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| Oscilloscope Zoom Out Quirk |
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| EEVblog:
--- Quote from: Someone on May 10, 2020, 11:16:42 am ---The argument against always having full memory depth for single captures is what do you do when the pre trigger buffer isn't full yet, but the user pressed single? Throw away possibly the only trigger? --- End quote --- Ah, THAT'S the magic in the capture architecture design! This just triggered my memory! (pun of the week, surely?) I independently solved this in my DSOA Mk3 design back in 1998 with 7200 FIFO's. https://alternatezone.com/electronics/files/dsoamk3.txt |
| 2N3055:
--- 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 --- 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. --- End quote --- Digizer mode FIXES capture rate AND memory depth. With both at max, for instance, you get 400us of data on every trigger. Retrigger rate drops to 2500 trig/sec. No Peak detect mode, no Hires, no averaging. With timebase knob you cannot control anything except a window what are you looking at. It is not very useful or intuitive for G.P. interactive work. I presume it was introduced for data processing over SCPI. |
| EEVblog:
--- Quote from: nctnico on May 10, 2020, 11:22:41 am --- --- 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. --- End quote --- Err, wouldn't it apply to every scope brand that does this?, not just Keysight. How else would it be achieved whilst keeping any resemblance of half way decent update rate? |
| 2N3055:
--- Quote from: EEVblog on May 10, 2020, 11:27:43 am ---This just triggered my memory! (pun of the week, surely?) --- End quote --- :-DD |
| Someone:
--- Quote from: EEVblog on May 10, 2020, 11:27:43 am --- --- Quote from: Someone on May 10, 2020, 11:16:42 am ---The argument against always having full memory depth for single captures is what do you do when the pre trigger buffer isn't full yet, but the user pressed single? Throw away possibly the only trigger? --- End quote --- Ah, THAT'S the magic in the capture architecture design! This just triggered my memory! (pun of the week, surely?) I independently solved this in my DSOA Mk3 design back in 1998 with 7200 FIFO's. https://alternatezone.com/electronics/files/dsoamk3.txt --- End quote --- Not sure you solved it: --- Quote ---The RAM FILL period is required in order to allow the RAM to be at least half filled with data. This is to ensure that the data the PC reads back will always contain half pre-trigger information and half post-trigger information. If a trigger was to occur before the RAM is half filled, then we would have an indeterminable number of pre-trigger samples (if any at all). --- End quote --- Thats the same problem of what to do when the pre-trigger buffer isn't filled yet. With modern scopes having Mpts and Gpts of memory the pretirgger period can be substantial if you always have to fill it even when you are on a shorter timebase/memory setting. There are many intelligent things scopes could be doing to better manage their memory, improve update rates, and retain more data for review. But that will go against the manual control of everything users that are making so much noise here. |
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