On Tue, Jun 18, 2002 at 11:26:45PM +0100, Tony Duell wrote:
> > Wouldn't switching it on and off be many times more
> > efficient at producing a time-varying field? :-) .
> Isn't that one reason that those erasers run on AC?
AC makes a field that alternates its direction with constant peeks.
Moving the degauser away while it is running makes a field with
degreasing peeks. This is needed to actually degaus the media.
Switching the degauser off when it is near the media leaves the
media in a gaused state, possibly gaused in a way that a drive
gets confused or can't reformat the media. You need the alternating
and degreasing field to bring the hysteresis down to zero. If you
think of a magnetic hysteresis curve, you need a field that produces
a hysteresis curve that looks like a spiral. I.e. alternating with
degreasing amplitude. You can see this well when a monitor is
degaused.
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
Received on Thu Jun 20 2002 - 10:52:42 BST