COMPARISON · MULTIMETERS
Fluke 1577 vs Fluke 87V: Insulation Tester or Industrial Multimeter?
If you have to prove insulation is sound before a motor, cable or panel goes back into service, you need an insulation tester like the Fluke 1577; the 87V can't do that job at any price. If your work is finding faults on live equipment, the Fluke 87V is the better tool and is enough on its own. The 1577 applies 500 V or 1000 V DC and reads insulation up to 600 MΩ, but as a meter it stops at 400 mA and drops capacitance, frequency and temperature. The 87V, which we have bought and tested, reads to 10 A with ±(0.05% + 1) DC volts, a low-pass filter and peak capture. This Fluke 1577 vs 87V comparison is really a question about your workload.
By the OhmSavvy Research Team ·
Disclosure: OhmSavvy earns a commission from qualifying Amazon purchases made through these links, at no extra cost to you. How we're funded.
Fluke 1577
4.5★★★★★A True RMS multimeter with a 500 V / 1000 V insulation tester built in, for motor, cable and switchgear checks.
Fluke 87V
4.8★★★★★The step-up pick for anyone who needs CAT IV protection and high-resolution readings daily.
Specs side by side
| Fluke 1577 | Fluke 87V | |
|---|---|---|
| Rating | 4.5★★★★★ | 4.8★★★★★ |
| Accuracy | True RMS, ±(0.2% + 2) DC V | True RMS |
| Safety rating | CAT IV 600V / CAT III 1000V | CAT III 1000V / CAT IV 600V |
| Auto-ranging | Yes (manual RANGE) | Yes |
| Best for | Motor, cable and switchgear insulation checks | Industrial technicians, daily professional use |
| Insulation test | 500 V and 1000 V; 0.1 to 600 MΩ | No |
| Insulation accuracy | ±(2.0% + 5) | Not applicable |
| PI / DAR, wireless | Not listed / none | No / none |
| DC volts accuracy | ±(0.2% + 2) | ±(0.05% + 1) |
| AC volts accuracy | ±(2% + 3) at 50–60 Hz | ±(0.7% + 2) |
| Low-pass filter | No | Yes |
| Current | 60 mA and 400 mA only | To 10 A (20 A for 30 s); 0.01 µA DC resolution |
| Resistance | To 50 MΩ, ±(1.2% + 2) to 6 MΩ | To 50 MΩ, ±(0.2% + 1) |
| Capacitance / frequency / temperature | No / no / no | 9,999 µF / 200 kHz / -200 to 1090 °C |
| Display | 6,000 counts (data sheet) | 6,000 counts; 19,999 hi-res |
| Enclosure / drop | IP40 (non-operating) / not stated | IP30 / 3 m or 1 m (Fluke differs) |
| Battery | 4 × AA; 1000 h, ≥1000 IR tests | 9V, ~400 h |
| Weight | 550 g or 624 g (Fluke differs) | 355 g; 624 g with holster |
| Warranty | 3 years | Lifetime |
Specs checked against manufacturer documentation and official Amazon listings. Fluke 87V is hands-on tested by OhmSavvy; the Fluke 1577 assessment is desk research. How we research.
Key differences
- →Insulation: the 1577 drives 500 V or 1000 V DC through the insulation and reads up to 600 MΩ. The 87V's ohms range uses a low test voltage and stops at 50 MΩ, so it can't reveal insulation that only fails under stress.
- →Current: the 87V reads to 10 A in series and resolves 0.01 µA DC. The 1577 has only 60 mA and 400 mA ranges.
- →Meter depth: the 87V adds capacitance, frequency, temperature, a low-pass filter for drive outputs, a 19,999-count mode and 250 µs peak capture. Fluke lists none of these on the 1577.
- →Accuracy: on DC volts the 87V is ±(0.05% + 1) against ±(0.2% + 2); on AC volts ±(0.7% + 2) against ±(2% + 3).
