Re: Newall sperosyn encoders

--- In CAD_CAM_EDM_DRO@y..., ccs@m... wrote:

>
> 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 wasnt suggesting that the mag stripe be read with normal magnetic
heads. THe MR (magneto resistive)type heads will work with zero
velocity. These types of hearsds are used in the zip drives and
others I believe.

> 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.
> > >
> >
> >
> >
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