Top considerations when buying a thermal imager

Sat Sundhu
October 06, 2017
By Sat Sundhu
For better-quality images, you need more detector pixels properly focused on the target.
For better-quality images, you need more detector pixels properly focused on the target. Courtesy Fluke
October 6, 2017 — Not all thermal imagers (a.k.a. infrared [IR] cameras) are created equal. While advertisements and promotions may present specifications that, at first glance, make imagers seem like one and the same, many factors make up a quality thermal imager—one that can withstand the rigours of day after day work in harsh environments.

The next time you’re shopping for a thermal imaging camera, it’s a good idea to closely compare specs, features and quality of construction. It can spare you from making the wrong choice and ending up with a camera that will give you no more than an entertaining view in infrared, rather than a professional tool you can use daily in industry.

Lower-quality thermal imaging devices tend to be breakable and un-rated in drop tests. While those imagers may look the part, they often impersonate industrial-worthy tools, as they tend to lack adequate image resolution and built-in battery monitoring, and require a cumbersome workflow to collect and save image data.

Professional tools are rugged, long-lasting and save you time. In addition, a professional tool will be able to focus and capture images through IR windows. When properly installed, these windows provide a safer and time-efficient way to inspect electrical equipment by virtually eliminating the need to open cabinet doors.

Look for the following features to ensure you end up with an imager that’s up to the task.

Ruggedness, survivability and form factor

Lower-quality IR cameras often cannot withstand repeated use or even an accidental tumble. Tools designed for professionals, however, should be tough enough to operate in harsh environments. Considering a manufacturer’s reputation for quality construction is an important factor when evaluating products.

When I talk about ruggedness, it’s more than expecting the unit to work after being dropped on the floor. The build quality is important, down to the most minute details. How well does the snap on the battery door close? Does the camera’s handle have an ergonomic grip with good weight distribution? Does the lens cover provide the right amount of protection?

Different focus options

A blurry IR image can give you data that may not truly reflect the appropriate level of criticality of the components under inspection. Fixed-focus cameras offer point-and-shoot technology that are generally in focus on targets at a certain distance and beyond. Performing scans with fixed-focus is often faster than with manual focus, but can be less precise.

With a higher-resolution product, the ability to precisely focus the camera becomes critical. Cameras with adjustable or manual focus can focus much closer to the target, often from 15 cm (6 in.) and beyond. They can also obtain much sharper images and more-accurate results from further distances. For even more precision, some infrared cameras come with a built-in laser pointer to help pinpoint your exact image target.

Blended visible light and infrared images

Infrared cameras that combine visible light and infrared images allow operators to quickly locate and identify potential problems. Essentially, this means the camera blends the two images together, pixel for pixel, in a single display, making it easier to see the source of a heat issue. This feature automatically captures a digital visible light image at the same time as an IR image. A technician using the camera can then view the image in full infrared, full visible light or in several degrees of blending.

Battery life and monitoring

A thermal imager should allow you to monitor your battery charge to avoid unexpected power loss. The best thermal imagers use rechargeable lithium-ion batteries, which provide high energy density and are slow to discharge. In addition, Li-ion technology typically delivers a 5-year operating life, and often can be recycled. To maximize the life of Li-ion packs, a good rule is to use them to full discharge then fully recharge them the first 5-10 times.

Advanced diagnosis and reporting software

Software helps enhance and clarify images, adds analysis and empowers teams to share professional-looking reports across different applications and industries. Software can be used as a tool to analyze, enhance and fine-tune thermal images before sharing with managers. Robust software allows users to make adjustments to optimize image quality and display findings with features like multiple image formats, ability to combine visible light and IR images, and custom reports.

Wireless image upload and sharing

Viewing thermal images from your camera on your smartphone or computer can be an important factor, depending on the work you do. Wireless sharing can save time by showing potential issues to clients or offsite co-workers. This can enable faster decision-making and real-time collaboration. Wasting time on frequent back-and-forth trips to your shop is not how you want to spend your day.

Image quality to see issues clearly

The focus of an infrared camera directly affects the accuracy of the temperature measurement calculation data that is captured. An out-of-focus image can produce a temperature measurement that is off by 20 degrees or more. For better-quality images, you need more detector pixels properly focused on the target.

Field-of-view (FOV) is the area the imager sees at a given moment. Naturally, a camera with a wider FOV displays a larger area. When two cameras operate with the same detector resolution, but one has a tighter FOV, the latter will typically produce images with more detail.

Robust memory

As anyone with a digital camera knows, images can use up memory in a hurry, so look for an IR camera with sufficient onboard memory for your needs. Going further, it’s better for a camera to have gigabytes-worth of memory storage for maintaining a database of thermal images that can be used for consistent and comparative machine diagnoses over time.

Also consider that you may be in the field for extended periods and unable to upload until later. A removable SD card allows you to have easy access to saved images, as well as extra storage.

Infrared window compatibility

Some IR cameras have such limited capabilities that their resolution and FOV might not be suitable for capturing a good image or apparent temperature data through infrared windows. IR windows are built to exacting specs and special materials that allow thermal imagers to capture images of energized equipment through a port installed in an electrical cabinet door. Since the images are taken without opening cabinet doors, the windows provide a far safer working environment—a solid barrier between the thermographer conducting an inspection and the live conductors.

These windows also make inspecting equipment more efficient. But the camera’s resolution, and particularly the FOV, must still be capable of handling the correct angle to capture the information you need for a valid inspection, so keep that in mind when shopping. Some lesser cameras may not have a wide-enough FOV, so it’s a good idea to research that spec before purchasing.

When shopping

When looking for an infrared camera to serve your electrical needs, it’s a good idea to first determine your applications, then look for a camera that suits them. Like many types of equipment, you often get what you pay for, so make sure you compare features and specs to ensure the camera you buy meets your needs for many years to come.


Sat Sandhu is a thermography services manager for Fluke, covering Europe, the Middle East and Africa (EMEA), and Asia Pacific. Sat has worked in electronics design and thermal imaging for over 36 years. Visit fluke.com/infrared.

* This article also appears in the October 2017 edition of Electrical Business Magazine. Check out our ARCHIVE page for back issues.

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