Buyer’s Guide for Thermal Cameras

What is an infrared camera used for?

Thermal imaging is an incredibly flexible and non-invasive technology that plays a crucial role in various industries. By capturing infrared radiation, these cameras allow us to keep an eye on and manage temperature-sensitive processes, whether it’s in cold chains or in high-heat environments like glass and metal production. Spotting thermal anomalies with accuracy not only enhances quality and safety but also boosts efficiency, cuts costs, and enables early intervention—even in rapidly changing industrial settings.

In the manufacturing world, infrared cameras are commonly used to monitor the temperature of metal, glass, and plastic products. The precise temperature data feeds directly into process control systems, helping to minimize waste, ensure consistent quality, and ramp up production rates. Today’s online infrared cameras offer continuous monitoring without any physical contact, automatically analyzing thermal data to trigger alarms or adjust processes whenever something goes off track.

Thermal imaging is also a game-changer for inspecting mechanical systems. It can uncover signs of friction, overheating, misalignment, or bearing wear before these problems escalate into major breakdowns. This proactive approach to maintenance planning helps reduce downtime and extends the lifespan of equipment.

In the energy sector, infrared cameras are vital for monitoring the condition of electrical infrastructure like transformers, switchgear, and overhead lines. By detecting unusual heat signatures—caused by overheating connections, imbalanced loads, or other faults—operators can tackle issues early, prevent failures, and enhance grid reliability.

When it comes to early fire detection, thermal imagers can spot hotspots and potential fire sources long before flames or smoke become visible. With their broad field of view and high sensitivity, they can monitor large areas and trigger alarms much faster than traditional smoke detectors, providing a crucial time advantage in preventing fire damage.

How does an infrared camera work?

Unlike traditional cameras that capture visible light, thermal cameras work in the infrared spectrum—because every object above absolute zero gives off thermal radiation. In a thermal imaging setup, an optical lens directs this radiation onto a detector array. Each pixel in that array represents a specific point in the scene, recording how much infrared energy is coming from that spot. Depending on the wavelength range, the detectors might use various technologies, like uncooled microbolometers or cooled infrared photodetectors.

When infrared radiation hits the detector, it changes the detector’s electrical properties. These changes are then transformed into electronic signals, which get amplified, digitized, and processed by the camera’s electronics. In uncooled systems, an internal shutter regularly corrects for offset and non-uniformity to keep things accurate. The camera’s software, using calibration data, converts the processed signals into temperature readings. This enables precise, non-contact temperature measurements—great for monitoring, analysis, and automated alerts.

Thermal cameras come in different spectral ranges, temperature ranges, frame rates, sensitivities, and resolutions, offering a wide array of performance and price options. This variety ensures that there’s a suitable model for nearly any industrial need. The following sections will highlight key factors to consider when choosing an infrared camera that best meets the requirements of specific applications.

Step 1: Select the optimal spectral range of the infrared camera.

Every object that’s warmer than absolute zero gives off electromagnetic radiation from its surface, and the hotter it gets, the more intense that radiation becomes. As this radiation moves through the atmosphere, some of it gets absorbed or scattered, while other parts make it through. The atmosphere’s ability to let this radiation pass varies quite a bit depending on the wavelength—there are areas of high absorption that alternate with “atmospheric windows” where transmission is much better.

For measuring temperature without contact, we typically use infrared wavelengths that range from about 0.5 to 14 μm. This range includes a variety of electromagnetic waves that can be categorized into short-, mid-, and long-wave infrared bands, each with unique measurement properties and uses.

So-called ideal blackbody radiators emit the maximum possible infrared energy at every wavelength without reflection or transmission. Few bodies meet the ideal of a black body. Many bodies emit far less radiation at the same temperature. The infrared sensor receives the emitted radiation from the object’s surface, reflected radiation from the surroundings, and potentially infrared radiation transmitted through the blackbody.

Many non-reflective materials tend to have a high and fairly consistent emissivity, which doesn’t change much with surface conditions—especially in the long-wave infrared range. In contrast, metals usually exhibit low emissivity that varies significantly based on their surface finish, and this emissivity often drops at longer wavelengths. As a result, you might encounter inconsistent or unreliable measurement outcomes.

To get accurate readings, it’s crucial to measure infrared radiation within a wavelength and temperature range where the material has a relatively high emissivity. So, picking the right spectral range is a vital step when choosing an appropriate temperature measurement device.Additionally, measurement should always be preferred in the short-wave range. According to Planck’s radiation formula, the highest radiation intensity is emitted in general; secondly, metals, for example, also have the highest emissivity.

