Re: encoders from servos?

Joe Vicars wrote:

> From: Joe Vicars <jvicars@...>
>
> What is a quadrature encoder and how do I know if I have one?
> I have a bunch of old servos and want to take the encoders off to make
>
> Lindsay's DRO. Are these the encoders I need?

If they are optical shaft encoders on servo motors, then they most
likely are
quadrature. Optical shaft encoders generally produce two signals with a

90 degree phase relationship, so you can tell not only distance
traveled, but
direction as well. Many have a 3rd channel which produces one pulse per

revolution, called the index pulse. For a servo motor application for
rotation
in only one direction, there might be only one pulse output signal.

Other position readout types are rotary inductosyn and resolver. These
generally require interpolation to produce sufficient resolution for
machine
controls.

Jon