Re: [CAD_CAM_EDM_DRO] Resolvers vs Encoders

I'll try, altough Jon, could probaly do better.
A resolver can be a transformer with a 2 or more phase
primary. The secondary is inside the primary and is free
to move, some are linear, and some are rotary. The
Rotary ones usually use sliprings so the secondary can
rotate through a full circle (360). Being a analog
device the need something to convert them to digital.
The chips are rather expensive now, when I worked at
Entec, a new board cost between $500 to $1000 depending
on accuracy. a encoder can either be a "Absolute
encoder" (works just like a synchro with conversion
built in). These are usually VERY expensive and limited
in resloution. The second kind are "Incremental encoders"
these output a series of pulses as they are moved. If
they put out a pair of pulses streams with a phase
difference between the pulse streams can be used to
determine the direction of movement.
Now that this is as clear as mud, I'll let Jon or
someoone else clarify it.
Bill Higdon
PS you can convert a syncro machine to a eincremental
encoder machine, by replacing the syncro's with suitable
encoders. I did one upgrade (conversion)like that while
at Entec.

> Hi All:
> Can any of you explain to me, the differences between resolvers and
> encoders.
> What is the implication for machine performance?
> Is a retrofit from resolvers to encoders a worthwhile effort?
> When did resolvers go out of favour and why?
> I'm casting amorously about, for small CNC turning centers, and I've heard
> the terms mentioned, especially in regard to Hardinge machines.
> Mid eighties machines seem to be the transition point from the resolver
> system to the encoder system.
> It looks to me like there is a fair amount of very nice old CNC iron from
> that era out there available for very little money...certainly far less than
> building from scratch or retrofitting a manual machine...especially when you
> consider that the enclosures, the coolant pumps, the ballscrews, the way
> covers etc, etc are all already there.
> Cheers
>
> Marcus
>
>
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