Infrared Thermometers

Flir TG54 24:1 spot IR thermometer
Flir TG54 24:1 spot IR thermometer
Published On
Jan 15, 2020

To use a baseball analogy, the infrared (IR) thermometer is a true “utility player” for electricians, believes Richard Wexler, director of instrument marketing at Flir. IR thermometers are useful for identifying abnormal conditions indicated by changes in temperature.

“Also called spot thermometers, IR guns and spot pyrometers IR thermometers can make troubleshooting faster, safer and simpler by helping identify issues that have not yet resulted in equipment failure so that they can be repaired at a scheduled time and at a lower cost than a total replacement.” Wexler said.

Loose connections are a good example.

“A loose connection may have increased resistance, resulting in hotter temperatures than wires nearby that are in better conditions,” Wexler said. “Overloaded circuit breakers warm up noticeably and that temperature disparity can be detected by an infrared thermometer.

“Scanning electrical equipment with an IR thermometer provides a quick way to zoom in on trouble spots. And because they are noncontact, an electrician can inspect equipment at a safe distance, which is particularly useful around moving components, such as motors and mechanical equipment.”

Compared to earlier models, today’s IR thermometers have advanced in terms of better distance-to-spot ratios, so an electrician can stand at a safer distance from equipment without broadening the size of the spot measured, Wexler said. Newer models permit users to read a 1-inch spot accurately from 24–30 inches away, compared to 12–20 inches in older instruments.

“From a usability perspective, newer, colorful matrix displays with high-contrast white on black digits are easier to read in glare or dim lighting conditions than traditional green LCDs limited to seven-segment digits,” he said. “Newer screens offer users clearer menu navigation to settings and functions.”

In terms of durability, Wexler suggests looking for IR thermometers that are tough enough to survive drops off a ladder at heights from 6 to 9 feet. While some newer heavy-duty models are bulky and tougher to store among other tools, newer designs combine a compact shape with rugged performance.

Unlike thermal imaging cameras, infrared thermometers generally are easier to deploy out of the box, but learning is required for effective use, Wexler said.

A big source of confusion when using IR thermometers is emissivity. Different surface materials emit radiation with varying degrees of effectiveness, and an infrared thermometer needs to compensate for that. Factors that affect emissivity include whether the surface is reflective, metallic or painted. For example, a flat black surface has good emissivity.

“Some electricians use the old trick of putting black electrical tape on a shiny surface in order to provide a flat, nonreflective surface to measure temperatures,” Wexler said. “Higher level infrared thermometers today offer adjustable emissivity to help a user calibrate the tool to a given surface. It is time well-spent getting acquainted with a tool’s emissivity adjustments.”

If an electrician is using a device with nonadjustable or fixed emissivity, the measurement might not always be accurate. These should be used more for comparative measurements among related components than for absolute temperature readings.

Wexler said a notable application for IR thermometers relates to newer, more sophisticated energy-storage systems. The Tesla PowerWall for residential applications and the Tesla PowerPack for utility and business energy storage provide high-
capacity battery storage for energy from solar, wind or conventional sources during off-peak times.

Flir, known for thermal imagers, offers a wide selection of IR thermometers plus a hybrid spot thermal camera. This newer type of thermometer provides a visual display of temperature differences like a thermal imaging camera, but with a narrower field of view comparable to the measurement spot of an IR thermometer.

“These hybrids have generated a lot of excitement by equipping electrical contractors with the laser pointers of an IR thermometer with the added convenience of visual troubleshooting,” Wexler said.

Klein dual-laser IR thermometer
Klein dual-laser IR thermometer

Klein Tools Product Manager Sabrina Kalsi said the demand for IR thermometers is growing for electrical installation and troubleshooting, with equipment maintenance, indoor air quality and HVAC/R areas where an IR temperature meter can provide quick, easy and accurate temperature readings.

“IR thermometers provide a safe, noninvasive method for detection of potential electrical system failures by detecting hot spots in electrical panels or systems, and, while performing maintenance on motors and equipment, they can detect the first sign of problems,” Kalsi said. “The advantage of the IR thermometer is the user does not need to touch the surface being measured. Live circuits, fragile computer circuitry, moving belts/gears, out-of-reach ducts or high heat are not a problem for an IR thermometer.”

