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If you’re shopping for a Fluke insulation multimeter, you’re likely torn between the 1587 FC, the 1587/I400 FC with its included clamp, or the 279 FC that packs a thermal imager. The 1587 FC gives you PI and DAR measurements with TrendIt graphs, while the 279 FC adds a full thermal camera for finding hot spots.
This comparison is for electricians and maintenance techs who need to test motor windings, cables, and switchgear. The real trade-off is whether you want a dedicated insulation tester with a clamp (1587/I400 FC), a standalone meter (1587 FC), or a Swiss Army knife that also takes thermal images (279 FC). I’ll break down exactly which one fits your job.
🏆 Quick Picks — My Top Recommendations
Best Overall: Fluke 1587 FC
Best balance of insulation testing (PI/DAR with TrendIt graphs) and multimeter functions at 1000V — Check Price →
Runner-Up: Fluke 1587/I400 FC
Same insulation tester as the 1587 FC but includes the i400 clamp for measuring up to 400A AC — Check Price →
Best for Thermal Imaging: Fluke 279 FC
The only one with a built-in thermal imager — ideal for finding overloaded circuits and loose connections fast — Check Price →
I’ve laid out the most important specs side-by-side so you can see exactly how the 1587 FC, 1587/I400 FC, and 279 FC stack up against each other.
Full Specs Comparison
| Specification | Fluke – FLUKE-1587 FC FLU | Fluke 4692725 1587/I400 F | Fluke -279FC/IFLEX Digita |
|---|---|---|---|
| Brand | Fluke | Fluke | Fluke |
| Style | ✅ Fluke 1587FC Insulation Multimeter w/ Fluke Connect | 2-IN-1 INSULATION MULTIMETER W/CLAMP | Fluke-279FC/IFLEX |
| Power Source | Alkaline | Corded Electric | Battery Powered |
| Color | white | yellow | Yellow/grey |
| Item Weight | 300 g | ✅ 624 g | — |
| Measurement Type | — | — | ✅ Multimeter |
| Overvoltage Rating | — | ✅ CAT III 1000 V / CAT IV 600 V | — |
| Memory Storage | Fluke Connect Measurements App | Fluke Connect Measurements app | — |
| PI/DAR Measurement | ✅ Yes | ✅ Yes | — |
| Temperature Compensation | ✅ Yes | — | — |
| Thermal Imager | — | — | ✅ Built-in |
| Measurement Functions | — | — | ✅ 15 functions |
| AC Current | — | — | ✅ With iFlex |
The biggest difference I see here is that the 279 FC weighs just 1.8 pounds and includes a thermal imager, while the 1587/I400 FC packs a dedicated 400A clamp and weighs 624 grams — two very different tools for different jobs.
Individual Product Breakdown
I spent time looking at the specs, customer feedback, and what each of these Fluke meters actually does best to give you an honest breakdown of each one.
Fluke – FLUKE-1587 FC FLUKE 1587 FC 2-in-1 Insulation Multimeter
1000V max | PI/DAR with TrendIt graphs | 300 g weight | Fluke Connect compatible
This is the insulation multimeter I’d recommend to most electricians. The PI and DAR measurements with TrendIt graphs let you spot insulation degradation over time without guessing. At just 300 grams, it’s surprisingly light for a 1000V rated meter, and the Fluke Connect app saves your readings so you don’t have to scribble them down. My only gripe is that it doesn’t come with a clamp, so you’ll need to buy one separately if you want to measure current.
✅ Pros
- PI/DAR TrendIt graphs for tracking insulation health over time
- Lightweight at only 300g – easy to carry on the job
- Fluke Connect app stores readings and eliminates paperwork
- Rated for CAT III 1000V with 4.7 stars from 267 reviews
❌ Cons
- No clamp included – you’ll need to buy one for AC current measurements
- Upper temperature rating of 537°C seems oddly high for the meter itself
Fluke 4692725 1587/I400 FC 2-in-1 Insulation Multimeter with Clamp
Includes i400 clamp (1A to 400A AC) | 624 g weight | CAT III 1000V / CAT IV 600V | Fluke Connect compatible
- Pl/DAR measurements with TrendIt graphs
- Memory storage through Fluke Connect Measurements app. CAT III 1000 V / CAT IV...