Therefore, manufacturers, such as Optris, adapt the wavelength ranges at which the infrared cameras operate precisely to the respective measuring task. Generally, most material and camera options are categorized as follows, and if necessary, the material must be adapted.

• LT: 8-14µm: Non-metals, non-shiny materials such as plastic, wood, paper, ceramics, brick, carbon, concrete, fabric, organic material, ice, water, paint, plywood, and coated metals.
• G7: 7.9µm: Glass, BK7, thin plastic
• MT: Metals, ceramics, measurement through flames and combustion gases
• 05M, 08M, 1M: Steel, iron, brass, copper, tin, silicon semiconductor

Step 2: Select the correct measurement range and thermal resolution.

The temperature measurement range is all about the lowest and highest temperatures that a camera can accurately capture. In real-world scenarios, this range is shaped by the coldest and hottest temperatures you might encounter in a given scene or application.

When it comes to short-wavelength infrared cameras, they usually handle higher temperature ranges compared to their long-wavelength counterparts. Often, the material of the object being measured plays a crucial role in determining the best spectral range, which then affects the overall measurement range. Commercial infrared cameras can typically measure temperatures from around −40 °C to 2,450 °C, but you won’t find a single device that can handle both extremes. This limitation arises from the camera’s electronics having a restricted dynamic range and the non-linear characteristics of thermal radiation, as outlined by Planck’s law. To get the best performance, measurement ranges are usually split into low, medium, and high-temperature categories, each utilizing specialized low-noise amplifiers.

Finding the right balance between temperature range and spectral range is often best achieved by consulting with application engineers.

Another key specification to consider is temperature resolution, also known as NETD (Noise Equivalent Temperature Difference). NETD tells you the smallest temperature difference the camera can pick up, and it mainly hinges on the noise from the detector. The less noise there is, the better the thermal resolution.
It’s essential to differentiate between temperature resolution and temperature accuracy. Resolution refers to the camera’s ability to detect tiny changes in temperature, while accuracy is about how close the measurement is to the actual temperature. A camera might excel in resolution—showing even the slightest heat variations—yet still have measurement errors that exceed its thermal resolution.

Step 3: Choose the infrared camera’s correct resolution and optics.

Geometric resolution plays a vital role in various applications, and the distance between the infrared camera and the target has a significant impact on it. Important factors to consider include the geometry of the measurement setup, the resolution and physical size of the sensor, and the focal length of the lens. Instead of focusing solely on focal length, manufacturers often highlight the lens’s field of view (FOV) or angle of view. The FOV defines the area that can be observed, while resolution is influenced by pixel size, the number of pixels in the detector, and the distance to the target.

A crucial question in applications is whether we can reliably measure small structures on the target. To achieve the best results, the FOV should encompass the entire target, and the selected lens should optimize the number of pixels covering the measurement area. As the distance increases, both spatial resolution and the number of pixels on the target tend to decrease. Sometimes, getting closer isn’t feasible due to heat, safety issues, or limited access.

Two key terms to keep in mind are instantaneous field of view (IFOV) and measurement field of view (MFOV). IFOV refers to the size of a single pixel on the measurement surface, while MFOV indicates the smallest object size that can be measured reliably and consistently.

From a physics standpoint, diffraction can limit the optical resolution and image quality of infrared systems, even when pixel density is high. Modern bolometer pixel sizes are already approaching infrared wavelengths, which means diffraction effects—like an Airy disk larger than a pixel—can lead to unreliable individual pixel readings, especially in the long-wave range.

For this reason, the smallest object to be measured should always exceed the MFOV rather than just matching the IFOV. Both MFOV and IFOV can be calculated using pixel size, target distance, and the vertical/horizontal FOV of the optics—often with the assistance of an online optical calculator.

Step 4: Selecting the correct frame rate and exposure time.

Infrared cameras rely on three main performance factors: thermal resolution, optical resolution, and temporal resolution. Temporal resolution, which is measured by frame rate, indicates how many images the camera can capture each second. In fast-paced industries like manufacturing, having a high frame rate is crucial for precise monitoring. When temperatures change quickly or when there are moving targets in the camera’s view, a higher temporal resolution becomes necessary.

Some infrared cameras, due to technical limitations or export restrictions, may operate at frame rates below 9 Hz, which isn’t ideal for dynamic situations. The sweet spot for frame rates is typically between 30 Hz and 80 Hz, with some specialized models even reaching up to 1 kHz. However, achieving these higher frame rates often means sacrificing image resolution. In these scenarios, a line-scan mode—where fewer pixels are captured in one dimension (like 764 × 8)—can effectively track fast-moving objects.