- →Same: both are True RMS and rated CAT IV 600V / CAT III 1000V, and neither has wireless or logging.
- →Ownership: the 87V has a lifetime warranty and is our Hands-on Tested pick; the 1577 has three years and is rated from Fluke's specs.
Do you need megohm testing at all?
Plenty of skilled electricians go years without running an insulation test, and plenty of maintenance technicians run several a week. The difference is not seniority; it's whether your job includes deciding that de-energized equipment is safe to energize. That decision is what an insulation tester exists for. Live troubleshooting, by contrast, is almost entirely multimeter work, and there the 87V is the stronger tool.
Typical "yes" jobs: a motor that sat in a flooded pit, a feeder pulled through a new conduit run, a pump motor going back in after bearing work, a cable that keeps tripping a ground-fault relay. Typical "no" jobs: a drive throwing faults, a contactor that won't pull in, a sensor reading wrong, a circuit with voltage drop. If most of your list is the second kind, the 87V alone covers you.
Why the 87V's ohms range can't stand in for a megohmmeter
It's tempting to switch the 87V to ohms, put one lead on a winding and the other on the frame, see "OL" and call it good. That proves there's no dead short. It doesn't prove the insulation will survive 480 V and the switching spikes that ride on it, because a low-voltage ohms test barely stresses the insulation at all. Cracked varnish, tracking across a dirty terminal block or moisture in a cable can sit above 50 MΩ at a few volts and collapse at several hundred.
Bars use a logarithmic scale: each step is ten times the last.
The 1577 applies the stress deliberately, then reports the leakage as resistance with ±(2.0% + 5) accuracy. For windings rated below 1000 V, guidance commonly cited from IEEE 43 calls for a 500 V DC test, which the 1577 covers; the same standard is often quoted for minimum readings of about 5 MΩ on random-wound windings below 1 kV and 100 MΩ on most form-wound windings, corrected to 40 °C. Treat those as reference points and follow the equipment maker's acceptance values where they exist. For the low-voltage checks the 87V can do, see how to check a motor winding for a short.
The 1577 as a multimeter: what you give up
The 1577 is an insulation tester with a meter attached, and its meter side is basic. It is True RMS, reads volts to 1000 V, ohms to 50 MΩ and continuity, and carries the same CAT IV 600V rating as the 87V. Beyond that the list is short: no capacitance, no frequency, no temperature, no Min/Max and no low-pass filter, so reading a drive's output voltage is harder than on the 87V. Current stops at 400 mA.
Worked from those lines on a 480.0 V DC reading with 0.1 V counts: the 87V allows 0.24 V plus 0.1 V, about ±0.34 V, and the 1577 allows 0.96 V plus 0.2 V, about ±1.16 V. Both are fine for checking a supply is present; only the 87V is suited to finer work on sensor and control voltages. We bought and tested the 87V, and its 4.8 rating reflects that; the 1577's 4.5 is desk research. More on the 87V's strengths in our Fluke 87V review.
No timed tests, no app: what the 1577 leaves out
The 1577 is the simple member of Fluke's insulation multimeter pair. It has no Fluke Connect radio, no stored readings and no timed polarization index or DAR test, and its range ends at 600 MΩ. For go/no-go checks before energizing, that is often all a procedure asks for: one reading at 500 V, compared with a minimum. For trending a motor fleet over years, it means a notebook and a stopwatch.
Where the 1577 sits
Fluke 1577 vs 87V: which should you buy?
| Your situation | Buy | Why |
|---|---|---|
| Service tech on live faults | Fluke 87V | 10 A, peak capture, low-pass filter, tighter accuracy |
| Contractor energizing new feeders | Fluke 1577 | 500 V check on new cable before first power-up |
| Pump and motor repair crew | Fluke 1577 | Go/no-go insulation reading before reinstalling |
| HVAC technician | Fluke 87V | µA flame-sensor current, temperature and capacitance |
| After a flood or long storage | Fluke 1577 | Wet insulation can pass an ohms test and fail at voltage |
| Plant tech doing both | Both | 1577 for isolated gear, 87V for running equipment |
| Trending a motor fleet with PI | Neither alone | Look at the 1587 FC instead |
If you only buy one, buy for the job you do most. Owning a 1577 without a capable DMM leaves you short on live diagnostics, while owning an 87V without any insulation tester only hurts if you sign off equipment. For broader shortlists see the best multimeter for electricians, the best multimeter for HVAC technicians and our multimeter buying guide. The 87V also has a sealed sibling, covered in Fluke 87V vs 87V MAX.
