Re: [CAD_CAM_EDM_DRO] Newall sperosyn encoders

Les Newell wrote:

> Has anyone come across Newall spherosyn DRO encoders before?
> The scale appears to be a tube filled with steel balls and the position is
> sensed magnetically. They have some info on their website
> http://www.newall.co.uk/Spherosyn_Microsyn.htm but the description of how
> they work is a little vague. I wonder if this idea could be copied for a
> home-made DRO.

Yes, but! The trick is that they have to interpolate the result by a large
factor, since the basic resolution of the system is the diameter of the
balls, ie about 1/4". I imagine the coupling of the balls to a set of pickup

coils isn't too tough to work out, it is probably very similar to the design
of an LVDT coil, but the interpolation is not so easy. Analog Devices
makes some chips and chip sets that will excite and interpolate from
LVDTs, resolvers and inductosyns, but they are not cheap! The 1S80
and 2S80 series are the ones. I think you still end up with $80 of chips
per axis, minimum.

Jon