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| Oscilloscope Zoom Out Quirk |
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| SilverSolder:
--- Quote from: 2N3055 on May 11, 2020, 12:01:21 pm --- --- Quote from: SilverSolder on May 11, 2020, 11:53:20 am --- --- Quote from: Wuerstchenhund on May 11, 2020, 11:11:17 am --- --- Quote from: SilverSolder on May 11, 2020, 01:57:48 am ---Imagine a camera with a zoom lens. An experienced photographer does not start with the lens zoomed out to the max, and then only zooms in from that point. Instead, they start with the lens zoomed somewhere around where their experience tell them is the best zoom factor for the kind of picture they are taking, then they trim the zoom both in and out a little bit from that point while watching the model in the viewfinder, until he/she looks "just right". It is a fast and fluid way of working with a camera. --- End quote --- Very bad analogy. Because optical zoom on a camera changes the resolution per scene area, so capturing pictures fully zoomed out will result in a loss of information when creating closer-ups from that 'acquisition'. On deep memory scope however, capturing long and zooming in does not result in a loss of information, because neither the vertical resolution nor the sample rate changes over capturing short. I can tell you that, if the loss of information (detail) wasn't a problem with zoom then many photographers would gladly capture fully zoomed out, because by capturing excess scenery they can later easily adjust the actual image size and position without having to go back to the place of scene and re-capture. --- End quote --- If you have enough RAM in the scope, of course I agree. But if you capture a "zoomed out" picture of a waveform on your scope of say, 10 seconds, just to pick an extreme, and your scope does not have enough RAM to capture that at full resolution, there is indeed a loss of quality compared to capturing a smaller time slice at a higher rate. That's my situation... --- End quote --- If you have short memory scope there won't be any data "outside the screen" either.. --- End quote --- There is off screen data as long as the timebase is running fast enough to use less RAM than what is required to display the image on the screen. So basically, the more RAM the scope has, the slower the timebase setting that the Megazoom off-screen idea will be work with... bottom line, more RAM benefits all scopes? |
| 2N3055:
--- Quote from: SilverSolder on May 11, 2020, 12:02:11 pm --- --- Quote from: Wuerstchenhund on May 11, 2020, 11:29:03 am --- --- Quote from: tv84 on May 10, 2020, 05:19:40 pm ---Gentlemen, you are ALL talking the same language! Nico starts with zoom in and likes to be able to zoom out. The others start with zoom out and like to be able to zoom in. It's all the same, but in reverse order. All the rest are just details (and personal preferences or lifelong habits)! --- End quote --- Unfortunately, it's not the same. "Zooming in" as in the standard method is done (you guessed it!) through the scope's zoom function. It provides references as for the position on the captured signal, can be displayed together with the full signal and works for single and continuous acquisitions. As to "zooming out", most scopes don't allow zooming outside the scope area. However, some scopes allow post-acquisition change of the timebase. Nico's method uses this as a means to "zoom out". However, it's not really a zoom, it's a change of timebase post-acq. And because it's a change of timebase post-acq, it *only* works if the scope is halted (i.e. no new triggers) and you can't display it together with the "zoomed in" view (well, you could probably use waveform memory, but you'd lprobably ose the timing information). So while the end result of both methods are the same in the cases where Nico's method works, they are *not* achieved the same way. --- End quote --- There is only so much real estate on the screen. If you already have 2 analog channels plus a handful of digital ones, using the zoom window becomes a bit of a pain (uses too much space) compared to just altering the timebase "post facto". Those multi-channel captures are also the kinds of scenarios where you most often end up looking for things that happened "off screen", in my experience at least. --- End quote --- Well, on R&S RTM3000 you can actually resize it . On Pico, you create views and size them at will. On Lecroy you can move and resize.... My problem with zoom mode on many scopes is also that it takes too much space. But that could be solved easily if we complain to manufactures long and loud enough. |
| nfmax:
Once again, may I point out that the 'zoom window' display (the equivalent of a dual timebase on an analogue scope) is not needed to zoom & pan either in or out post acquisition: just use the ordinary horizontal scale & position controls! |
| 2N3055:
--- Quote from: SilverSolder on May 11, 2020, 12:06:06 pm --- There is off screen data as long as the timebase is running fast enough to use less RAM than what is required to display the image on the screen. So basically, the more RAM the scope has, the slower the timebase setting that the Megazoom off-screen idea will be work with... bottom line, more RAM benefits all scopes? --- End quote --- I answered to your scenario: after you slow down enough you don't have enough memory for either one long timebase capture, or one short timebase capture with afterscreen data. And yes, for these kinds of problems more memory is more. But if you want to use it all the time, it makes scope slow. |
| 2N3055:
--- Quote from: nfmax on May 11, 2020, 12:10:30 pm ---Once again, may I point out that the 'zoom window' display (the equivalent of a dual timebase on an analogue scope) is not needed to zoom & pan either in or out post acquisition: just use the ordinary horizontal scale & position controls! --- End quote --- To make sure, for 3000T and Rigol that is correct. I don't know about the others. But I LIKE zoom mode. It gives me overview where in the buffer I am. Also on 3000T, I just use touch screen to move around... I just wish that zoom window could change size (to be little smaller if I want) when it get crowded. But, that is mostly because screen on 3000T is not very big. |
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