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Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Calibrating a new digital scale on 02/08/2011 19:32:17 MST Print View

Many BPL people use a small digital scale to weigh their new equipment items. Many such scales have an auto-zero feature upon startup. However, to determine the linearity of a new scale, I wanted to measure some standards.

Toward the low end, a standard new U.S. Quarter coin weighs 5.670 grams. Mine passed that OK.

Now I'm looking for some standard closer to one pound (the top end for this scale). Any suggestions, besides a roll of quarters?

A pound of some food item is very inaccurate, because there are unknown wrappers involved.

--B.G.--

Stephen Bodiya
(stephen@bodiya.com) - F

Locale: Michigan
re: Calibration with Water on 02/08/2011 19:56:56 MST Print View

If you have an accurate way of measuring 16 fluid ounces of water, you could zero a container on the scale, add 16 fluid ounces of water and it should weigh approx 16.64 ounces.

I got approx 16.64 by using:
70*F water weighs 8.329 lbs per gallon. A quick google conversion gives approx 1.04 oz per fluid oz. So 16 fluid oz of water weighs approx 16.64 ounces (depending on how much you round the earlier conversions).

I don't know if this really helps since now the problem is finding an accurate measurement for 16 fluid ounces and I'm not sure the accuracy of a standard 1 cup measuring cup.

-Steve

edit:
I wonder if zeroing the scale (not knowing the exact bowl weight) for this experiment is problematic. It seems that it should still give you a good idea and wouldn't really make a difference unless the scale had an extremely non-linear relationship. i.e the heavier the item the larger % error.

Edited by stephen@bodiya.com on 02/08/2011 20:09:50 MST.

James S
(HikinNC) - F
Re: weights on 02/08/2011 20:12:28 MST Print View

Try a 1 lb fishing weight.

Christopher Taggart
(PennDude)

Locale: Western PA
re on 02/08/2011 22:04:53 MST Print View

Buy something at the grocery that requires them to measure the weight. Their scales have to be calibrated. Compare at home.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: re on 02/08/2011 22:27:04 MST Print View

I think the one-pound fishing weight sounds best, because it won't change much over time. Food would change over time.

I have a friend who runs a lab with a calibrated scale, and I can get the one-pound fishing weight checked there.

I'll head off to the fishing tackle store to look for a lead weight.

--B.G.--

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: Calibrating a new digital scale on 02/08/2011 22:27:20 MST Print View

Water and a graduated cylinder should let you know if it is close. 1 liter= 1 kilo, etc. A Nalgene will give you a good guestimate. You can buy calibrated weights too. Personally, I would just give it a rough check with a Nalgene and go from there. As cheap as they are, they do a good job.

James S
(HikinNC) - F
Re: weights on 02/09/2011 00:00:07 MST Print View

That's what I used, Bob. No guess work, no modifying, no issues with durability or weight fluctuation, and it's cheap (and multi use).

Devin Montgomery
(dsmontgomery) - MLife

Locale: one snowball away from big trouble
Re: Re: weights on 02/09/2011 04:52:22 MST Print View

Well, I was going to recommend a platinum-iridium cylinder, but it sounds like a silicon sphere may be more accurate.

Overkill?