Re: Home-Built Beam Balance

From: Lee Dammann <ldamnann_at_new.rr.com>
Date: Sun, 10 Dec 2006 02:53:48 -0000

Gary
Your right about the rigid pans and the possible error. I just went
down and put a 120 mg EZB motor stick on the pan. When moved all
the way in and all the way out on the pan, I can get a 10 mg
difference in weight. (+5, -5)
Hanging the balsa pan on 3 or 4 threads would be an easy fix. Thanks
for the heads up. Although in the back of my mind I knew there
would be an error, so I have always set the piece in the middle.

All your other ideas are great. Its part of the fun of a 2 dollar
homemade scale. You could but into it as much as you'd like.

I have fould that dampning is not necessary for what I'm doing. If
you keep the limit bars close, settle time is not bad. I would like
to have a centered pointer with scale so I wouldn't have to wait for
settle, just check that the ossilations are even on the scale.
You may also be able to put a magnet under the T-pin. With the
right strength and distance, it may be good enough. Something more
to play with.

Thanks
Lee
--- In Indoor_Construction_at_yahoogroups.com, dgbj@... wrote:
>
> LD,
>
> This is very good. Thanks for sharing it with us. Having the
pads glued to
> the bar introduces a serious error. Because the pads are rigidly
attached
> to the bar, placement of the object to be weighed will influence
the balance.
> Placing the object close to the blade will show a lower weight
than placing
> it farther out. Try it. The pads must be suspended with a
nonrigid
> attachment from a point on the beam.
>
> There are some refinements to consider.
>
> Trim nut. Having a machine screw with a nut on it sticking out
from the end
> opposite the scale will allow fine trim of the balance by moving
the nut
> along the screw..
>
> Vernier. A vernier is a small scale attached to the sliding
weight that
> allows reading one finer division of the scale. It has 10
divisions, but is
> 9/10 of the length of 10 scale divisions. If the index point on
the vernier is
> between two of the divisions on the scale, the subdivision
corresponds to the
> value where the vernier marks most closely approximates the
corresponding
> mark on the scale.
>
> Damper. The oscillation of the beam can be slowed with a
magnetic damper.
> A damper consists of a thin aluminum plate attached to the end of
the beam
> and a strong magnet near by. As the aluminum plate moves through
the magnetic
> field an electric current is induced. The induced current
opposes the
> magnetic field and exerts a force on the aluminum that is
opposite to the direction
> of movement.
>
> Gary Hinze
>
>
> [Non-text portions of this message have been removed]
>
Received on Sat Dec 09 2006 - 18:57:20 CET