COMPARISON · MULTIMETERS
Fluke 27 II vs Fluke 28 II: Differences Explained
The Fluke 27 II and 28 II share one physical meter: the same IP67 case, 3 m drop rating, MSHA approval, −15 to +55 °C operating range, three AA cells for about 800 hours, 698.5 g holstered weight, CAT IV 600V / CAT III 1000V rating and limited lifetime warranty. The difference is inside. The 28 II measures AC as True RMS and adds a low-pass filter for motor drives, a −200 to +1090 °C temperature input with a probe in the box, 250 µs peak capture, a 20,000-count high-resolution mode and tighter DC volts. The 27 II is average responding, so it is only accurate on clean sine waves.
By the OhmSavvy Research Team ·
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Fluke 28 II
4.6★★★★★An IP67, MSHA-approved True RMS meter with 87V-class volts accuracy, a low-pass filter and a 3 m drop rating.
Fluke 27 II
4.4★★★★☆The 28 II's IP67, 3 m-drop body with average-responding AC, for harsh sites where the loads are plain sine waves.
Specs side by side
| Fluke 28 II | Fluke 27 II | |
|---|---|---|
| Rating | 4.6★★★★★ | 4.4★★★★☆ |
| Accuracy | True RMS, 0.05% + 1 DC V | Average responding, ±(0.1% + 1) DC V |
| Safety rating | CAT IV 600V / CAT III 1000V | CAT IV 600V / CAT III 1000V |
| Auto-ranging | Yes (manual override) | Yes (manual RANGE) |
| Best for | Wet, dusty and mining sites | Wet, dusty or cold sites with sine-wave loads |
| AC measurement | True RMS | Average responding ("AVG") |
| DC volts accuracy | 0.05% + 1 | 0.1% + 1 |
| AC volts accuracy | 0.7% + 4 | 0.5% + 3 |
| AC bandwidth | 15 Hz to 20 kHz | 40 Hz to 30 kHz |
| DC amps / AC amps | 0.2% + 4 / 1.0% + 2 | 0.2% + 4 / 1.5% + 2 |
| Display | 6000 counts; 20,000-count hi-res mode | 6000 counts |
| Low-pass (VFD) filter | Yes | Not listed |
| Peak capture | 250 µs | Not listed |
| Temperature | −200 to +1090 °C, 80BK-A probe included | Not listed |
| Backlit keypad | Yes, plus two-level backlight | Backlight listed; keypad not stated |
| IP / drop / MSHA | IP67 / 3 m / approved | IP67 / 3 m / approved |
| Battery | 3 × AA, 800 h | 3 × AA, 800 h |
| Size / weight, holstered | 6.35 × 10.0 × 19.81 cm, 698.5 g | 6.35 × 10.0 × 19.81 cm, 698.5 g |
| Warranty | Limited lifetime | Limited lifetime |
Specs checked against manufacturer documentation and official Amazon listings. Desk research, not bench testing. How we research.
Key differences
- →AC conversion: the 28 II is True RMS on AC volts and amps. The 27 II is sold as the "AVG" model, an average-responding meter calibrated for sine waves.
- →Drive work: only the 28 II lists a low-pass filter for variable speed drives and 250 µs peak capture.
- →Temperature: the 28 II reads −200 to +1090 °C and ships with the 80BK-A probe. Fluke lists no temperature function for the 27 II.
- →Resolution and DC accuracy: the 28 II adds a 20,000-count mode and halves the DC volts percentage, 0.05% against 0.1%.
- →On a clean sine, the 27 II's published AC volts line is tighter, 0.5% + 3 against 0.7% + 4, and its bandwidth runs higher, to 30 kHz.
- →Identical: case, IP67, 3 m drop, MSHA approval, cold rating, battery, weight, current span to 10 A, resistance, capacitance and frequency ranges, CAT ratings and warranty.
One body, two measuring engines
Fluke built these two as a pair. Its product pages print the same holstered dimensions, the same 698.5 g, the same IP67 seal and the same 10 ft drop test for both, and the 28 II page links its sibling as the "AVG Multimeter" next to its own "True-rms" label. So the buying decision isn't about toughness at all. It comes down to the kind of AC you measure and whether you want the 28 II's extra functions.
Shared armor
IP67, 3 m drop, MSHA approval and the same cold rating on both.
28 II: True RMS
Correct AC readings on distorted waveforms from drives and electronics.
28 II: drive tools
Low-pass filter and 250 µs peak capture for VFD troubleshooting.
28 II: temperature
Type-K input to +1090 °C, with the 80BK-A probe in the box.
27 II: sine-wave AC
Average responding, so readings drift once the waveform distorts.
27 II: wider AC band
40 Hz to 30 kHz, against 15 Hz to 20 kHz on the 28 II.
We haven't hands-on tested either model. The scores on this page (4.6 for the 28 II, 4.4 for the 27 II) come from desk research, and every number below is taken from Fluke's two product pages or the official Amazon listings. When Fluke leaves a line blank, so do we.
