How do thermal cameras work?
Unlike your iPhone’s camera, thermal cameras take pictures of invisible infrared radiation. This radiation is also known as infrared light and is given off by all objects. The hotter the object, the more infrared light is emitted and then measured by a thermal camera. These specialised instruments are widely used in the building industry and in facilities management for such applications as building, pest or electrical inspections. So, how do they work and how do you find the right model for your needs?
About Thermal Cameras
Thermal cameras are specialised sensors that measure the heat radiating off an object. This radiation is captured and then displayed by the camera using either a full-colour scale or a greyscale. Each thermal camera has its own scale along with a key you so can interpret the camera’s readings.
Colour scales indicate cooler temperatures in shades of blue, purple or green. Warmer temperatures are assigned yellow, orange or red tones. Greyscales will usually show lighter greys and whites for warmer temperatures, while darker greys and blacks represent less heat.
Check out the example of my morning cup of coffee. Using the colour coded heat scale on the right side as your reference, you can clearly see the heat radiating from the hot liquid, whilst the surrounding areas are much cooler. (I think I’ll let it cool down a few degrees before taking a sip!)
What’s the magic behind Thermal Cameras?
The electronics and processes that support these instruments can be summarised in three steps:
1. When your camera is pointed at the object or surface you wish to measure, a special lens within the camera will capture and focus all the infrared light being emitted within your camera’s field of view.
2. The infrared light is then directed from the lens onto a detector chip, often known as a sensor array. This chip contains many thousands of pixels arranged in a grid formation.
3. Each pixel within the sensor array reacts to the infrared light it receives to produce an electronic signal.The electronic signal from each pixel is then sent to a processor which converts the intensity and pattern of the signals from the sensor array into a scaled map known as a thermogram – and this is the thermal image you see!
While these steps may sound complex and possibly time-consuming, don’t worry. It all happens almost instantly so you can gain a quick and accurate representation of the temperature map of those objects you wish to observe.
Uses for thermal cameras
The applications for thermal cameras are numerous. Here’s a list of the most common applications that the scientists at Instrument Choice encounter when responding to requests for advice:
- Building Inspections – Troubleshooting and locating the sources of building faults or inefficiencies. Examples include energy waste due to poor design or construction, locating unwanted moisture in a structure, or detecting electrical faults.
- Pest Inspections – Track the heat signature of pests in hidden locations such as wall cavities, ceiling voids and stored commodities.
- Electricians – Check breaker boxes for loose connections, detect fuse or wire overloading and monitoring vital equipment for overheating.
- Preventative Maintenance - Examples include monitoring HVAC systems, checking seals on machinery for leaks and checking for unexpected heat friction within machinery.
How to find the right Thermal Camera for your application
The two critical things to consider when purchasing or using a thermal imaging camera are resolution and sensitivity. What do you need to know?
- Resolution – Resolution refers to the clarity of the image produced by your camera. It’s directly related to the number of pixels in your camera’s sensor array. Simply, the more pixels, the higher the resolution. There are three standards for thermal camera resolution:
- <160 x 120 (19,600 Pixels – Low resolution)
- 320 x 240 (76,800 pixels – Medium resolution)
- 640 x 480 (307x200 pixels, High resolution)
The minimum amount of resolution you require is determined by your application. For example, if you’re working on high-risk, precision or expensive items (such as electrical equipment), and you need to investigate objects closely, you may need a higher resolution camera that will give you clear images when using your camera’s zoom function. Lower resolution cameras may still let you zoom-in but your subject may appear blurry.
2. Thermal Sensitivity – This describes the sensitivity of your camera to contrasting thermal zones over time.The more sensitive a thermal camera, the more definition you will see between hot and cold boundaries. The lower the sensitivity the more blurring will get between hot and colour boundaries. If you need to account for incremental heat variations or you need more accurate temperature profiling you should look for a more sensitive device.
The specification for sensitivity is known as NETD or the ‘Noise Equivalent Temperature Difference’.The NETD scale is expressed in milli-Kelvins (mK). The higher the NETD, the less sensitive the camera is to contrasting temperatures, the lower the NETD the more thermal definition you’ll get in your camera’s images.
Examples of thermal cameras
Our scientists have put together a few thermal camera examples with varying specifications to show some of the huge range of cameras available.
FLIR Spot Thermal Camera .jpg?Action=thumbnail&algorithm=fill_proportional&width=136)
Product Code: IC-FTG165
This thermal camera is a perfect entry-level device. Simple to use, rugged and reliable, it’s a popular choice for troubleshooting and detecting building, electrical or maintenance issues.
Resolution: 80 x 60 (4,800 pixels)
Sensitivity: 150mK
FLIR C2 Compact Professional Thermal Camera
Product Code: IC-72001-0101
The FLIR C2 is pocket-sized and jampacked with features. It’s widely used for building, electrical and mechanical applications.
Resolution: 80 x 60 (4,800 pixels)
Sensitivity: 100mK
Testo 865 Thermal Imager 
Product Code: IC-0560 8650
The Testo 865 can distinguish temperature differences as low as 0.12°c. It’s a go-to device if accuracy and sensitivity matters.
Resolution: 320 x 240 (76,800 pixels)120mK
Sensitivity: 120mK
Testo 872 Thermal Imager 
Product Code:IC-0560 8721
For the ultimate support in professional industrial or building settings, this thermal camera takes quick, reliable and accurate images. Complete with incredibly high resolution and excellent thermal sensitivity this camera can detect temperature differences as low as 0.06°C!
Resolution: Extendable from 320 x 240 (76,800) to 640 x 480 (307,200 pixels)
Sensitivity: 60mK
Conclusion
If you’re a professional building inspector, pest controller or tradesperson a thermal camera will help you remove the guesswork when troubleshooting or undertaking preventative maintenance.
Want more examples of Thermal Cameras? You can find many more on the Instrument Choice website.
Have questions or want some help finding the right thermal camera for your application? Not sure what combination of sensitivity and thermal resolution you need? Call one of our helpful scientists on 1300 737 871 or email [email protected] and they will answer all your questions within three business hours.
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