Sniffity
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Anything wrong with this analytical balance?
Hey,
So I've been trying to pick up an analytical balance for my lab. Most prices I've found for 0.1mg precision balances are up in the thounsands. Yet
here I came across this:
http://www.ebay.com/itm/100x0-0001g-Lab-Digital-Analytical-B...
I was wondering if there's a particular reason why this one's so cheap. Can't figure it out.
Thanks for input!
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Sulaiman
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hidden cost
have you budgeted for a suitable callibration weight ?
OIML R 111-1: 2004 ........ class E1 (or E2 or ASTM E 617-97 (2008) .... class 0)
P.S. 0.1 mg in 100 g is 1 ppm ... bouyancy due to air density (1.225 mg/cc) comes into play.
Chinese eBay M2 weights in chrome finish are of variable plating quality, one of four 100g weights that I have is corroding 
[Edited on 24-10-2016 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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gdflp
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I haven't had good luck with Chinese equipment in the past. My recommendation, and what I did, is to look for a used analytical balance from a
reputable company such as Mettler or Ohaus.
I managed to snag a Mettler AE160 for $200, and they pop up for around that amount from time to time. It has a built in 100g calibration weight,
0-160g range, and 0.0001g precision.
Sure, it's a bit older, but it was a huge step from the $20 Chinese scale I was using before, and I've never had any reason to doubt the accuracy.
Never buy the "no further testing" balances though, or balances which don't have pictures of both a correct zero weight and accurate measurement of a
calibration weight, as they almost certainly are nonfunctional, or have missing load arms (talking from experience here .)
[Edited on 10-24-2016 by gdflp]
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Sniffity
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I'm between this two models:
1.-
http://www.ebay.com/itm/LED-Lab-Analytical-Balance-Digital-P...
2.- (listed above)
http://www.ebay.com/itm/100x0-0001g-Lab-Digital-Analytical-B...
Still, even factoring in the price of calibration weights, the price for the second one seems extremely, extremely low, when compared to say this one:
http://www.ebay.com/itm/OHAUS-Explorer-EX324-320g-x-0-1mg-0-...
Or this one:
http://www.ebay.com/itm/OHAUS-EX224-AD-AUTO-DOOR-EXPLORER-AN...
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Sulaiman
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Although digital scales such as the ones you are looking at are good, are they necessary ?
For chemistry, where the next most accurate measuring devices are class A volumetric glassware, with 0.1 % accuracy, why would you want greater
accuracy ?
Might it be better to have say three separate scales ?
e.g. 30g x 1mg and 300g x 10mg and 3kg x 100mg
probably with callibration weights <$100.
Three scales for 1/4 to 1/10 the cost, no fear of damaging expensive equipment, sufficient accuracy, and adequate range of weighing to cover most
experiments.
P.S. a 250 ml beaker of water at 25 C in ambient temperature of 25 C loses c1 mg/sec by evaporation.
(dry air at 0.5 m/s, if my calculations are correct 
So even if cooler and slightly humid air, you guys with 0.1 mg resolution scales should be able to watch/measure the weight decrease in real time.
O.K. ... now I want a precision balance
[Edited on 25-10-2016 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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Mush
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My friend has got this (300g model) at home. Not that bad compared to price. But the last decimal tends to shift after a few measurment , so I would
only count on the first and second decimal as an accurate reading.
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unionised
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Quote: Originally posted by Sulaiman  | have you budgeted for a suitable callibration weight ?
OIML R 111-1: 2004 ........ class E1 (or E2 or ASTM E 617-97 (2008) .... class 0)
P.S. 0.1 mg in 100 g is 1 ppm ... bouyancy due to air density (1.225 mg/cc) comes into play.
Chinese eBay M2 weights in chrome finish are of variable plating quality, one of four 100g weights that I have is corroding
[Edited on 24-10-2016 by Sulaiman] |
Not that it matters much to most people, air buoyancy comes into play at about 1 in 1000.
Once you have a balance that will weigh a 100ml flask full of water to a tenth of a mg you should be allowing for the variation of air's density with
the weather- temperature, pressure and humidity will make a difference.
So, the next question is:
How many people reading this habitually weigh things to 4 figures (or more), but don't do the buoyancy correction?
Incidentally, the reason you need a better balance than the glassware is that
1 you use it to calibrate the glassware (Not all class A is good to 0.1%, on the other hand, some is rather better) and
2 you can do gravimetric analysis to a better precision than you can do volumetric work.
[Edited on 30-10-16 by unionised]
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Sulaiman
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"So, the next question is:
How many people reading this habitually weigh things to 4 figures (or more), but don't do the buoyancy correction?"
me
CAUTION : Hobby Chemist, not Professional or even Amateur
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unionised
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| Quote: Originally posted by Sulaiman | "So, the next question is:
How many people reading this habitually weigh things to 4 figures (or more), but don't do the buoyancy correction?"
me |
And, most of the time, me- but at least I know I'm doing it. On a good day I can even work out if it's likely to matter.
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Mush
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These analytical balances are in an affordable price range too:
https://www.amazon.de/s/ref=nb_sb_noss/256-2373639-1493924?_...
G&G website:
http://pdf.medicalexpo.com/pdf/g-g/jj-bc/68544-152394.html
[Edited on 5-11-2016 by Mush]
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