Brief Talk On Thermography

Posted by Kyle Skelson on

 

Many people have assumptions when it comes to thermography, whether that being that thermal cameras can see through walls, or that thermography is just as simple as pointing a camera at something, however thermography is much more complicated than this. So what were going to do now is look at a few reasons as to why this is not the case.

 

What we need to remember when it comes to thermography, is that what we are dealing with infrared radiation. Like with most things, thermography has its limitations such as not being able to see through glass. Once we start to understand these limitations, we can then begin to get the most out of thermal equipment we are using.

 

We also need to take into account that in order for our thermal camera to see/work, it needs to be able to pick up the infrared radiation given off by that object. Now, the good thing is that anything that has a temperature above -273° or 0K (Kelvins) gives off thermal radiation. In addition to this, we need to take into account that the objects we are looking at need to have some form of temperature difference. 

 

Once we start to to understand how our thermal equipment is able to see we can then really start to become a lot more accurate in what it it is were doing. However, there are still many other things that are extremely important when it comes to thermography.

A few of these things we are going to look at now: Emissivity/Reflectivity and Reflected Apparent Temperature.

 

Emissivity/Reflectivity

Now, in the most basic terms, emissivity is the ability of an object or material to emit infrared radiation and reflectivity is the exact opposite of that. Both emissivity and reflectivity are expressed as a units and their is a basic equation that explains their relationship which is ε+ρ = 1. Based on this calculation we know that if an object has an emissivity of .95 then it must have a reflectivity of .05 as between the two we must always equal 1.

 

As a thermographer we need the objects we look at to have a high emissivity in order for us to get accurate temperature readings. In basic terms, this means that whatever we are looking at is emitting high enough amounts of infrared radiation for our thermal equipment to detect, whereas objects or materials with high reflectivity perform the opposite. So, in turn, they are deceitful when looked at through thermal cameras and this is something we need to be aware of. 

 

Reflected Apparent Temperature.

The final problem that were going to look into is something called Reflective Apparent Temperature. The Reflected Apparent Temperature is how we allow our thermal imaging equipment to compensate for the exitant radiation that is existing all around us. As previously mentioned, everything around us that is above -273° or 0K gives off radiation. Imagine all of this radiation is bouncing around off of everything and impeding our radiation that we are trying to detect from the item/object that we want to study.  This is were our Reflected Apparent Temperature comes into affect.

 

Reflected Apparent Temperature is not to be confused with the ambient temperature in a room as these are completely separate things due to the fact that Reflected Apparent Temperature can, and probably will, change depending on the plane of view that you are looking at. 

 

To conclude, based upon the few topics we have looked at, thermography and thermal imaging as a whole is a lot more technical than most people understand, yet we have only briefly touched upon the basics. 

 

If you would like to discuss anything to do with thermography or thermal cameras then please do contact us and one of our experts will get in touch.

 


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