Calibrating a Postal Scale

I believe my postal scale is reading a bit high...
Does anyone know an easy way of calibrating it, say with coins or some other standard system of weights measure?
Beachcomber
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Lincoln cents from 1982 to date weigh about 2.5 grams.
from http://www.usmint.gov/about_the_mint/mint_history/index.cfm?action=coin_composition
3rd paragraph
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There's a set of new calibration weights on Ebay for a buy it now price of 20.00. Looks like an excellent deal.
http://cgi.ebay.com/NEW-16-Piece-Set-of-CALIBRATION-WEIGHTS-for-SCALES_W0QQitemZ7547144361QQcategoryZ48727QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
(and no, I'm not the one selling them)
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I don't know how your scale can be adjusted (2-point; single point...), but I believe a nickel masses 5.000g...
Hmmm...here's the specs...
http://www.usmint.gov/about_the_mint/index.cfm?flash=yes&action=coin_specifications
Beachcomber wrote:

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high...
say with coins or some

weigh it empty and set zero
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Beachcomber wrote:

Is your scale convertible to grams? A US Jefferson nickel weighs exactly 5 grams.
And I think 25 dimes weighs exactly 2 ounces.
Hope this helps, Bob
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Beachcomber writes:

Say you confirm the scale is off. Whaddya gonna do about it? It doesn't have any calibration adjustments or enough resolution to calculate a compensation.
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Richard J Kinch wrote:

Gees, Richard, you are suppose to be an engineer. Adjust it with a paper clip, make a mark, etc.
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George E. Cawthon writes:

You assume the error is linear, repeatable, and no hysteresis. Typically not the case. Compounded by digitization error.
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On Wed, 05 Oct 2005 21:23:57 -0500, Richard J Kinch

Thanks for all the good suggestions. I used the 20 nickles is about 100 g. reference and converted to ounces. (1 kg = 2.2 lb 16 oz = 1 lb).
As it turns out, the postal meter reads high, but just by a fraction of an ounce. I wonder if they construct it that way on purpose to "round up" the purchase of postage to the next oz, maybe to compensate for inaccuracies in other meters.
Beachcomber
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Richard J Kinch wrote:

Wow! You're right I never thought about hysteresis or digitization error.
I didn't assume anything, but apparently you assumed it was an electronic scale. Apparently you never heard of standard weights and interpolation.
Course the easiest solution for weighing light objects is a yard stick with a hole to hang it in the center, and strings to hold the weighed object and a known weight.
But I admit I'm a mess, I don't even consider parallax when I eat with a fork.
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If only you knew how much an ounce of water weighed....
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Goedjn wrote:

At what temperature?
Jeff
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(W1BSV + Brass Rat \'57 EE)
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Beach,
penny: 2.509 grams nickel: 4.995 grams dime: 2.263 grams quarter: 5.706 grams
Dave M.
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David Martel wrote:

Watch that. Real old (pre-1982?) pennies were three grams. Recent pennies I've measured at two grams. But yes, between the two periods they were 2.5 grams.
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If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.
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Beachcomber wrote:

You can use shot. Depends on the size as to how many make an ounce, but any gun store should be able to tell you. But I like the idea of coins. Any book on coin collecting will tell the size and weight of coins.
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Years ago, I took a scale down to the regional office of the U.S. Bureau of Standards, and they calibrated my scale for a five dollar fee, with a dated calibration stamp. I understand that state and county "weights and measures" will provide a similar service for a fee. For some businesses, such as produce departments of supermarkets, and gas stations, periodic calibration is mandatory. -Jitney
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