I cracked the mystery of Chinese precision jewelry scales

[AVGresponding]

This is now a thing in on other scales. Got 10kg scale recently (there is at least two similar variations of it, one with grams in upper right corner and milk, and the one with grams in lower right corner). It weights nicely and seems accurate, but it rounds to every 100g. Rounding is such that anything more than 95g is rounded to 99g and anything more than 97g is rounded to 100g. similarly it rounds down above 100g.
(Attachment Link)
For more, see here
Scale also have calibration, and at least two secret menu, one to set scale capacity, one to set something for (60,120,180), maybe idle timeout, and one to set L00,L01,L02m but not sure what that is.

Interesting. I have some with exactly the same form factor, and the larger one definitely operates to 1g resolution, no rounding (beyond mg). It's 5kg max though and not 10kg. The smaller one similarly measures to 0.01g resolution to a maximum of 500g, though I don't have any calibration weights to gauge its accuracy. Weighing parcels before I take them to the Post Office shows the larger one to over-read by a percent or so, haven't had an opportunity to compare the smaller one yet.

[Whales]

My father recently bought a set of $19AUD 3kg 0.1 gram scales off eBay and has found them below promised spec.  Digikey, RS and E14 want hundreds for scales with similar written spec.

(1) There are multiple force sensors under the bed (presumably 4, one per corner) and if you shift your mass around to different positions then you can get more than 1g difference for a ~500g weight.

(2) It does the nonlinear lie trick near 0.0g, so you can't tare the scale and use it to compare similar masses.  The manual states that the minimum mass is 0.3g, perhaps that's what they mean, but it's clearly a software limitation (not a physical one).

Scale also have calibration, and at least two secret menu, one to set scale capacity, one to set something for (60,120,180), maybe idle timeout, and one to set L00,L01,L02m but not sure what that is.

L00, L01, L02 might be calibration coefficients for the individual load cells, assuming it has multiple load cells under different corners of the bed.  If there are three then maybe it only has 3 cells (triangle formation) or perhaps it has 4 and you cal 3 against 1 reference corner (square formation).

[DavidAlfa]

Are you weighting californium? ($27M/ gram)
You can't use whatever scale you want for trading purposes (Precious metals and such), so why is it sh** for a 14mg error?

What the hell do you spect from a cheap Aliexpress scale? https://www.aliexpress.com/i/1005005869570109.html

[miegapele]

L00, L01, L02 might be calibration coefficients for the individual load cells, assuming it has multiple load cells under different corners of the bed.  If there are three then maybe it only has 3 cells (triangle formation) or perhaps it has 4 and you cal 3 against 1 reference corner (square formation).

My 3kg 0.1g scale has only one load cell, so it's not that. This might be some backlight intensity I would guess, but not implemented.
But my scale is quite good, it's repeatable to 0.2g I would say, and has no weight differences wherever you place the weight.

[ebastler]

Are you weighting californium? ($27M/ gram)
You can't use whatever scale you want for trading purposes (Precious metals and such), so why is it sh** for a 14mg error?

I'm confused -- which post are you responding to? One of this year's posts or one of those from two years ago?

[DavidAlfa]

Haha true, I missed the date. Yeah to the original one

[Whales]

L00, L01, L02 might be calibration coefficients for the individual load cells, assuming it has multiple load cells under different corners of the bed.  If there are three then maybe it only has 3 cells (triangle formation) or perhaps it has 4 and you cal 3 against 1 reference corner (square formation).

My 3kg 0.1g scale has only one load cell, so it's not that. This might be some backlight intensity I would guess, but not implemented.
But my scale is quite good, it's repeatable to 0.2g I would say, and has no weight differences wherever you place the weight.

Perhaps they use the same firmware and electronics on a variety of models?

[thm_w]

Are you weighting californium? ($27M/ gram)
You can't use whatever scale you want for trading purposes (Precious metals and such), so why is it sh** for a 14mg error?

https://www.dea.gov/resources/facts-about-fentanyl

[DavidAlfa]

Not an expert in drugs, but that's why you never dose it in its pure form, it's just impossible. 2mg and you're dead.
So you weight 1 gram and mix it with let's say 1000g of another inert substance to make its concentration manageable.
Now, 1mg dose is 1g of product, a slightly overdose of 1.2g won't kill you.
The problem now is in the mixing homogeneity, must be absolutely perfect, or you'll risk taking the "spicy" salt pinch.
Not the scale problem, but the procedure.

Anyways, that's why you don't mess with fetanyl. It's like playing with a 100KV pole and a copper rod, "how close can I get?" LOL.

I got it administered several times during my long stance in the hospital few years back. I must say it's a hell of a drug.
Makes you feel in heaven, forget all problems, like when you were a child and it was the last school day before summer holydays.
Thankfully all I need to keep my mood is some ocassional nachos & bacon!

[cosmicray]

This is also true for calibration weights!
I bought a 1kg calibration weight on ebay a few years ago and it has a M4 set-screw in the bottom. So, naturally I took it out and wondered why there was a screw. Well, I found sand grains behind the screw to adjust the mass of the weight. And this weight was of the F1 class!
Unreal!

I have a couple of very old USPO/USPS manual scales here. They both have calibration adjustments like you describe. Never checked to see of there is sand inside. Both of them have dampening pistons under the bottom, which are supposed to be filled with whatever the manufacturer specified (which I was never able to discover). Seems like I put a thin consistency motor lubricant in them, and they work. The larger of the two is now approaching 60 years of age. Built better than a tank.