Safety: the 1577 puts 500 V or 1000 V DC on its leads
Choose the Fluke 1577 if…
- ✓You sign off motors, feeders or switchgear as fit to energize after work, storage or water damage
- ✓Your procedures call for simple 500 V or 1000 V spot readings, without PI timing or an app
- ✓You want insulation testing and basic volts and ohms in one CAT IV 600V tool
Choose the Fluke 87V if…
- ✓Your day is troubleshooting energized drives, controls and motor circuits
- ✓You need series current to 10 A, 0.01 µA DC resolution or 250 µs peak capture
- ✓Megohm tests are rare for you, or a colleague or contractor already does them
Neither if…
You need polarization index (PI) trending — neither meter logs it; step up to the Fluke 1587 FC.
The bottom line
Buy the Fluke 1577 if your work includes clearing de-energized motors, cables or switchgear to go back into service: its 500 V and 1000 V tests to 600 MΩ catch insulation faults no ordinary meter can. Buy the Fluke 87V, our hands-on tested pick, if your work is live troubleshooting: 10 A current, microamp resolution, tighter accuracy, a low-pass filter and peak capture. If you do both, carry both; if you need PI trending, step up to the 1587 FC.
Frequently asked questions
Can the Fluke 87V replace a megger?+
No. The 87V's resistance range tops out at 50 MΩ and uses a low test voltage, so it finds shorts and opens but doesn't stress insulation. A megohmmeter like the 1577 applies 500 V or 1000 V DC, which reveals moisture, contamination and cracked insulation that read as open on an ordinary ohms range.
Can the Fluke 1577 measure motor amps?+
Only small currents. Fluke lists 60 mA and 400 mA ranges, AC and DC, with no 10 A input, so a motor's running current is out of reach in series. Use a clamp meter for that. The 87V reads to 10 A, or 20 A for up to 30 seconds, and resolves 0.01 µA DC for flame-sensor work.
Is the Fluke 1577 a good everyday multimeter?+
It covers the basics: True RMS AC and DC volts to 1000 V, resistance to 50 MΩ, continuity and small currents, rated CAT IV 600V. Fluke doesn't list capacitance, frequency, temperature, Min/Max or a low-pass filter, and its DC accuracy is ±(0.2% + 2). As a daily troubleshooting meter, the 87V is clearly stronger.
What test voltage does the Fluke 1577 use?+
500 V or 1000 V DC, selected on the dial. Guidance commonly cited from IEEE 43 suggests 500 V for windings rated below 1000 V, so the 1577 suits most low-voltage motors and cables. It has no 50, 100 or 250 V setting for delicate control wiring; the 1587 FC adds those. One Amazon bullet says 550 V; Fluke says 500 V.
Does the Fluke 1577 have Fluke Connect or PI testing?+
No. Fluke lists no wireless for the 1577 and no timed polarization index or DAR test; those are 1587 FC features. You can time readings and divide them by hand, but its 600 MΩ ceiling often cuts off healthy windings before the 10-minute mark. The 87V has neither feature either.
Which is more rugged, the Fluke 1577 or the 87V?+
Neither is a sealed meter. Fluke lists the 1577 at IP40 (non-operating) and the 87V at IP30; neither rating covers water. Fluke gives the 87V a 3 m drop in one table and 1 m in its spec tab, and we found no drop figure for the 1577. For wet sites, look at the IP67 87V MAX.
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