Fluke 27 II vs 28 II spec by spec
| Spec | Fluke 28 II | Fluke 27 II | Difference |
|---|---|---|---|
| AC conversion | True RMS | Average responding | 28 II |
| DC volts | 0.1 mV to 1000 V, 0.05% + 1 | 0.1 mV to 1000 V, 0.1% + 1 | 28 II |
| AC volts | 0.1 mV to 1000 V, 0.7% + 4 | 0.1 mV to 1000 V, 0.5% + 3 | 27 II on sine only |
| AC bandwidth | 15 Hz to 20 kHz | 40 Hz to 30 kHz | Depends on job |
| DC amps | 0.1 µA to 10 A, 0.2% + 4 | 0.1 µA to 10 A, 0.2% + 4 | Same |
| AC amps | 1.0% + 2 | 1.5% + 2 | 28 II |
| Overload | 20 A for 30 s | 20 A for 30 s | Same |
| Resistance range | 0.1 Ω to 50 MΩ | 0.1 Ω to 50 MΩ | Same |
| Capacitance range | 1 nF to 9999 µF | 1 nF to 9999 µF | Same |
| Frequency range | 0.5 Hz to 199.99 kHz | 0.5 Hz to 199.99 kHz | Same |
| Counts | 6000; 20,000 hi-res | 6000 | 28 II |
| Low-pass filter | Yes | Not listed | 28 II |
| Peak capture | 250 µs | Not listed | 28 II |
| Temperature | −200 to +1090 °C | Not listed | 28 II |
| Min/Max/Avg, hold, relative | Yes | Yes | Same |
| IP rating / drop | IP67 / 3 m | IP67 / 3 m | Same |
| MSHA | Approved | Approved | Same |
| Operating range | −15 to +55 °C; −40 °C for 20 min | −15 to +55 °C; −40 °C for 20 min | Same |
| Safety rating | CAT IV 600V / CAT III 1000V | CAT IV 600V / CAT III 1000V | Same |
| Battery | 3 × AA, 800 h | 3 × AA, 800 h | Same |
| In the box | TL75 leads, AC175 clips, 80BK-A | Holster, test leads, clips | 28 II adds probe |
The arithmetic behind those bars assumes the ranges a 6000-count meter normally uses: a 60.00 V range for 24 V (one count is 0.01 V) and a 600.0 V range for 120 V (one count is 0.1 V). For 24 V DC, the 28 II allows 0.05% of 24 (0.012 V) plus one count, so about ±0.022 V; the 27 II allows 0.1% (0.024 V) plus one count, about ±0.034 V. For a 120 V sine, the 27 II allows 0.5% (0.6 V) plus three counts (0.3 V), about ±0.9 V, while the 28 II allows 0.7% (0.84 V) plus four counts, about ±1.24 V. Fluke's pages don't print the range table or the frequency band each accuracy line applies to, so treat these as illustrative.
Bars use a logarithmic scale: each step is ten times the last.
Why average responding goes wrong on distorted AC
An average-responding meter rectifies the AC, takes the average, and multiplies by about 1.111, which is the ratio between RMS and average for a pure sine. That shortcut is exact on a sine and only on a sine. Feed it a different shape and the multiplier is wrong for that shape. A True RMS meter computes the heating-equivalent value directly, so it doesn't care what the waveform looks like, within its crest-factor and bandwidth limits.
The numbers come from simple ratios. A square wave of 100 V peak has an RMS of 100 V and an average of 100 V, so the meter shows 100 × 1.111 = 111 V. A pulse train that is on for a quarter of the time, scaled to 100 V RMS, has an average one-half of its RMS (the square root of 0.25), so the meter shows 0.5 × 1.111 × 100, about 56 V. The narrow-pulse case is the one that bites in the field: the current drawn by rectifier front ends in drives, computers and LED drivers arrives in short, tall peaks, so an average-responding meter tends to read that current low.
| Circuit you are measuring | Typical AC shape | 27 II | 28 II |
|---|---|---|---|
| Utility outlet or panel voltage | Close to sine | Fine | Fine |
| Resistive heater current | Follows the voltage | Fine | Fine |
| VFD output to a motor | Switched pulses | Unreliable | Use low-pass filter |
| Current into a drive, PC or LED driver | Peaky pulses | Likely reads low | Correct within spec |
| UPS or inverter output | Varies by design | Check with True RMS | Correct within spec |
| DC supplies, batteries, sensors | DC | Fine | Fine |
For a longer explainer and cheaper True RMS options, see our budget True RMS multimeters guide.
The 28 II's extra tools, in practice
Low-pass filter. On the output side of a variable speed drive, the voltage is a train of fast switched pulses. The filter strips the high-frequency switching content so the 28 II reads something close to the voltage the motor actually responds to. The 27 II lists no filter, and its higher 30 kHz bandwidth would let more of that switching noise into the reading.
