Calibrating a Scale

Posted on January 13, 2013

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Recently, I made a semi-impulse purchase from the modernistpantry.  Among the various chemicals – which will go into various chocolates that you can’t have the recipe for (sorry) – I bought a scale that measures down to 0.01g.  I promise not to make recipes that specific for this blog.  Hopefully this scale will be useful in measuring spices for chocolates, etc.

So, I realized that I should have bought the 100g calibrating weight, when I realized there was no way for me to calibrate it.   I’m actually an OCD statistics person – so I started researching ways to calibrate it without a specified weight.  One person suggested water, but I don’t have accurate enough measuring devices to measure milligrams – nor do I have distilled water.

I have another scale, which doesn’t measure to that level of accuracy – so it wasn’t really helpful.

Apparently the right way to do this (which is questionable) – without a calibration weight – is to use currency in the form of coins.

Unfortunately we recently took our giant piggy bank (yes, it is really a pig) to the coin counting machine.  So I spent several hours scrounging change from various unused backpacks, purses, old coats, random piles of crap, and my bag of Euros.

This took at least an hour – probably more.

The random mix of coins made this into a really fun math problem, which got more interesting when I realized that the variance on coins is much greater than you’d expect (even accounting for crap the accumulate) – the mint should really look into that.  Another issue is that the weight of a US penny changed in 1982 – and it turns out penny’s kick around for quite a long time.  So that eliminated about half of the pennies I had.

Nickels – also seem to have gotten lighter in the early 2000s – though I couldn’t find any documentation on that.

So, once I eliminated the coins with an unacceptable variance, the problem got even more difficult.

So:

Euros

1 coin: 7.5g

0.50 coin: 7.8g

0.20 coin: 5.7g

0.10 coin: 4.1g

0.05 coin: 3.9g

0.02 coin: 3g

0.01 coin: 2.3

USD

0.01 coin: 2.5g (except pre 1982)

0.05 coin: 5g (except post 2000)

(dimes and quarters are useless weight wise since they aren’t a round number that can add up to 100).

So I need 100g.  The coins I have:

(2) 1.00 Euro

(1) 0.50 Euro

(5) 0.20 Euro

(2) 0.10 Euro

(1) 0.05 Euro

(2) 0.02 Euro

(3) 0.01 Euro

(8) pennies

(8) nickels

Solution:

Pennies (8) =20g

Nickels (8) = 40g

1 Euro (2) = 15g

E 0.10 (2) = 8.2g

E 0.05 (1) = 3.9g

E 0.02 (2) = 6g

E 0.01 (3) = 6.9g

=100g

Of course, thanks the the variances on the coins, it’s probably not well calibrated.  Sigh.

This penny doesn't weigh what it should OCD nightmare

after calibration - I changed out the nickels - and what do you know, they were different.  sigh

after calibration – I changed out the nickels – and what do you know, they were different. sigh

 

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