Electronics > Projects, Designs, and Technical Stuff
mg scale - interesting effect
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Alex Eisenhut:
Maybe you can buy one of these just for fun

https://www.ebay.ca/itm/17Pcs-Set-211-1g-10mg-100g-Grams-Precision-Calibration-Weight-Test-Jewelry-Scale/202568482404?hash=item2f2a05be64:g:JTEAAOSwL-1cQCxh
Conrad Hoffman:
I own an old Mettler (H51ar) that can resolve 10 micrograms and use a modern solid state one at work with the same resolution. They're affected by just about everything and the electronic one is worthless if the room temperature is changing or with any kind of forced air heating or cooling system. The Mettler seems a bit more resistant. The fancy $5k one at work also has an option to zero out periodically if the reading is under some small value because drift is a fact of life. FWIW, the old Mettler is about as accurate as the fancy electronic one. There are all manner of "How to use an analytical balance" pages on the 'net and you'll find some interesting subtleties if you read them.
JBeale:

--- Quote from: Alex Eisenhut on March 24, 2019, 07:24:19 am ---Maybe you can buy one of these just for fun Ebay Weight Test Set
--- End quote ---
Indeed that looks like the same weight set that I have.  I don't have a standard to compare so I can't speak to the accuracy, but at least they read within 1% of their nominal values according to the scale.  The slippery plastic tweezers that are included with the set are awkward with the smaller weights and hopelessly inadequate to handle the larger ones, but you need some kind of tool to lower weights through the hole in the wind screen box on top of the scale. Dropping one of the larger weights on the pan probably won't be good for accuracy. Some larger steel tweezers (forceps?) with angled tips would do better, especially the kind with a grippy plastic coating around the tips.
helius:
The forceps are included because you really shouldn't touch calibrated weights with your hands, the oils can corrode them enough to change their mass.
I don't think those cheap weight sets are even F2 rated.
David Hess:
I have seen old calibration sets which included ivory tweezers for handling the weights.
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