Oscilloscope Zoom Out Quirk

[Gandalf_Sr]

Well you learn something every day 

[Martin72]

So what we know now is, that some scopes can do the "nico way", others don´t.
Does it bother me ? No.
Apart from this I wonder, what siglent will do with it´s waste amount of memory ( 200MP/250MP SDS 2K+/SDS5K) when only could used in lower timebases.

[2N3055]

So what we know now is, that some scopes can do the "nico way", others don´t.
Does it bother me ? No.
Apart from this I wonder, what siglent will do with it´s waste amount of memory ( 200MP/250MP SDS 2K+/SDS5K) when only could used in lower timebases.

Use it for always running history mode that is very useful. Or segmented (sequential in Siglent parlance) acquisitions.

[Someone]

So what we know now is, that some scopes can do the "nico way", others don´t.
Does it bother me ? No.
Apart from this I wonder, what siglent will do with it´s waste amount of memory ( 200MP/250MP SDS 2K+/SDS5K) when only could used in lower timebases.

Use it for always running history mode that is very useful. Or segmented (sequential in Siglent parlance) acquisitions.

Fast realtime update rates + a circular segmented/history buffer is a great combination.

[nctnico]

Zoom mode adds one very important control that is missing when letting the scope expand around the visible window: you gain control of where the trigger is located within the full capture depth.

Basically you are trying to argue that you always should use an automatic transmission (of a car) in manual mode so you have full control without even questioning whether you actually need full control. To make the car analogy complete: you can use an automatic transmission in manual mode but you can't use a manual transmission in automatic mode. It should be obvious that a car with an automatic transmission needs less intervention from the driver to select the right gear.

[Someone]

Zoom mode adds one very important control that is missing when letting the scope expand around the visible window: you gain control of where the trigger is located within the full capture depth.

Basically you are trying to argue that you always should use an automatic transmission (of a car) in manual mode so you have full control without even questioning whether you actually need full control. To make a car analogy: you can use an automatic transmission in manual mode but you can't use a manual transmission in automatic mode.

Its much more like you so strongly prefer the manual shift pattern with reverse above 1st that you bring up "workflow" issues when anyone mentions a vehicle using anything else.

P.S. Relying on symmetric (undefined?) expansion around the window is having less control over the trigger position.... less control. Ideally a scope would have all those parameters broken out separately, but I don't know of any that do as its such an unusual use case.

[nctnico]

Perhaps you should read more careful... there are at least 3 others which use an oscilloscope the same way.

And there is no less control over the trigger position; triggering works just fine. I don't care about how much data there is exactly at either sides of the trigger point as long as it is enough. The more memory an oscilloscope can use the lower the chance that it isn't enough. Just like an automatic gearbox. As long as the car is moving the way I want it to move I don't care about the gear and engine RPM. I might want to go to manual mode to overtake quickly but after that back to full automatic.

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.

[tautech]

Or we could just start the car in gear because pressing of the clutch is just another further unnecessary operation ! 

An old fuddy duddy down the road never liked going up through the box so instead would ring the hell out of the engine in 1st so to be able to next drop it into 4th. 


Talking of gear shift patterns, ever driven a Road Ranger box where the creeper gear is directly above reverse ?

[nctnico]

Or we could just start the car in gear because pressing of the clutch is just another further unnecessary operation ! 

That is another advantage of an automatic gearbox; you don't have to press the clutch pedal. Good point!

[tautech]

Or we could just start the car in gear because pressing of the clutch is just another further unnecessary operation ! 

That is another advantage of an automatic gearbox; you don't have to press the clutch pedal. Good point!

Another thing you haven't properly thought through.
You can't start an auto in gear and once started you need to select D after pressing the foot brake and the guy that started the manual in gear is already way off down the road !

[nctnico]

Or we could just start the car in gear because pressing of the clutch is just another further unnecessary operation ! 

That is another advantage of an automatic gearbox; you don't have to press the clutch pedal. Good point!

Another thing you haven't properly thought through.
You can't start an auto in gear and once started you need to select D after pressing the foot brake and the guy that started the manual in gear is already way off down the road !

But you don't need your left foot at all. But let's stop discussing car gears.

The point is that it makes no sense trying to argue that less is somehow more. In the real world less is just less. Use your time to point Siglent to this thread and add this feature. Likely it is 3 lines of extra code. Maybe they can beat Dave to making a video showing how it doesn't work on Siglent scopes but it does work on Rigol's   

[Martin72]

Use your time to point Siglent to this thread and add this feature. Likely it is 3 lines of extra code.

If it were that simple, why not.
Having is better than needing.
But there must be a reason why they haven´t done this so far.

[tv84]

So, after all, if Siglent introduces "nico's way" all is settled?     Finally I'm starting to see the light!   

Thanks guys.

[nfmax]

Keep in mind this is *not* "zooming out"as having your scope in normal mode and just changing the timebase so you can see more of the signal, which again works on every scope. It's really about if a scope can record beyond its screen on very short timebases when the memory is set accordingly, which is only visible in a single acquisition.