- Temperature Compensation through Fluke Connect Measurements app
If you need a clamp, this is the one to get. The 1587/I400 FC is essentially the same insulation tester as the standard 1587 FC, but it bundles the i400 AC current clamp that measures from 1A all the way up to 400A AC. The 1 mA/Amp output makes reading easy, and the CAT III 1000V / CAT IV 600V rating gives me peace of mind on industrial panels. The trade-off is that it’s heavier at 624 grams and the clamp is corded, not wireless.
✅ Pros
- Includes the i400 clamp for 1A to 400A AC measurements right out of the box
- CAT III 1000V / CAT IV 600V safety rating for heavy industrial use
- PI/DAR TrendIt graphs and Fluke Connect app for data logging
- Amazon’s Choice with a 4.6-star rating from 175 reviews
❌ Cons
- Heavier than the standard 1587 FC at 624g – not as pocket-friendly
- The i400 clamp is corded, not a wireless iFlex accessory
Fluke -279FC/IFLEX Digital Multimeter with Built-In Thermal Imager with Iflex
Built-in thermal imager | iFlex current probe (up to 2500A AC) | 1.8 lbs | Fluke Connect compatible
- Full-featured Multimeter with built-in thermal imager
- 15 measurement Functions including: AC Voltage with low-pass filter, DC Voltage...
- Thermal imaging reveals many electrical issues quickly and safely, eliminating...
This is a completely different beast from the other two. The 279 FC is a full-featured multimeter with a built-in thermal imager that lets you see hot breakers and loose connections without poking around with probes. It includes the iFlex current probe that can measure up to 2500A AC in tight spaces. The downside? It’s not an insulation tester – you won’t get PI/DAR or megohm readings here. At 1.8 pounds and with only 18 reviews, it’s also the least proven option in this lineup.
✅ Pros
- Built-in thermal imager reveals overloaded circuits and hot spots instantly
- iFlex probe reaches tight spaces and measures up to 2500A AC
- 15 measurement functions including AC voltage with low-pass filter
- Fluke Connect wireless communication up to 20 feet away
❌ Cons
- Not an insulation tester – no PI/DAR or megohm measurements
- Only 18 customer reviews, so long-term reliability is less proven
- Heavier than the 1587 FC at 1.8 lbs
Which One Should You Buy?
I know that choosing between these three Fluke meters comes down to what you actually test day to day. Let me break down exactly which buyer each one fits best.
Fluke 1587 FC is right for you if…
- You need PI/DAR TrendIt graphs to track motor winding or cable insulation degradation over time
- You already own a clamp meter and just want a dedicated 1000V insulation tester that weighs only 300g
- You want Fluke Connect app compatibility for logging readings wirelessly without writing anything down
Fluke 1587/I400 FC is right for you if…
- You need one kit that does both insulation testing and AC current measurements from 1A to 400A
- You work on industrial panels with CAT III 1000V / CAT IV 600V ratings and want the included i400 clamp
- You’d rather buy a complete solution than piece together accessories later
Fluke 279 FC is right for you if…
- You troubleshoot electrical panels and want to spot overloaded circuits and loose connections with a built-in thermal imager
- You need the iFlex probe to measure up to 2500A AC in tight, hard-to-reach spaces
- You rarely do insulation resistance testing and want a general-purpose multimeter with thermal imaging instead
❌ Who Should Skip All of These?
If you only need a basic multimeter for home DIY or light automotive work, these are all overkill. You’d be better served by a simple check current price on Amazon meter and a separate non-contact voltage tester – these Fluke meters are built for professional electricians and industrial maintenance techs who need certified safety ratings and specialized features.
For the most common buyer – a professional electrician who tests motor insulation and also needs current measurements – I’d grab the Fluke 1587 FC and pick up a clamp separately. It’s the best balance of capability, weight, and value.
Frequently Asked Questions
Which is better for motor insulation testing — the 1587 FC or the 279 FC?
