General > General Technical Chat
I bought new bench scales (plus, discount code for Australian buyers)
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HighVoltage:

--- Quote from: Halcyon on July 15, 2021, 10:54:59 pm ---

--- Quote from: HighVoltage on July 15, 2021, 12:20:45 pm ---I found a really nice Mettler Toledo scale on ebay a few months ago. They are usually very expensive but I got a really good price.

It has so much resolution, it can detect the weight of a pencil line on a paper. Really impressive to see this for the first time.

--- End quote ---

I did look at MT as well. They make some really nice gear. But yes, quite expensive. Even the Wedderburn ones started to approach the limit of what I wanted to spend on a set of kitchen scales that I might use a few times a week, but they should last many years.


--- End quote ---
MT also has some not so expensive scales.
I bought a few of the ARIVA-MINi-S models.
They go up to 6 kg at 1 g resolution.
But with a "secret" menu found in the service book, one can turn on the 0.1g resolution and can weight up to 10 kg.

Halcyon:

--- Quote from: HighVoltage on July 16, 2021, 09:13:46 am ---
--- Quote from: Halcyon on July 15, 2021, 10:54:59 pm ---

--- Quote from: HighVoltage on July 15, 2021, 12:20:45 pm ---I found a really nice Mettler Toledo scale on ebay a few months ago. They are usually very expensive but I got a really good price.

It has so much resolution, it can detect the weight of a pencil line on a paper. Really impressive to see this for the first time.

--- End quote ---

I did look at MT as well. They make some really nice gear. But yes, quite expensive. Even the Wedderburn ones started to approach the limit of what I wanted to spend on a set of kitchen scales that I might use a few times a week, but they should last many years.


--- End quote ---
MT also has some not so expensive scales.
I bought a few of the ARIVA-MINi-S models.
They go up to 6 kg at 1 g resolution.
But with a "secret" menu found in the service book, one can turn on the 0.1g resolution and can weight up to 10 kg.

--- End quote ---

My understanding is that it's a limitation with the load cells and the graduations are just one aspect of the "accuracy". The way it has been explained to me is that a worst-case, accuracy is about 20 times the graduation. So if you have a scale capable of 0.1g graduations, the maximum error you can expect (on a calibrated scale) is +/- 2 grams. I'm sure some other people here can explain the science/technology behind it.

If you're able to "tweak" the settings, it might just be that the chassis/firmware is designed for a number of different models (as is the scales I bought) however the load cells are physically different. You might actually be throwing your scales more out of spec by overloading them and potentially damaging the load cells.
jpanhalt:
I have two types of scale: 1) Ohaus Scout (20 years old, 10 mg resolution) ; and 2) Various scales to 2 kg with 1-g resolution.

The latter are for cooking postage calculation and so forth.  I use the former for any other purpose, such a mixing adhesives.  If I could only have one, it would be the Ohaus.  A good wooden spoon can be used for estimating weights when cooking.

Just FYI, buying the latter was never a problem.  They are even available at Harbor Freight.  The former involved dealing with the DEA to insure I was not using it for an illegal purpose.  I was buying from a well known scientific distributor.  That may not be a problem with local/individual sales.  Or maybe, resolutions of <=10 mg have become so common that the DEA (USA) has just given up. 
jfiresto:

--- Quote from: Halcyon on July 16, 2021, 09:55:57 am ---My understanding is that it's a limitation with the load cells and the graduations are just one aspect of the "accuracy". The way it has been explained to me is that a worst-case, accuracy is about 20 times the graduation....
--- End quote ---

If I received a scale with up to a 20 count error, I would return it. I would want the reproducibility and linearity to be an order of magnitude better, or why distract me with the last digit?
Halcyon:

--- Quote from: jfiresto on July 16, 2021, 06:10:14 pm ---
--- Quote from: Halcyon on July 16, 2021, 09:55:57 am ---My understanding is that it's a limitation with the load cells and the graduations are just one aspect of the "accuracy". The way it has been explained to me is that a worst-case, accuracy is about 20 times the graduation....
--- End quote ---

If I received a scale with up to a 20 count error, I would return it. I would want the reproducibility and linearity to be an order of magnitude better, or why distract me with the last digit?

--- End quote ---

Apparently that's the way it is with these types of scales. Accuracy isn't necessarily linear. It's not a fault, it's a characteristic of how the weight is measured with load cells.

And I did say "worst case". With a decent set of scales, the error is likely to be far less. Cheap scales, well, who bloody knows.
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