Kalsi said IR thermometers today are more affordable, durable and convenient than previous models.

“Some professional products offer a dual laser and the two points help to accurately define the temperature measurement area to the customer. We offer products that combine two core tools that make an IR thermometer also a pocket tester,” she said.

Other new products offer features like a Type-K thermocouple measurements, or a relative humidity measurement for more accurate indoor air quality measurements.

While IR thermometers are considered simple, easy-to-use devices, Kalsi said users need to understand several things to ensure the best accuracy.

“A common misunderstanding is that IR thermometers measure the temperature of the surface only and not the internal temperature,” she said.

Users should also consider the distance-to-spot ratio.

“The distance-to-spot ratio defines the size of the area being measured relative to the distance between the measurement location and the IR sensor. The area being measured becomes larger as the distance from the IR sensor increases,” Kalsi said.

She also explained that because IR thermometers measure surface temperature and emissivity and different types of surfaces emit thermal energy at different efficiencies, different emissivity coefficients must be considered in order to make accurate measurements when reading the temperature of different materials.

“Professional IR thermometer models allow the user to set the emissivity for the type of material being measured. Charts are usually provided for guidance to estimate the emissivity,” Kalsi said.

Finally, she said, “IR thermometers are not good at measuring liquids or gas temperatures.”

Klein offers a range of IR thermometer models based on application requirements that include a single-laser, fixed emissivity IR thermometer and noncontact voltage tester; combination noncontact voltage tester with a single target laser, a temperature range of –22°F to 482°F (–30°C to 250°C), with fixed emissivity; and professional IR target guns with dual target lasers and adjustable emissivity and broader temperature range capabilities.

Milwaukee 12:1 Infrared Temp-Gun
Milwaukee 12:1 Infrared Temp-Gun

Milwaukee Tool Senior Product Manager Troy Marks said the most significant change has been the improvements in size. Infrared imagers continue to get smaller and more compact. In addition, the micronization of the sensors has allowed manufacturers to boost the capabilities of the tools without having to sacrifice on that size.

“Electrical contractors most often use IR thermometers for predictive maintenance and troubleshooting,” Marks said. “Common applications include inspecting electrical connections, checking for unbalance in circuits and identifying damage to cabling or cable insulation. This is done to detect early warnings of failure, potential safety hazards and where energy loss is occurring.”

He added the most common equipment that is inspected in these applications include switch gears, breakers, bus ducts, fuse clips, transformers and capacitors.

Marks notes in shift in the IR thermometer and thermal imager markets.

“An infrared thermometer is a valuable tool anywhere that heat or temperature variations can signify a problem,” Marks said. “But thermal imagers have long been considered the step-up from IR thermometers due to their imaging capabilities.”

“High distance-to-spot ratio infrared temperature guns are starting to overlap in price with low-cost thermal imaging products, and users who need high distance-to-spot ratios are ideal prospects for low-cost thermal imagers because they benefit from the visual thermal image created while still providing accurate measurements at long distances. The availability of more affordable thermal imagers has made these tools more accessible to all electricians, so it’s no longer a specialty application. We’ve developed solutions that don’t sacrifice pixel resolution for cost. These solutions are easier to use, more compact and have similar features as higher-end units.

“With more affordable high-quality thermal imagers like these, service electricians in particular now have a tool available that allows them to be a key player in determining issues,” Marks said.

Milwaukee offers a range of temperature guns for professional, residential, commercial and industrial applications with varied temperature range and distance-to-spot ratios from 10:1 to 30:1.

IR thermometers are becoming more sophisticated with a growing number of features and modes, and they’re becoming increasingly popular.

Citing forecasts from Grand View Research, San Francisco, Wexler said infrared thermometers represent the fastest growing segment among thermometers overall. Persistence Market Research, New York, places the North American market for infrared thermometers to be valued at $200.4 million and nearly doubling to $400 million by 2026.

“One factor driving more demand is that more and more electrical contractors are getting familiar with IR thermometers.  Along with a mainstay of HVAC/R and mechanical contractor tool buckets, more and more electricians see the value of faster and safer heat detection,” Wexler said. 

About the Author

Jeff Griffin

Freelance Writer

Jeff Griffin, a construction and tools writer from Oklahoma City, can be reached at

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