Re: [CAD_CAM_EDM_DRO] Newall sperosyn encoders

Doug Harrison wrote:

> > 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.

Probably not, but maybe there is an LVDT read head that would be very
close to the right size. But, in fact, the coils are pretty easy to make.
Basically, you would have 3 coils in a row on the same form. the
center coil would be excited with a sine wave at 1 - 10 KHz. The length
of the coils would be contrived so the center of one outer coil would be
centered
over a ball while the center of the other outer coil would be centered over
the
gap between balls. This is where it gets complicated. You have to
analyze the amplitude and phase of the signals on the two sense coils.

Jon