Scales for very lightweight items, 0.001g-10g Scales.

These scales won't weigh a person or a stick of sausage, but they can (or at least should be able to) weigh things their “big brothers” can't.
So today we're taking a look at and testing a miniature scale for weighing very light objects.

First, what are scales like these even for?
Medicines, jewelry, and counting very small components.
They were originally intended for weighing medicinal ingredients, but that need has gone away, so they'll probably end up unused. I already have a more convenient 200/0.01 g scale for my everyday needs.

The scales come in a rather attractive box with a magnetic clasp. There are three versions, differing only in their weighing capacity: 10, 20, and 50 grams. This review covers the basic model.
By the way, when I looked for these scales on AliExpress, they were more expensive everywhere else—but that's beside the point.


Everything inside the package is quite neatly arranged, though in a way that's a downside: the more accessories they include and the better the packaging, the less money is left for the device itself.


The scales come with a manual, but unfortunately it's not much use: it's in English, one of the functions it describes isn't actually there, and another function isn't mentioned at all.


What I'm more interested in is the table showing the weighing range and accuracy. Since these scales go up to 10 grams, only the first two columns matter.
If I understand it correctly, the table says the display resolution is 0.001 and the accuracy is 0.005 grams. We'll check that later.
The package also includes tweezers of decent quality (at least for this application) and two calibration weights, 5 and 10 grams.


The scales are very compact, measuring 115 x 65 x 21 mm.


The top is covered by a protective lid, which isn't removable. Well, you can remove it, of course, but it's not designed to come off during normal use.


The scales are operated with four buttons:
Mode — switches between units (grams, carats, pennyweights, grains); press and hold to enter calibration mode.
PCS — supposedly counts items; the manual doesn't say anything about it.
On/Off — turns the scales on and off. They also shut off automatically after about a minute of inactivity.
Tare — zeros the reading.

The platform has a recessed area where the item being weighed is meant to go.


The platform has an L-shaped design.


There are four rubber feet and a battery compartment cover on the bottom.
The battery compartment is designed to hold four AAA batteries, but the scales run on just two cells. You can keep spare batteries or a little stash in the empty compartment :)


The first thing I tried weighing was, of course, a matchbox familiar to many.
I also tested my theory about where to place the item being weighed. There is a slight difference depending on where you put it.
By the way, the scales hold their readings quite steadily, with none of the last-digit fluctuations I expected.


1. The scale display has 5 digits and shows readings in the 00.000 format.
2. The PCS function is unclear. When I first switched the scales on with an item on the platform, they showed 25; I added more, and they showed 50. What 25 and 50 mean is anyone's guess. It even reminded me of a joke about Petka and the instruments (which is 300, and which are the instruments?).
But after pressing the button a few more times, the display showed -2008. So this function is still a mystery to me. The manual calls it something else, and apparently it serves a different purpose.
3. When overloaded, the display shows “Over Load.”
4. Holding the mode button for more than two seconds puts the scales into calibration mode. The power button doesn't work in this mode; to exit, hold the same button again. There is no information about this function at all.


Of course, I opened them up. Chronologically, I actually did this after the tests, but I'll describe the internals before getting to the testing process.
The scales are quite easy to take apart:
Remove the sticker on the bottom of the case; there's a screw underneath that secures the platform.
Remove the two rubber feet next to the same sticker and undo the pair of self-tapping screws.
Run something along the seam between the two halves of the case and release the two clips on either side of the display.


Everything inside is simple and reasonably neat, although in my opinion it would be pretty hard to make a mess with so few components.
Still, it's nice to see the circuit board made of fiberglass laminate rather than phenolic paper.


There's another screw on the bottom of the case that secures the measuring assembly. A similar screw on the opposite side secures the platform. I unscrewed it but didn't remove it.


While taking them apart, I wanted to move the display higher, since it's mounted noticeably off-center and the case partly covers the lower segments. But it wasn't easy to adjust, so I decided to live with it.
The backlight LED wires are visible on the left. The LED is very bright; you could easily reduce its brightness by about a third and it would look even better.


This photo shows the circuit board with a chip-on-board blob. I mentioned the circuit board material for a reason: this design is more likely to last if the board is made of fiberglass laminate.
You can also see the measuring assembly, which consists of a steel frame with strain gauges mounted on it.
The circuit uses a standard bridge configuration, a solution found in many scales.
The frame is marked KT702 -20C.
In general, you need to be careful when taking things like this apart, since strain gauges are quite easy to damage.


Well, how can you review a scale without checking its accuracy? That usually applies to any measuring instrument.

But instead of the familiar set of weights and standards, I used what you might call whatever I had on hand.
The thing is, I don't have any standards, but I do have a friend who has access to more accurate scales. He couldn't bring them over, so I had to use this sort of intermediate method.
I asked him to weigh a few items for me (many thanks to him for that) and label them. Obviously, this isn't ideal for long-term reference standards, but it works well enough for a few checks.
So, here they are:
Paper clip — 0.37080 g
Screw — 2.96860 g
Piece of metal 1 — 4.37110 g
Piece of metal 2 — 4.78105 g

It's worth noting that although the scales used to weigh the samples show five decimal places, they most likely (presumably) have a resolution of 0.00005 rather than 0.00001. Compared with the scales under test, though, this is insignificant.


Using various combinations of weights, I tested the scales from 0.37080 g up to overload.




Even without entering the data in a table, it was already clear during testing that the scales read slightly high. I tried weighing the included weights, as well as combinations of them.
The same thing again: readings were high.


Based on the combinations of verified weights and the readings obtained, I put together a table of the test results.
A brief note about the table.
Since I had to use combinations of different weights, this increased the uncertainty of the samples. The reference scales had an error of 0.001, so three weights could have a combined error of 0.003. Accordingly, I highlighted the tests that used combinations of two weights (yellow) and three weights (light green).
In any case, the scales failed to meet the measurement error specified by the manufacturer. They claimed an error of no more than 0.005, but the table shows a deviation of 0.015—three times the stated figure.


That's about it. Overall, I can say that the scales are very simply made, and the test confirmed my suspicion that it's hard to make a measuring instrument this accurate at this price.
That said, they do have a fairly convenient design, hold the reading well, auto-zero at very low weights (0.001–0.005), and come in attractive packaging.
But a test is a test, and it showed that in practice these scales are more likely to work with an accuracy of 0.01 g than the claimed 0.001 g.

Thanks to a tip in the comments, I calibrated the scales using the included 10 g weight.
Calibration —
Turn them on
Press and hold — Mode
The display shows — CAL
Press Mode again
It prompts you to place the weight (10 g in my case)
The display flashes, then shows — PASS
That's it.

The result is quite good.


I checked the weighing accuracy using the verified weights. Accuracy improved noticeably. But when weighing several weights—or, more precisely, adding them one at a time—the error still exceeds the claimed 0.005 g, though not by much.
But there's some instability. You can place a weight on the scales five times and get readings within ±0.002 g, then place it a sixth time and get ±0.006–0.007 g.


Out of curiosity, I tried weighing some tiny components.
I had no trouble with 1206-size capacitors, but 0805 components were trickier. I first put the resistors on the scale one at a time, but by the time I moved on to the next one, the scale had already reset to zero (automatic zeroing), so I had to put all three on at once.


I hope you found this review useful. As always, I look forward to your comments and perhaps some criticism of my testing method :)

The product was provided by the store for review.