Products > Test Equipment
Oscilloscope Zoom Out Quirk
Gandalf_Sr:
Actually, I need to clarify. After the capture is done, turning the horizontal time control to zoom out shows the captured memory area in the little zoom window top center. At some point, 5 mS/div, it clearly runs out of displayable data and the picture doesn't change even though the indication of the x axis time does - which seems like a bug to me as you could end up looking at a display where the x axis time shown isn't correct for the displayed trace.
2N3055:
--- Quote from: nctnico on May 09, 2020, 03:17:44 pm ---
--- Quote from: Gandalf_Sr on May 09, 2020, 02:57:03 pm ---Give me a specific test to try and I'll run it on my MSO5074
--- End quote ---
Set the oscilloscope to 100ns / division, set the memory depth to the maximum number, connect the probe to the calibrator output, set the trigger level to trigger on the signal, set the scope to run mode, disconnect the probe (so no more trigger events; do not press stop!), turn the time/div knob to 200ns/ division. If you get more signal then your scope supports recording beyond the screen.
--- End quote ---
In that case, if that is criteria (not pressing STOP) Keysight 3000T doesn't capture anything outside screen in normal mode.
Only when set to digitizer mode, in which case it becomes little wierd to setup, and is not really how you want it for normal interactive mode....
Set to 100ns / division, burst from siggen, trigger set to normal, waiting for next trigger in RUN mode, STOP not pressed:
Still waiting for next trigger, timebase expanded to 200ns / division
This shows what I'we been explaining. 3000T is capturing only screen full of data from trigger to trigger. It is only when you press stop that it will reassemble some data before begin of the screen, and it will keep capturing until it runs after memory. What I suspect is that it literally goes from RUN to STOP, by capturing one SINGLE capture on next trigger after you press STOP (Just with half of the buffer because of state of capture engine at the time, the ping-pong buffers).
I presume it behaves like that, because, if press stop now, while it's waiting for next trigger, it doesn't get any additional data:
So Keysight 3000T can't be used that way, unless it is in DIGITIZER mode, that makes using scope weird for interactive use, negating all user friendliness and ease of use Keysight is famous for.
I would presume all current generation Infiniivision scopes will have same behaviour (chipset related).
If anybody needs any other test, let me know.
Regards,
Gandalf_Sr:
A further test...
1. Set up a decoder for RS232 at 230,400 Baud on Ch1 with correct polarity and threshold level.
2. Press the mode button until (Normal) appears on the screen briefly
3. Press [Acquire] and set memory depth to max (200M in my case)
3. Monitor RS232 signal with probe and then disconnect to see data frozen on screen with decode data shown below trace
4. start zooming out and notice that top center zoom window (if that's what it's called) is mostly white (that white represents captured data) and there's a small black area that moves as you scroll left and right. It gets bigger as you zoom out and it's indicating the area that's shown on the main screen.
5. In this test I was able to see oodles of data before and after the trigger point and it was all decoded as I looked at it on the main screen
That was fun :D
Gandalf_Sr:
..and I can do the same in Auto mode or if I press Stop, or if I do a single trigger. There is a boat load of data captured and it's either side of the trigger point.
[EDIT] But it only does this if I manually set the memory depth to max; if the memory depth is set to 'Auto' then the behavior is just like the pictures posted by 2N3055
egonotto:
Hello,
some pictures from RTA4004.
If you want samples outside of the windows you can use a fix memory size.
If you use auto it can be samples outside windows but not in all cases.
Best regards
egonotto
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