Re: linear motion encoder

[brian whatcott <inet@INTELLISYS.NET>]

At 06:45 7/6/00 -0500, you wrote:
> John Denker wrote:
>
> > The problem with a picket fence is that it is
> > insensitive to direction.  A lot of kinematics
> > experiments involve a change in direction....
>
> A commercial probe called "Smar Pulley" is a
> picket fence; it has a built-in photogate
> measuring instant spoke-couning rates.
>
> A more sophisticated probe, able to distinguish
> directions, is called "Rotational Motion Detector"....

> Ludwik Kowalski


Actually, picket fences are quite capable of sensing direction.
 You place a (relatively) stationary picket fence section before the photo
sensors and the moire pattern moves in a direction orthogonal to the
direction of motion. The moire is due to the modest inclination
in fence orientations. This angle can be optimized for positioning
the 'chiaroscuro' in the field of the sampling stationary section.


brian whatcott <inet@intellisys.net>
Altus OK