Fluke 17B+ vs Fluke 15B+

Specs side by side

Specs checked against manufacturer documentation and official Amazon listings. Desk research, not bench testing. How we research.

Key differences

• →Only the 17B+ measures temperature; Fluke includes a Type K probe and specifies −55 °C to 400 °C.
• →Only the 17B+ reads frequency (10 Hz to 100 kHz) and duty cycle; Fluke's manual marks both as 17B+ functions.
• →MIN MAX recording and relative mode are 17B+ only, per Fluke's users manual.
• →The 17B+ has a warning LED that lights at 30V or more, or on an overload; the 15B+ has no such indicator.
• →Everything else matches: same 183 × 91 × 49.5 mm, 455 g case, same safety rating, same 4,000-count display, same current ranges and 1,000 µF capacitance range.
• →Neither is described by Fluke as True RMS, so both are best kept to ordinary sine-wave mains and electronics work.

The functions only the 17B+ has

Put the two side by side and the dials tell the story: the 17B+ has extra positions and buttons, the 15B+ stops at the basics. These are the additions, each confirmed in Fluke's 15B+/17B+/18B+ manual.

Fluke 17B+ vs 15B+ spec by spec

Fluke publishes identical accuracy figures for every function the two meters share. That means the 15B+ is not a lower-grade meter; it is the same instrument with a shorter function list. The table puts the shared specs first and the 17B+ additions last.

The temperature arithmetic: at 200 °C, 2% of the reading is 4 °C, plus 1 °C gives ±5 °C. At −20 °C, 9% of 20 is 1.8 °C, plus 2 °C gives ±3.8 °C. That is plenty for checking an oven element, a heat-sink or a duct, but it is not lab-grade, and the supplied bead probe adds its own tolerance on top.

What MIN MAX catches that a live display misses

A display that updates three times a second can miss a dip that lasts a fraction of a second, and even if it shows, you have to be looking at that moment. MIN MAX on the 17B+ keeps the lowest and highest values it sees while you watch the machine instead of the meter. Fluke allows it on voltage, current and temperature, not on resistance, capacitance, frequency, duty cycle or diode.

That is the classic intermittent fault: a control board that resets when a compressor kicks in, or a car accessory that drops out on crank. The 15B+ can only tell you the supply looks fine now. For more on chasing that kind of problem, see how to find an intermittent electrical fault with a multimeter.

Use cases: where the extras pay off

Appliance and HVAC repair is where the 17B+ earns its keep. A thermocouple on an oven cavity, a dryer exhaust or a supply-air register answers whether the heat source works before you start pulling panels, and the duty-cycle mode reads the PWM command to an EC blower motor. In hobby electronics, frequency and duty cycle cover 555 timers, fan headers and motor drivers.

The 15B+ is the better buy when the job is plainly electrical: checking a breaker's output, a battery, a fuse or a motor's running current. It keeps the same µA range as the 17B+, so flame-rectification checks and standby-current tests still work. Fewer buttons also means fewer chances to leave the meter in an unexpected mode, which some trainers and shared-tool shops value.

Buyer decision flow: 15B+ or 17B+ in four questions

Because the shared functions are identical, the choice reduces to whether any one of the 17B+'s extras would get used. Work down the chart. A single yes is enough, since there is no way to add temperature or a frequency counter to a 15B+ later; four noes mean the extras would sit idle.

The top box matters more than it looks. Fluke makes no True RMS claim for either meter, and their AC current is specified from 40 to 400 Hz and AC volts from 40 to 500 Hz. If a variable-speed drive or electronic dimmer is involved, both will misread its distorted output, and choosing between them misses the point.

Temperature use cases, with the tolerance at each

Fluke splits the 17B+'s temperature accuracy into three bands: ±(9% + 2 °C) from −55 to 0 °C, a flat ±2 °C from 0 to 50 °C, and ±(2% + 1 °C) from 50 to 400 °C, all at 0.1 °C resolution and for the meter alone. Applied to everyday targets, it looks like this. The targets are common reference values, not OhmSavvy measurements; check the appliance maker's own figure before acting on a reading.

Two practical notes. On air-conditioning work, relative mode is allowed on temperature: rest the probe in the return air, press REL, then move it to a supply register and the display shows the drop directly, though each reading still carries its own tolerance. And the 400 °C ceiling belongs to the meter, not necessarily the probe. Fluke's page includes a Type K bead probe without naming its model or its maximum, so don't assume it is good to 400 °C; for a soldering tip or a kiln, use a probe whose own rating you have checked. Our guide on checking a thermocouple with a multimeter covers the furnace-side version of this job, and the 15B+ can do that one too, since it measures the thermocouple's millivolts rather than its temperature.

Frequency and duty cycle use cases

The 17B+ counts from 10 Hz to 100 kHz across five ranges, and the range sets the step: 0.01 Hz on the 50.00 Hz range up to 0.1 kHz on the top one. A US portable generator should hold close to 60 Hz; that lands on the 500.0 Hz range, where the tolerance is 0.1% × 60 + 3 × 0.1 = ±0.36 Hz, fine enough to spot a governor running fast or slow under load. If your generator cuts out when an appliance starts, read the frequency and voltage with the load applied, alongside our guide to a generator that shuts off under load.

Duty cycle carries a catch that Fluke states in small print: the 1% typical accuracy applies at 50 or 60 Hz with a duty between 10% and 90%. A PC or EC-motor fan PWM line usually runs far faster, often around 25 kHz, so a 17B+ reading there is a useful indication (is the controller commanding 30% or 90%?) rather than a specified measurement. The frequency figure itself remains specified at those speeds. The 15B+ has neither mode; on a PWM line its DC volts range shows only the average.

For the budget buyer: value by features

On a tight budget, the useful question is not which meter is better but what the cheaper one costs you in capability. With this pair the answer is precise, because the spec table above splits cleanly: ten shared rows with identical figures and five rows that exist only on the 17B+. Saving money on the 15B+ never means a less accurate volts, amps or ohms reading, a lower safety rating, a weaker fuse or a shorter warranty. It means doing without specific functions, and for each one the question is whether you have a workaround.

Three of the six have reasonable workarounds and three don't. If frequency, duty cycle or catching a brief sag is part of your work, a 15B+ can't do it at all, and the 17B+ is the better value even on a budget. If all you need are volts, amps, ohms, continuity and capacitance, the 15B+ delivers the same measurements and the extra spend would buy dial positions you never turn to. Neither meter is described by Fluke as True RMS, so a budget buyer who works near drives or LED drivers should stretch to a True RMS model instead; the Fluke 117 vs Fluke 15B+ comparison shows what that step adds.

Fluke 17B+ or 15B+: which should you buy?

Comparing either one with a True RMS electrician's meter? Read Fluke 17B+ vs Fluke 117 and Fluke 117 vs Fluke 15B+.

Frequently asked questions