Peak capture. At 250 µs, the 28 II can hold short spikes and dips that a normal Min/Max would average away, which helps when a contactor or a motor start drags a supply down for a moment.
Temperature. With the included 80BK-A bead probe, the 28 II covers bearing, enclosure and pipe checks without a second tool. The meter's range is −200 to +1090 °C; the probe you plug in sets the practical limit.
High resolution. The 20,000-count mode adds a digit for slow-changing readings such as sensor voltages, and the backlit keypad helps in a dark vault or mine heading.
The only question that matters
Fluke 27 II vs 28 II: which should you buy?
| Your work | Buy | Reason |
|---|---|---|
| Mine electrician with conveyor drives | Fluke 28 II | MSHA on both, but drives need True RMS and the filter |
| Mine or quarry mechanic, mostly DC and continuity | Fluke 27 II | Same sealed body; averaging doesn't affect DC |
| Water or wastewater pump stations with VFDs | Fluke 28 II | Filter and True RMS on drive outputs |
| Outdoor lighting and utility-fed heaters | Either | Close-to-sine AC; the 27 II's AC line is tighter |
| HVAC or refrigeration in wet plant rooms | Fluke 28 II | Temperature input and probe included |
| Agricultural or fleet equipment, 12/24 V DC | Fluke 27 II | DC work, IP67 body, lower model in the pair |
If the sealed case matters but you also want the most complete published spec, compare the 28 II with its closest rival in Fluke 28 II vs Fluke 87V MAX, or weigh the rugged average-responding model against an industrial True RMS meter in Fluke 27 II vs Fluke 87V MAX. For dry plant floors, our Fluke 28 II vs Fluke 87V page covers the meter we have tested ourselves.
Safety: a wrong AC reading is a safety problem, not only an accuracy problem
Choose the Fluke 28 II if…
- ✓You measure anything fed by a drive, inverter, LED driver or switch-mode supply, where AC is not a clean sine
- ✓You want temperature on the same meter, with the 80BK-A type-K probe included
- ✓You want a high-resolution mode, peak capture or tighter DC volts for calibration-style checks
Choose the Fluke 27 II if…
- ✓Your AC work is utility-fed, linear loads: resistance heaters, incandescent lighting, induction motors run straight off line power
- ✓Most of your readings are DC, resistance and continuity, where averaging doesn't apply
- ✓You want the sealed, drop-rated, MSHA-approved body and have no use for temperature or a drive filter
The bottom line
The Fluke 27 II and 28 II are the same rugged meter outside: IP67, a 3 m drop rating, MSHA approval, 800 hours on three AAs and a lifetime warranty. Buy the 28 II if any of your AC involves drives, inverters or electronic loads, or if you want temperature, peak capture and a hi-res mode. Buy the 27 II only if your AC is clean line power and most of your readings are DC, resistance and continuity.
Frequently asked questions
Is the Fluke 27 II True RMS?+
No. Fluke's Amazon listing calls it the 27II AVG multimeter, and Fluke's own 28 II page labels the 27 II as the AVG model next to the True RMS 28 II. Average responding is accurate on clean sine waves but drifts on distorted waveforms such as drive outputs or the current drawn by electronic loads.
Do the Fluke 27 II and 28 II have the same case?+
Yes. Fluke lists both at 6.35 × 10.0 × 19.81 cm and 698.5 g with the holster, both IP67 and both tested for a 3 m (10 ft) drop. Both are MSHA approved, rated −15 to +55 °C with 20-minute excursions to −40 °C, and run about 800 hours on three AA cells.
Can the Fluke 27 II measure temperature?+
Fluke doesn't list a temperature function for the 27 II, and none of its included accessories is a probe. The 28 II reads −200 to +1090 °C and ships with the 80BK-A type-K bead probe, so if you need temperature in a sealed meter, the 28 II is the one to buy.
Can I use the Fluke 27 II on a VFD?+
Not for reliable output readings. A drive's output is a switched pulse train, and an average-responding meter without a low-pass filter can read it well off. The 28 II is True RMS and lists a low-pass filter for variable speed drives. On the drive's line-side voltage, a clean sine, the 27 II is fine.
Why is the 27 II's AC volts accuracy better than the 28 II's?+
On paper it is: 0.5% + 3 against 0.7% + 4. That figure only holds for a sine wave, because an average-responding meter is calibrated assuming that shape. On distorted AC its real error can be far larger than any published line, while the 28 II's True RMS reading stays within its spec.
Are both the Fluke 27 II and 28 II MSHA approved?+
Yes, Fluke lists MSHA approval on both product pages. Neither is intrinsically safe for explosive atmospheres; Fluke sells a separate 28 II EX for classified areas. Check with your mine's safety department which approvals your site's electrical program requires before you buy.
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