Re: [CAD_CAM_EDM_DRO] Re: Newall sperosyn encoders

I don't believe you can read magnetic tape with the normal heads
unless it is moving in relation to the readhead. Ie, there is a
current induced that is dependent on the rate of change of the
magnetic field. If you were moving an axis at extremely low velocity,
the induced current could well be too small to detect. It may work
under normal use, but I'd be afraid it would miss any kind of slow
creep, say in an axis that was nominally locked...

I think the balls-in-a-tube system works inductively - ie, the read head
generates a changing magnetic field and determines how much ferrous
metal is inside the tube there. Balls are used because they can be
cheaply had at great precision - just drop them into precision drawn
tubing (or maybe even force them into slightly undersize tube) and
all the hard stuff is in the read head.

Chris

> That a damn good idea Bill! Should make for much more accurate table/
> spindle positioning as well.
> Wonder why someone hasn't done something about it yet. As I recall from my
> original computer repair training back in '75 that's how the old streaming
> tape drives were positioned. Couldn't one of those drives systems be
> adapted for this purpose?
>
> Smoke
>
> >
> > I also suggested using a MR head to read a magnetically encoded
> > scale in a similar fashion to a credit card encoding. Encoding
> > magnetic tape with the bits would be fairly easy if someone could
> > work out the readheads.
> >
>
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>