Re: [CAD_CAM_EDM_DRO] replacing servo motor help >signal phase

Owen wrote:

>Thanks Jon,
>Now this isn't so open and shut. I don't have the skill or the equip to
>check what your are saying. I simply can't see how they could be so far out
>of sync and EXACTLY 180 deg out?
>
>I'll look to see if there is/are any marking like you suggest.
>Failing that, carefully remove the encoder and find a replacement.
>
>

OK, who is this tech? Is he from a company that supports CNC motion
control gear in the field, or is he a general electronic tech with no
experience
with servo encoders? If the latter, he could easily have been confused
by a differential encoder, and thought the encoder was hopelessly screwed
up. Are these encoders differential? If it has 4 or 5 wires, it must
not be.
If it has at least 6 wires, it may be differential. If it has 8 or 9,
it very
likely IS differential.

So, if this tech is not a CNC expert, and the encoder has 8+ wires, i might
not trust his tests. If the encoder has 4 wires and the guy works on CNC
gear all the time, you definitely need a new encoder.

Yes, I can think of several things (both mechanical and electrical) that
could
make the phase shift close enough to call it 180 degrees. Without extensive
laboratory gear, measuring the phase shift of an encoder is a very difficult
thing to do, so this "exactly" part is likely meaningless. And, commercial
encoders not built for ICBM inertial guidance won't give a 90 degree shift,
either. You are lucky to get the waveform to be within +/- 10 degrees of
true 90 degree quadrature on encoders costing less than $300 - 400.

Jon