evaporation. The infrared camera is able to spot wet areas because of the change in temperature. Pretty cool right?! Not so much for the people that have to take care of this roof though...
Someday we will talk about how roof inspections work and when the best time to do them is. Timing is a huge part of thermography and knowing when to do your scan can make a huge difference.