Date: Tue, 07 Apr 1998 13:03:58 -0700
From: "Charles R. Patton" <pattonKILLSPAM@dt.wdc.com>
To: PSN-L Mailing List <psn-l@psn.quake.net>
Subject: Re: hand-held accelerometer
John Lahr posted:
> > > One of the new teachers at my school is looking for instructions for
> > > building some simple accelerometers in preparation for physics day at Great
> > > America. Can anyone help?
> > >
> > > Burt C. Kessler
I'd like to suggest something very simple. Take a piece of plastic
strip like a 1" wide piece of a plastic divider from a notebook, or a
vertical slice from a plastic milk bottle or pop bottle. A "straw" the
diameter of pencil lead from a plastic broom is still another
possibility. In any case, use one of these as a horizontal spring.
Take a small cardboard box and cut a square hole in it. Tape one end of
the "spring" in the box, horizontally across the hole with the end of
the spring adjacent to the edge of the hole on the other side. Now
depending on the strength of the "spring" you can add weights, such as
pennies, marbles, lengths of wire, etc. one unit of weight is so much
deflection, and then is marked on the edge of the hole opposite the
"spring". 10 units is so much more. If you leave the 10 units attached
permanently, you have just marked a scale in 0.1's of a G. Turn upside
down and calibrate in other direction. Now you have a plus and minus G
meter.
Refinements are to cover the hole with Saran wrap in order to prevent
drafts from bothering it -- those 30+ MPH winds on the roller coaster
can play havoc with the calibration. Cutting the hole with a radius to
match the "spring" will improve accuracy. Use of a strip of plastic
rather than a "straw" will confine its reaction primarily to be
perpendicular to the plane of the "spring", or even better, two "straws"
spreading apart to the attachment point -- a triangle when viewed from
above. The side rigidity would be excellent this way so sine/cosine
vector resolution of forces could be attempted.
Cheap, fast, needs no machining, test equipment, electric power, simle
to calibrate, and uses materials found around the house.
--------------------------------------
| box |
| --------------------------- |
| | | |
| | | |
| S | plastic | |
| C | "spring" | tape|
| A |==X========================XXXX|
| L | X | |
| E | weight(s) | |
| | | |
| | | |
| --------------------------- |
| |
| |
--------------------------------------
Regards
Charles R. Patton