Re: Spherosyn

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

>
> majorityuk2000 wrote:
>
> >Has anyone looked at making Spherosyn type encoders and

electronics, or

> >know of any designs for them, please?
> >
> >
> I suppose you could look up the Newall patents and try to
> make one. It gives quadrature output at twice the period
> of the balls, so if you use 1/4" balls, you get a resolution of
> 1/8". Everything beyond that is done by interpolating. That's
> why the exact design of the coils in the sensing head is REALLY
> critical, because they are sub-interpolating the the balls to a
> high degree.
>
> Once you have the exciting and sense coils worked out, you
> could probably use the Analog Devices AD2S1200 resolver to
> digital converter. I think you'd end up with a resolution of
> .000122" if you can get the magnetics linear enough.
>
> You need to use magnetic steel balls in an aluminum or non-magnetic
> stainless tube. If the balls get magnetized, even the Newall scales
> become inaccurate.
>
> Jon
>

John,

Yes, I have their patents, which are very interesting, and the
original one expired. Looks quite hard to do. But thanks for the
pointer to the ADI resolver, I am constantly amazed by what magic
that company can do in "analogue" chips!

Cheers,

John H.