FLUKE - 15B+, reliable, high-quality, expensive

After buying an expensive multimeter, I’d already thought about moving away from reviewing this kind of measuring instrument. But apparently my fascination with tools got the better of me, and when I saw an instrument from the well-known Fluke brand, I decided to get it for a review.

I’m almost certain most readers will say, “Why pay that much for an instrument when you can get something with the same capabilities for $10–15?”
And of course, they’ll have a point. If you want, there are plenty of cheaper instruments, some even with more features. But I’d divide multimeters into three categories:
1. Cheap knockoffs, clones of well-known mid-range instruments.
2. Branded mid-range instruments, such as Uni-T and Mastech.
3. Big-name brands: Fluke, Agilent.
Of course, the boundaries are fuzzy and sometimes overlap, but I think you get the general idea.

Instruments in the first category are usually bought for places where it’s easier to throw them away than repair them. They’re also an option for complete beginners in amateur radio.
The second category is mostly semi-professional gear. These instruments often have plenty of features and acceptable accuracy, but quality can sometimes be an issue.
The third category often consists of professional-grade instruments, where price is no longer a major concern and quality and reliability are what matter.

I’ve reviewed instruments from the first and second groups many times, as have others, but the third group has somehow been overlooked. There aren’t many reviews of these instruments, mainly for one reason: the price.
But since I can get an instrument to review, I decided to show you (and take a look myself) what a branded instrument is like—even if it’s made in China.

First, what is Fluke? By way of comparison, it’s like Hilti in the world of tools or Panasonic in the world of laptops.
The company was originally American, has been on the market for almost 70 years, and specializes exclusively in measuring instruments. One of its top-of-the-line instruments featured in this review.
Like many other companies, Fluke does some of its manufacturing in China. But that doesn’t mean the instruments are “Chinese”—quality control is still much stricter than in the cheaper segments.

I’ll jump ahead a little and show you an interesting table.
It shows that the only difference between the American and Chinese versions might be a single component, such as the battery compartment cover.


That’s it for the introduction. If you want more details, you can read about the company on Wikipedia. I’ll move on to the review.
Today’s review will mostly consist of photos, since there isn’t much to comment on :)

The box took a bit of a beating on the way, but it held up admirably to the postal services, being packed in a larger bag, and the flight.
Interestingly, the top of the instrument says “Not for sale outside China,” but that’s not going to stop us :)


On the back is a label listing the instrument’s main specifications and how it differs from the other instruments in this series.
There are three instruments in this series, each with different capabilities. When ordering, I chose the least expensive one because I figured temperature and frequency measurements weren’t important for an overall assessment of the instrument—and, in my opinion, they’re secondary features anyway.
By the way, one of the instruments has a rather unusual feature: it can test LEDs, checking whether they work and identifying their polarity. Otherwise, the more expensive models differ by adding temperature and frequency measurement.


General specifications:


I’ll hide the detailed specifications under a spoiler.

Interestingly, the meter comes packed in a tray made from recycled material. Eggs are often sold in trays like these, yet the box also included a pile of glossy printed documentation.
They saved money in one place and spent it in another :)


The package isn't just spartan; it's about as minimal as it gets:
1. Multimeter
2. Set of test leads
3. A pile of paper


A couple of words about the documentation included in the box.
There's a lot of it, though that's typical of expensive instruments—partly to make them look impressive, and partly for convenience.



Test leads.
I can't say I like them. The cable is a little stiff, and its diameter isn't very large, though maybe I'm just getting picky.
On the plus side, the design meets safety standards. The removable caps, when fitted, reduce the exposed, uninsulated part of the probes to just a couple of millimeters.


The multimeter.
My first impression when I picked it up was: it's heavy.
I wouldn't call it truly heavy, but for its small size it definitely feels substantial. That's a fact.