The 1587 FC wins hands down for motor testing. It has PI (polarity index) and DAR (dielectric absorption ratio) measurements with TrendIt graphs that let you track insulation degradation over time. The 279 FC doesn’t do any insulation testing at all — it’s a general-purpose multimeter with a thermal imager, not an insulation tester. If you’re checking motor windings, get the 1587 FC.
Is the Fluke 1587/I400 FC worth the extra money over the standard 1587 FC?
It depends on whether you need the i400 clamp. The 1587/I400 FC bundles that clamp which measures 1A to 400A AC, so if you don’t already own a clamp meter, it saves you from buying one separately. But if you already have a clamp, the standard 1587 FC gives you the exact same insulation testing features at a lower price. The clamp is also corded, so you’re not getting wireless iFlex convenience.
Does the Fluke 279 FC replace an insulation tester?
No, it absolutely does not. The 279 FC is a full-featured multimeter with 15 measurement functions and a built-in thermal imager, but it has no insulation resistance testing capability at all. You cannot measure megohms, PI, or DAR with it. If you need to test insulation on cables or motors, you need the 1587 FC or the 1587/I400 FC instead.
Which meter has the best safety rating for industrial work?
The 1587/I400 FC has the edge here with its CAT III 1000V and CAT IV 600V overvoltage rating, which is explicitly listed in the specs. The standard 1587 FC also handles 1000V maximum operating voltage. The 279 FC is rated IP40 but doesn’t specify the same CAT ratings in its specs, so for heavy industrial panels, I’d trust the 1587/I400 FC more.
Can I use Fluke Connect with all three of these meters?
Yes, all three are Fluke Connect compatible. The 1587 FC and 1587/I400 FC use the Fluke Connect Measurements app to store readings wirelessly and even apply temperature compensation for more accurate baselines. The 279 FC also communicates with a smartphone up to 20 feet away, letting you save both measurements and thermal images. All three eliminate the need to write down results by hand.
Which model is the lightest and most portable?
The standard Fluke 1587 FC is the lightest at just 300 grams, which is honestly impressive for a 1000V rated insulation multimeter. The 1587/I400 FC jumps to 624 grams because of the included i400 clamp and its corded design. The 279 FC is the heaviest at 1.8 pounds (roughly 816 grams), so if you’re climbing ladders or working in tight panels all day, the 1587 FC is the one to grab.
My Final Verdict
After comparing all three, the Fluke 1587 FC is my clear winner for most professional electricians. It delivers PI/DAR TrendIt graphs for insulation testing, weighs just 300 grams, and works with Fluke Connect at a competitive price point. The 1587/I400 FC is the runner-up if you specifically need the bundled i400 clamp for 1A to 400A AC measurements, while the 279 FC is a niche pick for those who want thermal imaging over insulation testing.
If you’re still on the fence, ask yourself this: do you test motor windings and cable insulation regularly? If yes, get the 1587 FC. If you need to see hot spots in panels more than you need megohm readings, then the 279 FC makes sense. Don’t overthink it — your actual daily work dictates the right choice.
Winner: Fluke 1587 FC
Best for electricians who need a dedicated 1000V insulation tester with PI/DAR TrendIt graphs and Fluke Connect logging. Lightest at 300g and the most versatile for the price.
Runner-Up: Fluke 1587/I400 FC
- Pl/DAR measurements with TrendIt graphs
- Memory storage through Fluke Connect Measurements app. CAT III 1000 V / CAT IV...
- Temperature Compensation through Fluke Connect Measurements app
Best if you need the bundled i400 clamp for 1A to 400A AC current measurements and want CAT III 1000V / CAT IV 600V safety ratings in one kit.
Third Place: Fluke 279 FC
- Full-featured Multimeter with built-in thermal imager
- 15 measurement Functions including: AC Voltage with low-pass filter, DC Voltage...
- Thermal imaging reveals many electrical issues quickly and safely, eliminating...
Best for troubleshooting panels where a built-in thermal imager and iFlex probe up to 2500A AC matter more than insulation testing capabilities.
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