Dear piclisters,

What are good methods for measuring rotation rate?

I have a rotating device.
Currently I measure how fast it rotates using a
one-pulse-per-revolution optical sensor,
and then assume that it rotates at a fairly constant rate between pulses.

Lately I wonder -- is it really rotating at a constant rate?
Or are there significant angular accelerations and decelerations between pulses?

I think an angular rate gyro should be able to directly measure such
angular acceleration.
The fastest one I've found so far advertises "300 degrees per second!".
I suppose nearly 1 revolution per second is nice.
But my device spins around 50 revolutions per second.

I suppose some sort of rotary encoder (along with accurately timing
the width of each pulse) could possibly work.
But all the off-the-shelf rotary encoders seem to assume they are at
the center of rotation.
It would be more convenient if I could bolt something to the outside,
with a pattern ring about a foot in diameter glued to the stationary
part and a sensor bolted to the rotating part. (Or vice versa).
(Perhaps replacing, the one-pulse-per-revolution sensor I have now).

Suggestions?

-- 
David Cary
http://massmind.org/techref/member/DAV-MP-E62a
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