"... it has the ability to "zoom" in on a portion of the
    trace."

Perhaps you are talking about "magnification" (X10 MAG)?

- where the x-axis drive to the CRT is simply multiplied
by a factor (usually 10) and the horizontal position control
is then used to position that portion of the waveform desired
for viewing on the visible portion of the screen?

     "It seems to me as though it just has
      to change the sweep rate during a
      part of the sweep in order to cause the
      zoom."

This would have been a pretty good trick to have
pulled off - if *only* TEK could have maintained a
linear sawtooth (used to drive the x-axis scope
plates) *while* also segmenting that original sawtooth
with a *secondary sawtooth* whose time and rate
was a precise fraction of the original ... very tough
to do with strictly analog circuits - *easy* to do
digitially ...

They *did* use two different sweep rates (and corresponding
sawtooth waveforms applied to the X-axis plates) in the
'delayed sweep' circuits - but the two traces were either
'chopped' or 'alternated' with the other "main" sweep.

Did I make any sense with the above? It's late - and I may not
have been very clear ...

Jim


----- Original Message -----
From: "Sean Breheny" <shb7@CORNELL.EDU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 30, 2001 9:08 PM
Subject: Re: [EE]: Scope Recommendation


> Hi all,
>
> Thanks for the scope recommendations, I'll check them out.
>
> I am curious about something, though. I have an old analog scope myself
> (Tek 7704A) and it has the ability to "zoom" in on a portion of the
> trace. However, I didn't think that was called "delayed sweep". What does
> delaying have to do with zooming in? It seems to me as though it just has
> to change the sweep rate during a part of the sweep in order to cause the
> zoom.
>
> Sean
>
>
> On Wed, 29 Aug 2001, Barry Gershenfeld wrote:
>
> > >It also has the ability to display
> > >both the entire trace and a zoomed view of the trace on the screen at
the
> > >same time, so it's really clear which section you are zooming on.  Why
they
> > >misnamed this "delayed sweep" though, I can't figure out.
> >
> > >I've never had a really good one before.
> >
> > There you go.  The "really good" analog scopes have a feature
> > where you can wait through part of the triggered waveform and
> > then fire off the second trace running at a faster sweep
> > to "expand" the view of a piece of the upper trace.  While
> > the second trace is running it highlights that portion of
> > the upper trace.
> >
> > Thus the name "delayed sweep".  Now being done digitally
> > and all that, and called "zoom".  But you wouldn't know
> > unless you'd seen one before.
> >
> > Barry
> >
> > --
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> >
> >
> >
>
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