Figure 1.

 

Thermography Explained

 
Thermography is the science of imaging radiated heat. All objects above absolute zero radiate heat. Heat radiation itself is part of the electromagnetic spectrum, which includes radio, TV, light and X-rays. Figure 1 shows how the spectrum is arranged and where infra-red is situated just below visible light. The part where Thermal Imaging Cameras operate is long wave infra-red, in the range of 7.5 um to 14 um. The actual temperature range 'seen' with our cameras is -20 oC to +600 oC, the temperature measurement accuracy is +-2 oC and thermal sensitivity is ≤ 0.045 oC.
 
It is the ability to sense radiated heat, which itself is a function of incident heat (the heat of the object) + transmitted heat (influenced from surrounding heat sources) + reflected heat (like a mirror, surrounding heat sources reflected from the object). By understanding the interaction of heat energy on the object being observed, it becomes possible to apply thermal imaging in all sorts of applications. 
 
For instance, in the case of underfloor buried heating pipe, it is the conduction of heat from the source (in this case the pipe work) through the screed and finally seen as radiated heat via the thermal camera. It is not the pipe work seen directly, but a result of surface radiation which in turn is effected by the materials used (ceramic tiles give a clear image, wood flooring less so, followed by carpet etc). Therefore an understanding of Thermography is required to be able to obtain consistent and useful information.
 
In the case of Electrical distribution boards and components, Thermography is an excellent method for quick and non-invasive means to determine the condition of terminals, switchgear, components, Fuse / MCB boards etc. Where a failure is occurring, heat is normally a consequence. i.e loose terminals lead to increased resistance and a rise in temperature. A thermal inspection will quickly visualise this fault before any physical evidence appears, thus avoiding costly downtime and repair. An understanding of both Thermography and Electrical principals is required to establish whether the heat rise is a function of increased load on a component or a potential fault developing. 
 
It can be seen therefore that a Thermographers experience in all fields of engineering is desirable to provide a professional service to our clients.