It's almost the same size as the Uni-T 61E and noticeably smaller than my 181A.
But the display is so easy to read—I appreciated that many times later. The digits are tall, and contrast is good when viewed from the front or side. It does drop when viewed from above, but in normal use the display is very clear.


The meter weighs 464 grams with the batteries installed.


For comparison, the 61E weighs 100 grams less despite being the same size, while the 181A weighs only 150 grams more.


The meter can of course be stood upright. The kickstand locks very firmly when closed and clicks quite distinctly when opened.
Of course, this is all true of a new meter; I expect it will loosen up a little over time.
The meter's rubber boot keeps it from sliding around on the table, which is a plus.


The display is shared across all meters in this series, and this model uses only a small part of its capabilities.
As I mentioned above, the digits are clear and large, which people with poor eyesight will definitely appreciate.


Controls.
There are three buttons at the top:
Blue — hold the reading.
Black — manual range selection
Yellow — enable additional measurement modes, marked in the same color next to the mode selector.

Below is another button for turning on the backlight. It's not very bright, and it's hard to show in photos; I'll demonstrate it in a short video at the end of the review.
The backlight turns off automatically after 2 minutes, a fairly convenient interval—much better than 15 seconds, as on some meters.

The mode selector also serves as the power switch, and the meter has an automatic shutoff after 20 minutes.
The operating modes are clear from the symbols. By default, the meter measures DC current/voltage (except on the top range, where the selector itself switches between DC and AC voltage); the additional button switches to AC current/voltage.
That makes sense, since I measure DC current/voltage more often, for example.
The markings are clear and easy to read.


There are the usual four input jacks, arranged in the usual way.
The gray jack labels on the black case aren't very easy to see; white, red, or yellow would have looked much better.


A full view, so to speak :)


As I said, the meter is wrapped in a rubber boot. The rubber is fairly soft and slightly textured, so it doesn't slip in your hand. And since the meter isn't very large, it's comfortable to hold.
There's a hole at the top for a special strap to hang the meter while you're working.
It's a shame they didn't include the strap, and only showed it and offered it for sale separately.


The battery compartment cover (available in two versions, English and Chinese) is secured with a twist-lock mechanism rather than the usual clips or screws. To open the compartment, turn the mechanism 180 degrees.
I tried opening it with a fingernail, which was very difficult, though possible; a flathead screwdriver is a better choice.


The meter runs on two AA batteries, which I think is better than the usual 9 V battery.
The claimed battery life is at least 500 hours of continuous operation, or about 2 months at 8 hours a day.
The compartment design is interesting: one pair of contacts is inside the multimeter, and the other is on the removable section. The cover fits tightly and locks firmly—perhaps a little too firmly, in fact.


The package included not only decent alkaline batteries, but very fresh ones too, with an expiration date in 2021!


The first thing I noticed when I took out the batteries was a small sticker with something about calibration written on it.


With a few simple maneuvers, we remove the meter from its rubber holster, since it can't be taken apart otherwise.


The top section lists the installed fuses, which is useful when choosing replacements.


Without its rubber cover, the multimeter looks much simpler and more compact. You can use it like this, and it might even be more convenient at home.


Undo the six self-tapping screws (four at the corners and two in the battery compartment) and we can get to the insides.


There'll be lots of teardown photos from here on, because I got a little carried away and was simply savoring the process :)
Everything looks excellent, and the first thing that catches your eye is the dark green color of the circuit board.
I've seen this kind of board in branded devices (including American ones); anyone who's seen one will recognize it.


The main measurement section looks like circuitry from the 1980s, but it's so beautifully and neatly done.
There's no need to mention that the flux has been washed off—but since I brought it up, I'll add that the board is spotless.


Strangely enough, the meter uses a chip-on-board IC, and this isn't a peculiarity of the “Chinese” assembly; I've seen reports that this can happen even in “American” units.


