About Infrared Thermography
What is Infrared Thermography?
Infrared Thermography involves the use of an infrared imager, commonly known as thermal cameras, to “see” and “measure” invisible infrared energy being emitted from an object. The thermal image produced from the IR camera is called a thermogram.
Infrared radiation occurs in the long-infrared range of the electromagnetic spectrum (9,000–14,000 nanometers or 9–14 µm). Since infrared radiation is emitted by all objects with a temperature above absolute zero according to the black body radiation law, thermography makes it possible to see one’s environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature.
When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to the military and other users of surveillance cameras.
Thermography has a long history, although its use has increased dramatically with the commercial and industrial applications of the past fifty years. Firefighters use thermography to see through smoke , to find persons, and to localise the base of a fire. Maintenance technicians use thermography to locate overheating joints and sections of power lines, which are a sign of impending failure. Building construction technicians can see thermal signatures that indicate heat leaks in faulty thermal insulation and can use the results to improve the efficiency of heating and air-conditioning units.
Electrical thermography has rapidly gained global endorsement amongst plant and facility management as an integral aspect in their Condition Monitoring, Predictive and Preventive Maintenance programs.
Energy loss, especially form structure, has been highlighted in the latest building codes and faulty refractory or insulation in industry adds to the outlay for energy, increasing consumption and raising the cost of products. There is no better inspection technique than Infrared Thermography to find these thermal anomalies.
Why Infrared Thermography?
As a “thermographer”, taking thermal images may seem easy: simply “aim, focus, shoot” – and you get your thermal image! However, the true value lies in what one understands about the object of interest, how it operates, the heat transfer within and to the surface of the object, how to adjust the camera to include maximum thermal detail. Most importantly, it boils down to the Thermographer’s ability to analyse the thermogram, interpret the thermal data appropriately to identify thermal anomalies as existing or potential problems or faults. Finally at end, document and present the work done and findings in a clear and concise report.
No, this is no simple task of just “aim, focus and shoot”, as most camera manufacturers and vendors would reiterate to you.
Many thermographers still grapple with the issues of
- Reflected images (that are easily confused with or mistaken as a “hot-spot”) and
- the impact of “emissivity” of different objects within thermal images.
Equally worrisome is that many “certified” thermographers were taught the “old-school” “DeltaT” approach towards analysis of thermal data (i.e. simply taking the temperature differential between the lowest and hottest spot – as a means of determining the “severity” of an thermal anomaly). This is not an appropriate basis, especially within the context of electrical IR applications, by which our Institute has strenuously distance itself from. At IIRT’s training, you are assured of our full guidance on the appropriate approach!
“The use of Infrared Thermography (IRT) using measurements of surface temperature to monitor condition and diagnose faults in civil, mechanical and electrical systems has become a key activity in predictive maintenance programmes for most industries. The effectiveness of these programmes depends on the capabilities of individuals who perform the measurements and analyse the data.
Certification to this specification will provide evidence of the qualification and assessment of individuals to perform Infrared Thermography measurements and analysis using appropriate sensors and equipment. eg. (UK) BINDT- PCN CM/GEN.
At IIRT, we strive to instil the need for being alert, observant and maintaining an inquisitive mind-set in each participant. We structure our tutorials with an extensive mix of video presentation and illustrative real-world thermal images that will help participants gain effective understanding on each topic of study. Special guidance is attention is rendered on the Do’s and Don’t’s in Report Writing, in preparing a clear, concise and meaningful report.
IIRT’s unique brand of IR training: CONSISTENTLY RATED “10/10” and “EXCELLENT” by participants, course after course… your best assurance!
How it works?
In the most basic of terms, thermal imaging allows you to see an object’s heat radiating off itself. Thermal cameras are equipped with “detectors” that record the level of radiation emitted from the surface of an object. The radiant energy passes through the optics of the camera and the detectors converts this energy into an electrical output from each detector pixel. The electronic output is displayed as a two dimensional image usually on an LCD viewing screen although some cameras also have a viewfinder.
Specialised thermal imaging cameras use focal plane arrays (FPAs) that respond to longer wavelengths (mid- and long-wavelength infrared). The most common types are InSb (Indium Antinomic), InGaAs (Indium Gallium Arsenide), HgCdTe (Mercury Cadmium Telluride) and QWIP (Quantum Well Infrared Photodetector) FPA. The newest technologies use low-cost, uncooled microbolometers as FPA sensors. Their resolution is considerably lower than that of optical cameras, mostly 160×120 or 320×240 pixels, up to 1280 x 1024 for the most expensive models. Thermal imaging cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted due to the military uses for this technology. Older bolometers or more sensitive models such as InSb require cryogenic cooling, usually by a miniature Stirling cycle refrigerator or liquid nitrogen.
The thermal imaging camera would next employ a series of mathematical algorithms. Since the camera is only able to see the electromagnetic radiation that is impossible to detect with the human eye, it will build a picture in the viewer and record a visible picture, usually in a JPG format.
The presented image is called a “Thermogram” and it displays the energy levels as either Black & White (Grayscale) or series of false colours, as a two dimensional image. Most cameras offer a selection of different colour palettes that may best suit a particular application. Some thermal cameras use a grayscale instead. Police helicopters, for instance, use a greyscale to make suspects stand out.
The features and price of a thermal camera is greatly dependent on its specifications, in particular, the number of detectors built-in. Entry-level models typically offers 160 x 120 pixels, the higher end models – equipped with 1280 x 1024 pixels. The choice of using a thermal camera depends greatly on the area of the intended application and in all practicality – the budget for such an acquisition.