Re: which commercial linear scale for EMC & S2G card?

[Ray Henry <rehenry-at-up.net>]

Doug

Perhaps some of the confusion comes from the difference between absolute
and incremental encoders or scales.  

An absolute encoder or scale spits out enough information to locate its
exact position anywhere while an incremental encoder or scale only spits
out a change in position.

I know that STG cards work with quadrature type incremental signals
regardless of the specific device (scale or rotary) but I don't know if
those boards can be made to work with absolute signals.  I suspect not.

Ray
  

At 02:36 AM 6/9/2000 -0400, you wrote:
>
>Jon Elson wrote:
>
>> Doug Fortune wrote:
>> > I'm sure this has been answered before (ie before
>> > I joined the list), but it looks like I will be needing
>> > to get direct linear feedback into EMC.
>
>> You need an encoder counter card.  The Servo-to-Go card is currently
supported.
>
>I am assuming we are talking about a linear scale attached directly to
>each axis.  I understand the S2G card can count encoder blips
>but I had assumed that was for rotary encoders only,  attached
>to the screw (and hence not guaranteed to be reading the position
>of the table).   You are implying that linear encoders do the
>same thing as rotary encoders,  and that the S2G is compatable
>with them as well.
>
>Or in other words, I am to find out whose 52" linear scales are
>compatable with S2G's card.
>
>**** Can someone save me the "experimentalism" and recommend a
>vendor for the linear scales (which has been tested successfully with
>the S2G cards and Linux/EMC) ?   *****
>
>> I believe that a cheaper, ISA-bus encoder counter card is either just now
>> supported, or will be, soon.
>
>Where can I find more information about the ISA encoder card?
>
>Tx
>Doug
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