There are no trimmers in the meter at all; all calibration is done in software.
On the one hand, that's a downside—you can't change anything yourself. But it's also a plus: you can't break anything yourself either :)


The protection circuit for voltage spikes and overloads is just as neat and well laid out.
What's surprising is that this section has fewer components than in mid-range meters. Still, Fluke is said to have better protection. I can't verify that, so I won't argue the point.


Both current measurement inputs have fuses.
The only downside is that you have to take the meter apart to replace them; the manual says so too.


Current shunts for the two ranges, 10 A and 400 mA. I don't know whether there's a shunt for the µA range, or where it might be if there is one, since the shunts in the photo most likely correspond to two of the three ranges.


A look inside the meter.
1, 2. Two HC148 chips are installed. According to the datasheet, they're 8-to-3 encoders. I'm not quite sure what they're doing here, unless they're being used as switches.
A small op-amp is visible on the right, presumably for current measurement.
3. A flash memory chip is also visible, most likely storing the meter's calibration data.
4. The buzzer is just a buzzer, but I don't quite understand the marking. It seems to be rated for 12 V—surely not 1 V.


Eaton Bussmann series fuses. Excellent, high-quality fuses, just as I expected.
The fuses are rated for 440 mA and 11 A, while the specified ranges are 400 mA and 10 A, respectively.
Their maximum breaking capacities are 10 and 20 kA, respectively, which is quite substantial. The fuses themselves look as if they're made of woven material, though they're most likely ceramic.
Naturally, both fuses are rated for 1000 V, in keeping with the meter's stated safety category.


The fuse holders. Interestingly, an inductor is connected in series with the 440 mA fuse.


We remove the four screws securing the contact tabs to the meter's terminals. There are traces of paint on the screws, which should prevent them from loosening on their own. A small detail, but I haven't seen this on other meters.


We remove four more screws and take the circuit board out of the case.
You can also see here that the case is shared by all multimeter models in this series.


Tucked away at the side is a puzzling string of series-connected resistors with a total resistance of 1.001 MΩ. I think these are the input divider resistors, but I can't say for sure.


You can't see it in the photo, but the entire contact assembly is quite heavily greased. There's also grease on top of the selector dial.
Speaking of the selector, it turns smoothly and has distinct clicks, though I think all reasonably decent meters use exactly the same mechanism.
The moving contacts are arranged in some clever way that only the designers understand :)


There's nothing under the display, just traces. This explains why so many components are on the other side of the board: the designers didn't spread them across both sides.
You can also see contact pads for buttons, and I noticed unpopulated component positions on the back of the board.
But here's what's interesting: one version of the meter can test LEDs, yet there's no sign of a connector for hooking up LEDs. So the board may not be entirely universal after all.


The instrument fully disassembled, roughly in the order it was taken apart.


Let's put everything in a pile and move on to the tests.
The first test is perhaps not really a test, but just some additional information for users.
For this check, I measured a few parameters that might be useful. Here they are:
1. The instrument's input resistance is about 11 MΩ.
2. Voltage across the instrument's terminals when measuring resistance: 0.28 V
3. Voltage across the terminals in continuity mode: 0.53 V
4. Short-circuit current in this mode: 177 µA
5. Voltage across the terminals in semiconductor junction test mode: 2.35 V, enough for most LEDs.
6. Short-circuit current in this mode: 0.54 mA


Since I have a precision reference voltage source at home, the next test checks how accurately the instrument measures these voltages.
The board outputs 2.5, 5.0, 7.5, and 10.0 V. The measurement results are in the photo. In my opinion, they're excellent.
The board doesn't output exactly these voltages, but that doesn't matter for this instrument; it's easier to round the values.


Before the comparative tests, I ran a slightly unusual one: checking the maximum displayed value. The higher this value is relative to the specified limit, the better.
This instrument has a count of 4000, but it can reliably display up to 4397. I think it can reach 4399 too, but setting that value is very difficult.
That's 10% over the limit—excellent, no complaints at all.


