Re: [CAD_CAM_EDM_DRO] Newall sperosyn encoders

The electronics are actually fairly straight forward and the same as used
with resolvers which are fitted to many CNC systems. The resolver is often a
brushless device which is excited by a sine wave (either 2.5KHz or 400Hz)
which is divided down from a high frequency source (~ 250KHz). The output
from the resolver is a phase shifted sine wave whose phase is proposrtional
to the angle between the rotor (the exciter) and the stator. The electronics
must be fairly simple as I have a weather vane using a resolver which I
built some time ago!!
The Spherosyn was as I remember able to use almost identical electronics and
its great advantage was that precision balls are readily available as they
are used in ball bearings. Compared with optical systems and the Inductsyn
which used to be very popular it was a breakthrough.

Regards Peter

----- Original Message -----
From: "Les Newell" <les@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, October 26, 2001 7:56 AM
Subject: Re: [CAD_CAM_EDM_DRO] Newall sperosyn encoders


> This was my first impression but LVDTs produce a varying voltage,
dependent
> on the position of the core. According to the documentation the output of
> the spherosyn sensor is a pair of sine waves of varying phase. They also
> mention that the sensor has six coils. I wonder what they are doing.
> The phase comparator circuit must be pretty clever as well. It has to have
a
> resolution of better than 1/1000th of a degree.
>
> Les
>
>
>
> > > In a similar fashion, a long flat steel bar stock could have an edge
cut
> > > with a sinusoidal pattern. This could be "read" by a Hall-effect
> > > sensor? Seems one has to induce a magnetic field in the "sine rack"
(or
> > > balls) in order to "read" them.
> > >
> > > Alan KM6VV
> >
> > Perhaps the Newall encoders use the balls as a variable core for
coupling
> > two coils as is done in an LVDT. It might be possible to cannibalize an
> > LVDT to get the read head.
> >
> > Doug
> >
>
>
>
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