Frame rate is closely tied to exposure time (also known as integration time or thermal time constant), which is how long the detector needs to capture a single image. Shorter exposure times help minimize motion blur during high-speed events, leading to clearer images. Interestingly, high-sensitivity cameras usually require shorter exposure times compared to their lower-sensitivity counterparts to produce similar image quality on the same target.

When choosing an infrared camera for high-speed applications, it’s essential to take into account the movement of the object, its heating or cooling rates, and any camera movement itself. This ensures that the selected frame rate and exposure time align with the specific demands of the application.

Step 5: Ensure the infrared camera works in the industrial environment with the right accessories.

In industrial settings, infrared cameras face some tough challenges like extreme heat, dust, vibrations, shocks, smoke, and moisture. One of the biggest hurdles is the maximum operating temperature for the electronics. While many infrared cameras come with built-in processing for edge computing, this usually means they can only handle temperatures below 50 °C. On the other hand, Optris cameras are specifically designed for industrial environments and can function in temperatures as high as 70 °C.

When the installation conditions go beyond these limits, it’s crucial to implement protective measures. Cooling jackets, which can use either water or compressed air, help shield infrared cameras, computers, and network switches from scorching ambient temperatures that can reach up to 315 °C. To complement these solutions, high-temperature-rated signal and connection cables are essential for those extreme environments.

In dusty or smoky situations, air purge collars play a vital role in keeping the optics clean by creating a smooth airflow over the lens. This steady, uniform air curtain stops dust from settling, which helps maintain measurement accuracy and prolongs the camera’s lifespan. For added protection against larger debris, shutter mechanisms can cover the optics when the camera isn’t in use, minimizing the risk of damage from impacts or airborne fragments like broken glass.

For outdoor applications, it’s important to have sturdy, weatherproof housings that often come with built-in heaters, allowing them to operate in temperatures ranging from −40 °C to +50 °C.

Even in less extreme environments, picking the right accessories is key. For instance, adjustable mounting brackets ensure the camera is positioned perfectly and integrates smoothly into the production setup.

Accessories often don’t get the attention they deserve—both in terms of complexity and cost—but they are vital for seamless integration into industrial processes. Thoughtfully chosen housings, mounting systems, high-temperature cables, and other mechanical interfaces guarantee that an infrared camera performs reliably and stays protected, offering a comprehensive, long-term solution for demanding applications.

Step 6: Consider how to integrate the infrared camera into the control loop of the industrial process.

Infrared cameras can be seamlessly integrated into various machines and industrial processes. The latest industrial models often come with the ability to operate autonomously, which means they can be directly incorporated into control loops without needing dedicated PCs or complex software setups. With features like automatic spot finders and compatibility with industrial fieldbus systems—such as EtherNet/IP, ModbusTCP, EtherCAT, IO-Link, or PROFINET—they’re perfect for OEM applications.

Many of these infrared cameras also provide multiple, individually scalable analog outputs, making it easy to send live temperature data to other systems.

However, in most cases, the software is crucial for tapping into the camera’s full capabilities. When assessing a solution, it’s vital to check if the software includes all the necessary functions for your specific application. Key factors to consider are user-friendliness, data export options, and direct system integration. Advanced software should come equipped with comprehensive recording and evaluation tools, real-time analysis, and flexible display options. It should also allow for device-specific tweaks like frame rate adjustments, field of view settings, communication configurations, USB/Ethernet setups, firmware updates, and online configuration file downloads.

If the provided software falls short of your needs, the camera should ideally support a software development kit (SDK) for custom applications. A solid SDK will give you direct access to the thermal imager’s interface on both Linux and Windows platforms and will support various programming languages.

Step 7: Choose a vendor or manufacturer with experienced application support and service.

Choosing the right services and support is crucial—especially when dealing with technology as intricate and adaptable as infrared sensing. Trustworthy infrared camera manufacturers prioritize ensuring their devices provide dependable performance for years to come. But true application support goes beyond just helping customers pick the right model for their needs.

Skilled application engineers can significantly impact the success of a project, offering a range of services from providing updates on order status to demonstrating, testing, and advising on temperature measurement techniques for tricky targets like reflective surfaces. When challenges come up—whether it’s repairs, troubleshooting, or the need for extra training—the quality of aftersales service and the expertise of the technical support team become vital in assessing a supplier.