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Oscilloscope Zoom Out Quirk

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nctnico:

--- Quote from: tv84 on May 10, 2020, 11:53:22 am ---
--- Quote from: EEVblog on May 10, 2020, 11:17:42 am ---This is why Keysight are clever in how they do it. They know that in trigger/Auto continuous update mode you don't care about extra data outside the screen, you just want the fastest update rate possible. Only when the user specifically requests STOP or Single mode does the scope then go "a-ha, I don't care about update rate any more, so I'm going to make one last capture using all my available memory, just in case the user wants to do a zoom outside the display window. And I pay no penalty do doing this! Ain't I clever!"

--- End quote ---

(Disclaimer: I'm in no position to argue this theme with all the gurus here but, having said that,...)

If that is what KS does, and others don't,  I don't understand why.   :-//  We're talking STOP and SINGLE modes, right? So the scope has all the time in

--- End quote ---
No. When using single mode you'd need to press the single button every time. In case of slow events (which can be generated manually) it is much easier to press stop when something of interest appears on the screen instead of having to bother with the oscilloscope all the time. And you only have two hands. Starting something on the DUT and holding a probe already needs 2 hands.

Someone:

--- Quote from: Someone on May 10, 2020, 11:57:48 am ---The expansion around the screen is mostly (entirely?) symmetric on the mega zoom "bonus" capture, like the middle example. There is no control over where the extra memory is allocated, either for this, or nctnico's case where they manually set the acquisition memory depth wider than the visible window.
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--- Quote from: 2N3055 on May 10, 2020, 11:58:49 am ---When you press STOP, 3000T seems to reconfigure and capture one SINGLE capture on a separate trigger, together with pre trigger time. On highest sampling rate, you always get 40us pre and 360us post trigger.
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Another inconsistency, you making me crazy...


--- Quote from: 2N3055 on May 10, 2020, 11:58:49 am ---EDIT: Actually it depends on the where is trigger reference point set. If you set hor.ref point left, than it is -40us/+360us. BUT, if you set hor.ref point to center, than captured buffer is -200us/+200us arround trigger point. Respectively, if you set hor.ref point to right you get -360us/+40us

--- End quote ---
Phew! I thought it was mostly symmetric (generally working with symmetric trigger setups), thanks for the extra details. Its far too fiddly to rely/plan on any of that, I just use a scope as it works.

nctnico:

--- Quote from: Wuerstchenhund on May 10, 2020, 12:04:21 pm ---Personally, it also doesn't fit me because it sounds a bit arbitrary (like blindly poking around in some circuitry), as I tend to think about what I want to measure and what I expect to see, and then setup the scope accordingly. But that's just me (although most of our engineers are the same "think before you do" types). But hey, whatever fits you best.

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But you don't know what you don't know. If you are looking for a bug you start with a blank slate. So how are you going to setup your scope if you don't know what you are looking for? If you already know what a signal looks like there is no use measuring it. Often something interesting turns up which makes me want to see want came before and after. There is no way to know until there is something on screen. Maybe you'll capture it again after an hour. Same goes for design verification. Something odd may pop-up. It is nice if you don't have to recapture to see the rest but just zoom out. In some of my cases it can take several minutes to make a new measurement.

And there are also cases where it is just quicker to capture something visually rather than setting up a complex trigger condition. Remember my way of working stems from saving time & effort.

Come to think of it: it makes no sense needing to use zoom mode to have all the memory available. I already told the oscilloscope to use a certain amount of memory.

Anyway, it seems that you have a very narrow view of how an oscilloscope should be used and are unable to see beyond that to streamline operations. It reminds me of my chief when I was working in a chocolate factory: 'you must carry those trays with both hands because god gave you two hands'.

Wuerstchenhund:

--- Quote from: Someone on May 10, 2020, 12:05:05 pm ---Zoom windows are a way to set the size of the full acquisition, the trigger point within that full range, and still see some short timescale detail in realtime.
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Indeed.

The other thing is that zoom, after all, is actually just a math function ('window' function) over the acquired waveform, and on better scopes you're not limited to a single zoom mode but you can actually have multiple, each zooming into a different part of the signal, all showing live data if you want.

These zoom modes can then also be used as an input for further analysis.

Which means zoom mode is just more than just stretching the displayed signal segment.


--- Quote ---It ticks all the boxes for nctnico's bizarre use case except they then added another constraint of "zoom takes up too much of the display" which sounds like a good excuse to consider scopes with better display management and higher resolutions.

--- End quote ---

I agree, this is just a case of a poor UI on a particular scope, not a problem that's inherent to zoom as a function.

2N3055:

--- Quote from: Someone on May 10, 2020, 12:17:09 pm ---Phew! I thought it was mostly symmetric (generally working with symmetric trigger setups), thanks for the extra details. Its far too fiddly to rely/plan on any of that, I just use a scope as it works.

--- End quote ---
Exactly my point.

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