Since I can't set exact values “to zero,” I simply tried to get as close as possible to the specified limit.
On the right are the readings from an instrument with a basic accuracy an order of magnitude better than the one under review. Of course, using a calibrator would have been more accurate, but I think this comparative test is more than sufficient.
The instrument fully met its specifications, with quite a bit of margin to spare.


The results for DC current are even better than for voltage, at least with this test method.


I'm still having some trouble testing AC voltage and current properly, though I think it's temporary. So I could only compare the readings when measuring mains voltage, and those look excellent too, in my opinion.


But the instrument let me down when I checked its capacitance measurement accuracy. I expected much better performance.
The error when measuring small capacitances could be explained by the fact that the instrument can't take relative measurements and therefore can't compensate for probe capacitance. But I don't understand why it overreads larger capacitances.

On the other hand, when measuring capacitors above 100 nF (and possibly from 20–30 nF), the readings are within tolerance.
For example, the manufacturer specifies an accuracy of 5% + 5 digits. That means a 725 µF capacitor (the reading on the meter at right) could read 725 × 1.05 + 5 = 766 µF. The display shows 749, which is perfectly fine.
When I tried to measure a 4700 µF capacitor, the instrument took a long time to think—so long that I got tired of counting the seconds and went off to do other things. In the end, it couldn't measure it; the instrument's upper limit is 1000 µF, which “isn't quite enough.”

More as an experiment, I checked a 10 mF capacitor with my Unit 181A. The instrument took a while to think, displayed “discharge,” then gave a reading a few seconds later.


The resistance measurement accuracy test will also be relative.
The reference meter has an accuracy of 0.05%, while the meter under test is rated at just 0.5%, so this test is more than fair.
At first I wanted to list the resistor values and their tolerances, but since their accuracy is also noticeably lower than that of the reference multimeter, at 0.5–0.25%, I don't see the point.
I can only say that the meter under review passed this test with flying colors, significantly exceeding its specifications. The error was mostly in the last digit, which you could say doesn't count at all.
Interestingly, when you short the probes, the meter first shows 0.3, then 0.2, then 0.1, and finally 0.0.
I don't know what this is, but it looks a lot like automatic zeroing. Since this feature isn't listed, though, I won't claim that it is.


Here's a short video of the tests.
First, I demonstrate the meter's functions and backlight, then the speed of its autoranging, and finally compare the ADC conversion speeds.
The difference from the Uni-T 181A is only 1.5 times, but it's still noticeable.
The meter under review takes 3 readings per second, while the Uni-T 181A takes just 2.
Sorry about the video quality. I filmed it with a slipper camera that was very awkward to hold.


And of course, here's a photo of it in my hand—it fits perfectly :)
It's comfortable mainly because the case isn't quite rectangular: it's narrower around the selector and wider around the display.


And, of course, the verdict.
Pros
Reliable
Accurate enough
Well-built
Good protection
Powered by two AA batteries
Long battery life
Backlight with a long auto-off delay

Cons
Large error when measuring small capacitances
The case has to be opened to replace the fuses
Very basic package
Price

My take: You may have noticed by now that “even the sun has spots”—even branded, expensive products have their drawbacks.
Even with these drawbacks, this is a genuinely good meter. Oddly enough, the key strength of this series isn't accuracy but reliability. People mainly like this brand's meters for their sturdy cases, good electrical protection, and near-indestructibility.
Of all the cons, the only one that really disappointed me was the large error when measuring small capacitances (up to 20–30 nF).
The other drawbacks are more a matter of design: the price comes with the brand name, the package is minimal, but you don't really need anything else, and while replacing the fuses is inconvenient, the manufacturer doesn't expect you to do it often anyway :)

That's all for now. As always, I'm happy to answer questions, take suggestions for tests, or just discuss the meter—sometimes the discussion is more useful than the review itself.
I asked the store for a discount on this meter for the review, and they gave me the GB32F coupon, which brings the price down to 69.99.


The product was provided by the store for review.