Products > Test Equipment
Oscilloscope Zoom Out Quirk
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maginnovision:

--- Quote from: Wuerstchenhund on May 08, 2020, 08:12:56 am ---
--- Quote from: EEVblog on May 07, 2020, 11:19:25 pm ---
--- Quote from: nctnico on May 07, 2020, 11:39:40 am ---Well, this workflow (zooming out after a capture) is available on many DSOs. It is the standard (or at least configurable) on Tektronix, Rigol, GW Instek, R&S, the older Keysight scopes (DSO7000A / B series and derivatives), the original Siglent SDS2000 series and probably several others. However you have to realise that 'capture outside' the screen only works if there is memory left over after filling the screen. So it won't be the case at time/div settings where the maximum samplerate  is dropped. I have been using DSOs like this forever. I strongly recall being very annoyed by the Siglent SDS2000 not remembering this setting in the early firmware.
--- End quote ---

Sorry, I stand corrected, I had a brain fart, you are right. Both Rigol (2000) and (modern Megazoom IV) Keysight do this, they will capture full memory depth and allow you to "zoom out" from a shorter time base trigger capture.
Siglent (5000X) however does not do this, it captures the screen and that's it, you can't "zoom out" either in STOP mode or single shot triggered mode.
The Siglent sampling architecture must be implemented very differently.
--- End quote ---

Indeed, it seems the Keysight InfiniVision scopes perform the last sample at full max memory independent on the timebase.

The Rigols seem to do it when memory is set manually (well, the memory management is pretty basic).

However, Keysight Infiniium scopes (at least for DSO8k and newer) don't.

LeCroy scopes don't, and as Siglent follows LeCroy their scopes don't, either.

Tek MDO3k & Co do through a trick (leaving the timebase longer and zooming in when selecting shorter ones), other ones don't (I can't remember so I have to rely on 3rd paty info here).

R&S I don't remember but I don't believe they do.


--- Quote ---Through habit I guess I've just learned not to rely on this when capturing.

Now I'm curious to see a list of scopes that do this and those that don't. But this should have it's own thread.

--- End quote ---

Wouldn't this make a nice topic for one of your videos? Maybe coupled with a comparison of the nctnico method vs everyone else's method?  :-DD

I would watch that  :-+

--- End quote ---

Little late but it isn't just Nico's method, I've done this also. I typically generate my triggers onboard(cpld or fpga) then depending on how everything looks I may need to pull the timebase out to see more. If not great if so it saves me another capture. I can't see both things in one timebase easily since it's data and timing validation initially but if timing is good and data bad I have to see why. Waiting for another error could take time and slow down debugging as well.
2N3055:
Yes I did too. But that is not method. You were looking at stuff at wrong time base for that kind of analysis.
It is a lucky happenstance that scope, on it's own captured some more data than it was supposed to, so you could take a look at something else too..
And it worked in your favor. But it's not reliable all the time and on all time-bases. And different on every scope type.
I capture all in one long capture and can look at both slow and fast at will all the time.
That is how it's done if you were to use logic analyser for decoding. You capture the lot and zoom in into details..
nctnico:

--- Quote from: 2N3055 on May 08, 2020, 05:37:50 pm ---Yes I did too. But that is not method. You were looking at stuff at wrong time base for that kind of analysis.
It is a lucky happenstance that scope, on it's own captured some more data than it was supposed to, so you could take a look at something else too..

--- End quote ---
Sorry but you are trying to reason a moot point here. If you want recording outside the screen then select a scope which does. If not then don't. It has nothing to do with luck so don't try to ridicule a working method which is very efficient in real use cases. If you don't see it then you don't see it. As they say: you can lead a horse to water but it has to start drinking by itself.
2N3055:

--- Quote from: maginnovision on May 08, 2020, 05:48:39 pm ---In my case that's not true. If I pulled out initially to always see everything I'd spend more time calculating the timing measurements of the different signals than I would simply viewing the waveforms. Another issue I've run into is some scopes changing measurement resolution based on timebase in a way I lose the resolution I needed. I don't use $20k - $50k scopes though, I only need and use general purpose scopes. Maybe some more expensive scopes are better about that.

--- End quote ---
Thank you for explaining. That makes sense.
Proper deep memory scope is made exactly to work around this. And this is why I bought Picoscope. It works on full (not decimated) buffer.
It will keep resolution. It is cheapest analytical scope you can get. And decodes tons of protocols. Only problem is no protocol triggers. But i use it for bulk captures anyway.
2N3055:

--- Quote from: nctnico on May 08, 2020, 06:02:15 pm ---
--- Quote from: 2N3055 on May 08, 2020, 05:37:50 pm ---Yes I did too. But that is not method. You were looking at stuff at wrong time base for that kind of analysis.
It is a lucky happenstance that scope, on it's own captured some more data than it was supposed to, so you could take a look at something else too..

--- End quote ---
Sorry but you are trying to reason a moot point here. If you want recording outside the screen then select a scope which does. If not then don't. It has nothing to do with luck so don't try to ridicule a working method which is very efficient in real use cases. If you don't see it then you don't see it. As they say: you can lead a horse to water but it has to start drinking by itself.

--- End quote ---
If you want to capture outside screen, just don't. If you know what needs to be captured upfront, just do propper capture...
And leading a horse to water is a nice one. Thanks for that.  It applies nice to you who writes this outside screen nonsense EVERY SINGLE TIME anybody on EEVBLOG mentions oscilloscope.
Over and out.  I'm done here. I explained my opinion, explained how it applies to scopes I own and use. Rest is up to anybody else to form their own opinion.
And I don't want you to change what you believe and and contest what works for you. If you're happy with it, good for you.

All the best to all.
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