> I have a need to know the position of a shaft, within one degree
> accuracy, that rotates at a speed of one revolution in two minutes. The
> shaft can only make one turn.

An off the shelf commercial shaft encoder would certainly work.

> I have been experimenting with a Hall Effect device (UGN 3503U) trying
> to count the teeth on the sprocket that turns the shaft. Although
> promising, I only get a one millivolt difference between the tooth and
> the gap and the Hall Effect device has to almost tough the sprocket.

Are you missing a premanent magnet in there somewhere?  It would be great
if the teeth were reliably magnetized, but that's unlikely.  You therefore
have to sense the presence of the teeth by how they alter an existing
magnetic field.

> To make matters worse, there is a lot of grease in the area.

That's no problem to a hall effect sensor.  This means you really don't
want to use optical means to measure the shaft position.


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