Overview: This article covers temperature measurement methods, focusing on infrared thermometers and thermal imaging cameras, highlighting their key components, principles, applications, and devices from Fluke.

Temperature measurement is essential for safety, quality control, and efficiency across many fields. It helps prevent equipment failures, ensures product consistency, supports accurate medical diagnostics, and optimizes energy use.

What Are the Various Technologies Used in Temperature Measurement?

Temperature measurement technologies can be categorized in several ways depending on their operating principles and applications. The two main categories include

  • Non-Contact Methods: It measures temperature remotely by detecting emitted radiation (e.g., infrared thermometers, thermal imaging cameras, optical pyrometers).

This article briefly summarizes about two main types of non-contact temperature measurement devices, which include infrared thermometers and thermal imaging cameras.

Non-Contact Methods

Both non-contact methods (infrared thermometers and thermal imaging cameras) operate on the same fundamental principle: they passively detect and measure infrared radiation emitted by objects.

Any object with a temperature above absolute zero (-273.15°C or 0 Kelvin) emits infrared radiation due to the thermal motion of its atoms and molecules. Infrared occupies the region of the electromagnetic spectrum between 8 and 15 μm, as shown in Fig. 1. The majority of energy in this range is emitted as heat, making it detectable both during the day and at night.

Diagrammatic illustration of the electromagnetic spectrum.

Fig. 1 Diagrammatic Illustration of the Electromagnetic Spectrum. Source: MDPI

Emissivity(ε) is a property of a material of how effectively a material emits infrared radiation compared to an ideal \"black body\" at the same temperature.

  • 0% Emissivity (ε = 0): The object is a perfect thermal mirror, reflecting all incident infrared radiation and emitting none of its own.

  • 100% Emissivity (ε = 1): The object is a perfect black body, absorbing all incident energy and radiating the maximum possible amount of thermal energy.

Why Emissivity Matters in Infrared Measurements?

Most real objects have emissivity values between 0 and 1, which depend on the material and its surface properties. Accurate temperature readings with infrared devices require knowledge of the object\'s emissivity. If emissivity is set incorrectly, the measured temperature can be significantly wrong.

Infrared Thermometer

Also called a thermal radiation thermometer is a non-contact measuring device that detects infrared radiation emitted by an object and converts it into an electrical signal displayed as temperature. It is useful for measuring surfaces that are moving, hard to reach, hazardous, or too hot for traditional sensors. Infrared thermometers are widely used in cooking, industrial, electronics, medical, and HVAC applications.

Infrared thermometers can be inaccurate due to emissivity issues. They detect not only emitted energy from the target but also reflected and transmitted energy, leading to errors. Accuracy decreases with distance because the atmosphere doesn't perfectly transmit thermal energy. Additionally, they only measure temperature at a single point on the surface.

Thermal Imaging Camera

Infrared thermal imaging is a technology that detects heat without touching or damaging the object being measured. Thermal cameras work differently from regular cameras; they "see" by detecting heat, not visible light. Instead of seeing reflected light, it mostly sees the heat that objects give off. This is why thermal cameras are useful for seeing people, animals, or other warm things, even in the dark or through smoke.

Key Components and Working Principle

Thermal imaging can capture thousands of temperature measurements simultaneously. It uses an array of infrared detectors and special lenses to capture the heat energy given off by an object. The sensor then sends this information to electronic components for processing, which produces a thermal image. The various steps involved in thermal imaging, as shown in Fig. 2, can be detailed in a sequential manner:

Diagrammatic illustration of the working principle of a thermal imaging camera.

Fig. 2 Diagrammatic Illustration of the Working Principle of a Thermal Imaging Camera. Source: MDPI

  • Everything emits infrared (heat) radiation. This is the starting point, where the infrared energy comes from the scene or object being observed.

  • The emitted infrared radiation travels through the atmosphere. During this journey, some of the energy may be absorbed or scattered by particles in the air.

  • Special lenses and mirrors in the thermal imaging device collect and focus the incoming infrared radiation.

  • The focused infrared energy hits the focal plane detectors (sensors), which convert the infrared radiation into electrical signals.

  • Some unwanted signals (noise) from the system may mix with the real data at this stage.

  • The electrical signals, including both the real signal and noise, are processed digitally to improve image quality and remove as much noise as possible.

