Yeah. While we're at it, how about being able to do a one-shot triggered
sweep, highlight a piece of the trace and say 'that's the trigger code -
every time you see this pattern, trigger'. Wonderful for looking at
stuff like composite video.

> ----------
> From:         John Payson[SMTP:supercat@MCS.NET]
> Reply To:     pic microcontroller discussion list
> Sent:         Friday, December 12, 1997 4:30 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: Oscilloscope Question
>
> > er,not quite. If the phosphor was long persistance every sweep would
> > remain on the screen. There is some sort of mesh inside the tube
> which
> > can preserve the scan when energised. Gradually the electrons leak
> away
> > and the trace fades. When storage mode is de-energised, the scope
> > reverts to normal display.
>
>
> I think the theory is that a very high voltage screen is placed near
> the
> phosphor, and that if a photon leaves the phosphor and hits the high
> volt-
> age screen it will knock off an electron (which in effect "recharges"
> that
> spot on the phosphor).
>
> I have actually used an analog storage scope once, but it was a bit
> trick-
> y to adjust.  Basically, there was a persistance knob which would set
> how
> fast the trace would fade.  If the knob was set too high, however,
> then
> the trace would start to "bloom" until eventually the whole screen was
> a
> solid glow.
>
> I think the thing must have had two screens, though, one inside the
> other
> since if memory serves it had a "Save" switch which would blank the
> display
> without disturbing the image on it; when you turned off the "save"
> switch
> the last-saved image would reappear.  I think the idea there was that
> the
> image would last longer if it didn't have to be swapping enough
> electrons
> for photons and vice versa to produce a visible picture.
>
> Kinda a fun gizmo, being able to set the persistence.  Personally, I
> sorta
> wish people could make digital scopes that did a better job of
> emulating
> analog ones.  For example, I'd like to see a scope that could
> (assuming
> moderate resolution, e.g., 10uS/div), store all of the following
> values
> for each pixel:
>
> [1] The minimum and maximum values observed during that time period,
> as
>     sampled.
> [2] The minimum and maximum values observed during that time period,
> if
>     run through a moderately low-pass filter (e.g. if each pixel is
> 500ns,
>     I'd like the filter's "effective" RC time constant to be about
> 100ns.
>     if the minima and maxima are logged every 10ns.
> [3] The average value observed during that time period,
> Gaussian-weighted
>     into the preceding and following ones.
>
> If the scope logged these five values, it could use them to show a
> waveform
> that was much more informative than that given by any mode on a normal
> DSO.
> Peaks would still be shown, but they wouldn't drown out the rest of
> the wave-
> form.  Also, since peaks would be stored in filtered as well as
> unfiltered
> form, it would be possible to estimate how much energy they actually
> cont-
> ained.
>
> Does anyone know if any scopes do anything like that?
>