Re: Air Track Ultrasonic

[Tom Ford <tomford@THESCIENCESOURCE.COM>]

The problem you describe is more often due to reflections coming from other
things in the neighborhood. Typically the glider is low to the track so the
sensor is down there too. Try a pylon of some sort on the glider so that
you can elevate the probe. A dime on the pylon should give you sufficient
reflection. In practice, the first thing that provides a reflection will
shut down the timing. As a glider moves along, different parts of it are
apt to be the reflection point of choice depending on the actual
orientation of the lobe coming from the probe. A little playing around,
moving the glider by hand, usually yields a solution. I regard any
ultrasonic whistling by the air track as urban myth/legend, even out here
in the sticks.

Tom Ford

At 08:14 AM 8/18/00 -0400, you wrote:
> In trying to do a displacement measurement of a sled on an air track
> with a CBL using an ultrasonic motion detector, I find that I get some
> rather erratic readings that end up giving a very poor velocity vs time
> graph.
>
> I am told that the air track produces ultrasonic sounds that confuse the
> motion detector.  Has anyone found a way around this problem if in fact
> this is what is throwing the data off?  Any suggestions welcome.
>
> Thanks,      Dave Abineri
>
>
> --
> David Abineri   dabineri@choice.net