[Cwin]

I'm looking to start a home chemistry lab and probably one of the most important piece of hardware would be a balance. I figured I would need centigram precision so I went looking around on ebay.  I stumbled on some 100-300g/.01g precision for <$20. I looked around some science suppliers and balances are well in 100+ if I wanted to get a 200g/0.01g precision electronic balance. Are these cheap balances trustworthy or am I getting what I pay for?

[Cwin]

Okay so I went in for a AMW-100 because of the fairly good reviews it has and it's ridiculously cheap.
http://www.amazon.com/American-Weigh-AMW-100-Precision-Digital/dp/B0012LOQUQ/ref=cm_cr_pr_product_top

It came today and I tested it with some coins lying around the house.
Penny: 2.51
Nickel: 5.04
Dime: 2.27
Quarter (old, not with the states): 5.53

According to wikipedia, the mass of the respective coins:
Penny: 2.5
Nickel: 5.000
Dime: 2.268
Quarter: 5.67

The error with the nickel is reasonable. I don't know what happened with the quarter. Different states?
Anyways it seems to be a fairly accurate scale. It might be dirt cheap but it works fine for most purposes.

[billnotgatez]

It would be interesting to measure 7 of each coin.
Then do the mean and standard deviation.

[Cwin]

Alright I just tested it out. These coins were just some I had lying around the house. It would probably be much more accurate if I could get my hands on circulated coins and all from the same year.
Pennies: 2.50, 2.50, 2.47, 2.51, 2.51, 2.49, 2.53
Mean: 2.501
SD: 0.017

Nickels: 5.02, 5.06, 4.99, 4.99, 4.99, 4.94, 4.97
Mean: 4.994
SD: 0.035

Dimes: 2.31, 2.30, 2.25, 2.24, 2.25, 2.25, 2.25
Mean: 2.264
SD: 0.126

Quarters: 5.54, 5.30, 5.57, 5.60, 5.65, 5.73, 5.70
Mean: 5.584
SD: 0.132

[billnotgatez]

 

I could get my hands on circulated coins

Do you mean non-circulated new coins?

Does the WIKI article give standard deviations?

Just looking at your data - it appears you might be able to use coins to assist in shopping for scales depending on the accuracy you want.

Thank you for your efforts