What a Thermal Multimeter Like the Fluke 279 FC Does

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The Fluke 279 FC true RMS thermal multimeter is one example of a thermal multimeter, which combines a true-RMS digital multimeter with a built-in infrared camera. Fluke describes it as both a multimeter and a thermal imager, and it includes a flexible current probe for higher-current readings. This guide explains what the device does, how the two functions are used together, and where the two Fluke pages we opened disagree.

Quick answer

• A thermal multimeter is a digital multimeter with a thermal camera in one body, so you scan for hot or cold spots and then switch to electrical readings.
• The Fluke 279 FC is listed with AC and DC voltage up to 1000 V, resistance to 50 MΩ, and AC current up to 2500 A with the included iFlex probe.
• The two Fluke sources give different infrared resolutions for the camera, so check the manual for the figure that applies to your unit.

How we chose

The keyword names a specific model, so we opened two Fluke pages. One is the Australian product page with specifications. The other is a Fluke learning article that explains what a thermal multimeter is. Both are manufacturer pages. We did not use search snippets, retailer prices or ratings. Where the pages differ, we state the difference in the body.

What a thermal multimeter is

The Fluke learning article describes a thermal multimeter, also called a thermal DMM, as both a digital multimeter and a thermal camera in one. It works as a standard digital multimeter and has a built-in thermal camera, so you do not need to carry two separate tools. The article’s example is the 279 FC, which it describes as having 15 measurements and a thermal imager of 80 × 60 pixels. Its advice is to switch the dial to the camera setting to scan for hot or cold spots, then switch back to take electrical readings.

The article also gives a simple workflow. When you find a hot or cold spot, save the image and note its location. That is useful for a repair report or a follow-up visit, because a thermal image on its own does not say what caused the temperature difference.

What the Fluke 279 FC specification says

The Australian product page gives the following figures. The thermal imager has a 36° × 27° field of view with fixed focus. Its infrared resolution is 102 × 77 pixels. The infrared temperature range is -10 °C to 200 °C (14 °F to 392 °F), with an accuracy of ±7 °C or ±7%, as tested by the manufacturer. The page does not explain the test conditions in the text we read.

The electrical functions are listed as AC and DC voltage up to 1000 V, with CAT III 1000 V and CAT IV 600 V ratings. Resistance goes to 50 MΩ, capacitance to 9,999 µF, and frequency to 100 kHz. The basic DC accuracy is 0.09%. The meter has a rechargeable lithium-ion battery rated for more than 10 hours under normal conditions.

The page also describes the iFlex flexible current probe. The 279 FC includes an 18-inch (45.72 cm) iFlex probe, and with it the page lists AC current up to 2500 A. The probe is a separate sensing accessory, and the page presents it as an add-on that expands the meter’s current range.

Where the two sources disagree

The main conflict is the camera resolution. The product page gives 102 × 77 pixels. The learning article describes an 80 × 60 thermal imager for the 279 FC. We do not choose between them. The product page is the more specific source for this model, but the difference is large enough that you should confirm the figure on the manual or on the label of the unit you buy.

The learning article gives 15 measurements for the 279 FC. The product page does not give a count of measurements in the text we read, so we cannot confirm that figure from the product page.

Scanning in practice

Fluke’s learning article describes scanning as a way to find electrical issues rapidly and from a safe distance. The reason is that a thermal image shows surface temperature, so a hot connection or an overloaded conductor can show as a bright spot before any other symptom. The image is a surface reading, so a warm spot may come from a nearby heat source rather than the fault itself. Check the surrounding conditions before you conclude.

The product page gives an infrared range from -10 °C to 200 °C. Readings outside that range are not in the stated accuracy band, so a thermal scan of very hot equipment is outside the specification. Use a different tool for those measurements.

Step-by-step: a thermal scan and an electrical check

1. Set the meter to the camera function and point it at the equipment at a safe distance.
2. Look for a hot or cold spot that differs from the surrounding surface.
3. Save the image and note the location, as the learning article advises.
4. Switch to the multimeter function and take the electrical reading at the same point, using the leads or the iFlex probe as the job requires.
5. Compare the electrical reading with the thermal image before you draw a conclusion.

This sequence follows the workflow in the learning article. The product page does not give a procedure, and the manual will set the exact steps for your unit.

Safety notes

The product page gives CAT III 1000 V and CAT IV 600 V ratings. Those ratings describe where the meter may be used in an installation, and they depend on the category of the point you measure. Stay within the ratings and follow your site’s safe-work rules for live equipment. A thermal camera does not show voltage, so do not rely on the image to show that a conductor is dead.

What we could not verify

• The camera resolution differs between the two sources, and we could not confirm which figure applies to a given unit.
• The product page does not explain the test conditions behind the ±7 °C or ±7% infrared accuracy.
• The count of 15 measurements comes from the learning article, and the product page did not confirm it in the text we read.
• The sources do not state how the iFlex probe affects the accuracy of the voltage or resistance functions.
• We did not read the operating manual, so battery life and charging details rest on the product page alone.

FAQ

What is the Fluke 279 FC used for?

According to the sources, it is a multimeter with a built-in thermal imager. The camera is used to find hot or cold spots, and the multimeter takes electrical readings at the same point.

Does the 279 FC measure high current?

With the included iFlex probe, the product page lists AC current up to 2500 A. The meter’s own current inputs are not described with the same range in the text we read.

Does a thermal image show voltage?

No. A thermal image shows surface temperature. Use the electrical functions of the meter to measure voltage, and do not treat the camera as a voltage test.

Which camera resolution is correct?

The sources disagree. The product page gives 102 × 77 pixels, and the learning article gives 80 × 60. Confirm the figure in the manual for your unit.

For related reading on this site, see our article on how a current clamp works and our article on handheld digital multimeters.

Bottom line

A thermal multimeter like the 279 FC is worth considering when your work needs both a thermal scan and electrical readings from one tool. Confirm the camera resolution and the test conditions for the infrared accuracy in the manual, and stay within the stated temperature range and safety ratings.

Sources

• Fluke, 279 FC product page, Australia English: https://www.fluke.com/en-au/product/electrical-testing/digital-multimeters/fluke-279-fc (opened 2026-10-30)
• Fluke, What is a thermal multimeter, learning article, Canada English: https://www.fluke.com/en-ca/learn/blog/digital-multimeters/what-is-a-thermal-multimeter (opened 2026-10-30)