  • Finally, the processed data is used to create and display a thermal image, which shows the heat distribution of the scene and displays temperature patterns using color gradients

This diagnostic technique is safe for humans, offers excellent concealment, and can operate in all weather conditions. As a result, it is widely used in fields such as electrical power, medicine, construction, aviation, transportation, industry, and more. However, infrared thermal imaging typically produces images with low contrast and limited detail, so several processing steps are needed to improve image quality.

Infrared thermal images often suffer from low contrast, poor resolution, fuzzy edges, and low accuracy due to environmental factors, sensor limitations, and noise. To address this, processing algorithms are used to correct non-uniformity, reduce noise, and enhance edges.

An Infrared Thermometer to Consider

FLUKE-62 MAX by Fluke Corporation

The Fluke 62 MAX+, as shown in Fig. 3, offers industrial-grade temperature measurement with ±1.0°C accuracy across -30°C to 650°C. It's a 12:1 distance-to-spot ratio with dual lasers that ensures precise targeting, while adjustable emissivity settings compensate for material variations. Durable IP54 construction and 3-meter drop resistance make it ideal for HVAC, electrical, and automotive applications requiring reliable non-contact readings.

64 MAX, 62 MAX+, and 62 MAX Infrared Thermometers.  

Fig.3: 64 MAX, 62 MAX+, and 62 MAX Infrared Thermometers. Source: Fluke

An Infrared Thermal Imager to Consider

Fluke Ti300+ Thermal Imager

The Fluke Ti300+ Thermal Imager, as shown in Fig. 4, delivers professional-grade thermal inspection with 320×240 pixel resolution, capturing temperatures from -20°C to 650°C with ±2°C accuracy.

Fluke Ti300+ Thermal Imagers.

Fig. 4: Fluke Ti300+ Thermal Imagers. Source: Fluke

Its standout features include LaserSharp™ Auto Focus for precise targeting, as shown in Fig. 5, IR-Fusion™ technology that blends visible and infrared images for enhanced detail, and robust wireless connectivity through the Fluke Connect™ app for seamless data management.

Fluke's LaserSharp® Auto Focus uses a built-in laser to precisely measure and focus on your selected target, even in difficult inspection sites.

Fig. 5: Fluke's LaserSharp® Auto Focus Uses a Built-in Laser to Precisely Measure and Focus on Your Selected Target, Even in Difficult Inspection Sites. Source: Fluke

Built for industrial environments, it features a rugged IP54-rated design that withstands 2-meter drops, intuitive touchscreen operation, and multiple data annotation options, making it ideal for preventive maintenance and electrical troubleshooting applications.

Summarizing the Key Points

  • Infrared thermometers and thermal cameras detect heat remotely by measuring emitted infrared radiation, enabling precise non-contact temperature monitoring in various conditions.

  • Emissivity significantly impacts infrared temperature readings; knowing and setting the correct emissivity value ensures measurement accuracy for different materials.

  • Thermal imaging captures thousands of temperature points simultaneously, producing heat maps that visualize heat distribution, important for maintenance, safety, and diagnostics.

  • Devices like Fluke Ti300+ and Fluke 62 MAX+ offer rugged, accurate, > and reliable temperature measurement tools suitable for industrial > environments, ensuring safety and efficiency.

Reference

Nguyen, T. X. B., Rosser, K., & Chahl, J. (2021). A review of modern thermal imaging sensor technology and applications for autonomous aerial navigation. Journal of Imaging, 7(10), 217. https://doi.org/10.3390/jimaging7100217

Hou, F., Zhang, Y., Zhou, Y., Zhang, M., Lv, B., & Wu, J. (2022). Review on infrared imaging technology. Sustainability, 14(18), 11161. https://doi.org/10.3390/su141811161

Dong, Y., Sloan, G., & Chappuies, J. (2024b). Open-source time-lapse thermal imaging camera for canopy temperature monitoring. Smart Agricultural Technology, 7, 100430. https://doi.org/10.1016/j.atech.2024.100430

Oemsecrets. (n.d.-a). Fluke 62 MAX+ - Compare distributor prices & inventory | oemsecrets.com. oemsecrets.com. https://www.oemsecrets.com/compare/Fluke%2062%20MAX%2B%20

Oemsecrets. (n.d.-b). Fluke TI300+ - Compare distributor prices & inventory | oemsecrets.com. oemsecrets.com. https://www.oemsecrets.com/compare/Fluke%20Ti300%2B