Products > Test Equipment

Oscilloscope Zoom Out Quirk

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nctnico:

--- Quote from: 2N3055 on May 10, 2020, 11:14:21 am ---Exactly. In real world less is less.
You keep forgetting to warn people that what you do makes scope retrigger at a very, very slow rate (few times per second). So you are looking at some edge at nanosecond scale, but your screen  refreshes few times per second or slower.

--- End quote ---
Again; that trade-off isn't there. Just set the memory shorter (or let the oscilloscope set it by itself). For example: the R&S RTM3004 can do it all.


--- Quote from: EEVblog on May 10, 2020, 11:10:38 am ---And perhaps that's a better description of this issue, "Capture memory depth in STOP/Single mode".

--- End quote ---
No, because that only applies to Keysight. So far only Lecroy and Siglent scopes can't record outside the screen. Don't be fooled by people who try to make capturing beyond the screen is something special. Most DSO do it except it seems very few people realise they (can) work that way.

nfmax:

--- Quote from: nctnico on May 10, 2020, 11:17:27 am ---
--- Quote from: Someone on May 10, 2020, 11:01:19 am ---
--- Quote from: nctnico on May 10, 2020, 09:40:59 am ---And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides. Just set the memory shorter one way or another and you have more waveforms/s and/or history / segmented recording.
--- End quote ---
Waveform update rate is limited by letting the acquisition length expand around the visible window, to claim there is no downside in doing so is plainly ridiculous. You like having manual control of memory depth and it expanding around the screen, we keep hearing this and get it, but your justifications are nonsense, and you throw it out as some big issue when it really isn't.

--- End quote ---
It seems your understanding of how an oscilloscope works is severely lacking. If you set the memory to a shorter depth then acquisitions take less time so you can achieve higher waveforms/s. I just want to have the choice between many waveforms/s OR using the full memory. I don't get why not having that choice is somehow better.

--- End quote ---

Hmm...

I think maybe just having a choice of how much acquisition memory to use is not enough. You need also to tell the scope if it should allocate memory to increasing the sample rate (for zooming in) or increasing the record length (for zooming out), and this should be independent of the X scale setting. I think the Digitizer mode of the X3000T works like this, though I have never explored it.

Someone:

--- Quote from: nctnico on May 10, 2020, 11:17:27 am ---
--- Quote from: Someone on May 10, 2020, 11:01:19 am ---
--- Quote from: nctnico on May 10, 2020, 09:40:59 am ---And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides. Just set the memory shorter one way or another and you have more waveforms/s and/or history / segmented recording.
--- End quote ---
Waveform update rate is limited by letting the acquisition length expand around the visible window, to claim there is no downside in doing so is plainly ridiculous. You like having manual control of memory depth and it expanding around the screen, we keep hearing this and get it, but your justifications are nonsense, and you throw it out as some big issue when it really isn't.

--- End quote ---
It seems your understanding of how an oscilloscope works is severely lacking. If you set the memory to a shorter depth then acquisitions take less time so you can achieve higher waveforms/s. I just want to have the choice between many waveforms/s OR using the full memory. I don't get why not having that choice is somehow better.

--- End quote ---
You can have the choice, more memory and fewer updates, or less memory and more updates. I have that choice too.

But you keep squeezing down the discussion to nonsense points:

--- Quote from: nctnico on May 10, 2020, 09:40:59 am ---capturing beyond the screen has no downsides.
--- End quote ---
It has a bunch of downsides! But you keep distracting people and adding noise rather than just presenting that as a tradeoff.

2N3055:

--- Quote from: nfmax on May 10, 2020, 11:15:02 am ---
--- Quote from: Someone on May 10, 2020, 11:12:19 am ---
--- Quote from: EEVblog on May 10, 2020, 10:56:35 am ---
--- Quote from: nctnico on May 10, 2020, 09:40:59 am ---And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.
--- End quote ---
It's only relevant if designing in this feature was done at the sacrifice of update rate in the design.
Obviously with Keysight having the fastest update rate and having this feature, that's obviously not a trade off that needs to be made in basic scope design.

--- End quote ---
Except they are mutually exclusive, the bonus full length capture of the megazoom scopes only occurs when there is another trigger after pressing stop. If you're trying to capture long record lengths of short bursts between infrequent events, pressing stop won't help.
--- End quote ---

You should use Single mode in that case

--- End quote ---

That is exactly the point. It is already invented, it's called SINGLE mode. No need to achieve it trough side effects.

nctnico:

--- Quote from: nfmax on May 10, 2020, 11:22:58 am ---
--- Quote from: nctnico on May 10, 2020, 11:17:27 am ---
--- Quote from: Someone on May 10, 2020, 11:01:19 am ---
--- Quote from: nctnico on May 10, 2020, 09:40:59 am ---And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides. Just set the memory shorter one way or another and you have more waveforms/s and/or history / segmented recording.
--- End quote ---
Waveform update rate is limited by letting the acquisition length expand around the visible window, to claim there is no downside in doing so is plainly ridiculous. You like having manual control of memory depth and it expanding around the screen, we keep hearing this and get it, but your justifications are nonsense, and you throw it out as some big issue when it really isn't.

--- End quote ---
It seems your understanding of how an oscilloscope works is severely lacking. If you set the memory to a shorter depth then acquisitions take less time so you can achieve higher waveforms/s. I just want to have the choice between many waveforms/s OR using the full memory. I don't get why not having that choice is somehow better.

--- End quote ---
I think maybe just having a choice of how much acquisition memory to use is not enough. You need also to tell the scope if it should allocate memory to increasing the sample rate (for zooming in) or increasing the record length (for zooming out), and this should be independent of the X scale setting.

--- End quote ---
For that some oscilloscopes have an 'automatic memory length' setting. That way it will tailor the amount of acquisition memory and samplerate depending on things like zoom mode. These aren't new problems; this has been solved decades ago.

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