Re: [Phys-L] more prepping --> DIY scale

[John Denker <jsd@av8n.com>]

[sorry for duplicates]

On 3/9/20 12:45 PM, in a message with many good ideas, Dan Beeker wrote:

> • Build a mass scale out of rubber bands. How to calibrate it? How 
> accurate is it? How can you improve the accuracy without having to go
> out and buy stuff?

I know how to calibrate it.  Nickels!

The US 5¢ coin is metric:  The mass is 5 g and the thickness
is 2 mm.  The mnemonic is five cents, five grams, and five
per centimeter.

And no, it's not an accident.

If you ask at the grocery store they will probably give you
a roll of 40 nickels for $2.00.  Spend the ones that are
obviously old and beat up, or grossly dirty.  The ones that
remain are very good calibrators.

> • Build a mass scale/balance out of anything. What works best? Pros
> and cons of different ideas.

You can build a nice sensitive balance out of a yardstick.
Hard plastic is nice.  Metal is harder to work with, and wood
is more sensitive to humidity.

One option is to chuck up a sewing pin in an electric drill
and drill it into the yardstick, just above the centerline
(so the CM dangles just below the pivot, to give the thing
some tiny but nonzero stability).

Rig up little pans to hold the measurands (baling wire
technology again).

Protect it from drafts.