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At 07:15 AM 7/5/00 -0700, Sean McKeever wrote:
Just a note that PASCO scientific sells such alinear encoder. It is called
a rotary motion sensor ...
By definition, a rotary encoder is not a linear
encoder.
... and can be used with air tracks as yousuggested.
How do you turn rotary motion into linear motion?
Put a wheel on your air
cart? Or use strings as suggested below?
It also has many more uses and is one of the mostimportant sensors you
can purchase.
Agreed, shaft encoders are nifty things with many
uses. Nice versions can
distinguish the two directions of motion, cruddy
versions can't.
At 08:11 AM 7/5/00 -0500, Mike Moloney wrote:
One version of what John refers to is a 'shaftencoder'. We use these for
pendulum experiments, and many other applications.track. A light cord over the
They can be mounted as pulleys at the end of the
pulley gives the displacement of the cart vs. time.The resolution of the
encoders is outstanding - much better than sonicrangers.
I don't see a good way to get an accurate reading if
the cart changes
direction. The best thing I can think of is a loop
over two pulleys (one
at each end of the track) with the cart clipped to
the loop somewhere. But
I suspect that would perturb the cart a lot more
than the _linear_ encoder
I suggested. One also needs to worry about lash and
elasticity and lash in
the cords.
Bottom line: I still think a linear motion encoder
would be a cool
thing. It might make a good student project. If
anybody is interested let
me know.....