Older DSOs used to behave like this. I just checked using the first DSO I ever bought with my own money - an Agilent DSO1014A (actually made by Rigol, but that's not relevant). It has a stunning 20,000 points of memory per channel (in 2-channel mode) and a 2Gsps ADC (again in 2 channel mode). Furthermore, it has the Tek-inspired memory-use display above the main window. This shows what is on the screen as a fraction of the whole memory. NewFile0.png shows the situation for X scales of 500ns/div and longer. Data is captured beyond the screen limits, and in Single or Stop mode you can increase the X scale by just less than two ranges, i.e. you get a full screen trace at 1us/div but only 8 divisions' worth at 2us/div.

If the X scale is reduced to 50ns/div you get the situation shown in NewFile1. The screen occupies a smaller fraction of the total memory, and you can now increase the X scale to 500ns/div while maintaining a full display.

On entry-level DSOs of this era and before, there is no way of varying the amount of memory used, as it was so small to begin with. Waveform update rate is limited by the acquisition engine (to 400 wfm/s), not by the number samples captured at each trigger. At higher price points, the amount of memory increased, but the ADC rate not so much. Hence, for shorter X scales (limited by the ADC sample rate), the amount of 'off-screen' memory may also be increased. At longer X scales (= 'slower timebases') the increased memory is used instead to increase the ADC sample rate. Thus short X scales allow you to zoom out more than you can zoom in, and the other way round for long X scales

It was perhaps using a scope from this era (like, e.g. the Agilent 54645) that @nctnico developed his 'zooming out' technique. It worked because, fortuitously, the X scale setting needed to show the details of the data frame was in the 'zooming out' optimised range.

The subsequent increases in ADC sample rate, and more particularly the waveform update rate wars, changed this situation again. With user-controlled memory depth, the oscilloscope designer still has to choose between using additional allocated memory to increase the ADC sample rate, thereby allowing more levels of zooming in, or to increase the off-screen capture length, allowing more levels of zooming out. Because the latter option also reduces the headline waveform update rate (because each waveform is longer), it tended to lose out. Maybe this is why @nctnico so disparages waveform update rate as a parameter - because it goes against his way of using the scope?

[EEVblog]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

[Someone]

And there is no less control over the trigger position; triggering works just fine. I don't care about how much data there is exactly at either sides of the trigger point as long as it is enough. The more memory an oscilloscope can use the lower the chance that it isn't enough.

When letting the memory depth define the size of the acquisition around the window and viewing the fast edge/information at the trigger point which you have insisted is so important to this corner case workflow, yes you have almost no control over the positioning of that extra memory.

[<------- acquisition ------- [ ---- trigger -----]------- acquisition ------->]

The trigger (while still being visible) can only be within the viewing window (not drawn to scale), roughly in the middle of the complete acquisition. If instead you use a zoomed window then the trigger can be placed anywhere within the acquisition depth while still keeping the trigger point visible:

[<-[ trigger ---------] ----------------------------- acquisition ----------->]
or
[<-------------- acquisition ----------------------------[--------- trigger]->]
etc

For someone who has gone on and on about certain scopes having less memory under different modes etc, potentially throwing away half your memory and claiming its completely under control is hypocrisy.

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.

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.

Perhaps you should read more careful... there are at least 3 others which use an oscilloscope the same way.

Enjoy your confirmation bias, perhaps you'd find solace with the flat earthers: https://forum.tfes.org

[nfmax]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

But that only works because when you press Stop, the Keysight scopes make one last acquisition using the maximum available memory (providing a trigger arrives in time). It's a neat trick, and it does work.

[KE5FX]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

Unless they patented it.

This kind of thing is the USPTO's bread and butter.  "We claim: 1. A digital oscilloscope that doesn't suck." 

[EEVblog]

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:
(Attachment Link)

That sounds right. It's doing just the screen worth in Normal or Auto mode because it needs the fastest update rate possible. There is no point capturing continuous updating data outside the screen if the user can't see it.
So yes, doesn't surprise me that this only works in STOP or Single mode, because these modes are, practically by their usage definition, analysis modes were you may want to expand the timebase to view that extra data. So when the scope has been instructed perform STOP or Single mode it makes sense to then capture the entire available memory length regardless of what the user has set, because update rate no longer has any relevance.

Come to think of it this way now, there should be absolutely no reason why the likes of Siglent could not implement this easily with a firmware update. The likely reason they haven't is because they just haven't thought of it before.

To summarise, I think STOP mode or Single Mode should ultislise all available hardware memory regardless of current memory setting and at the fastest sample rate. This is clearly what Keysight have opted to do.
And perhaps that's a better description of this issue, "Capture memory depth in STOP/Single mode".

[Someone]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

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.

All that extra memory around the aquisition window kills waveform update rates (a tradeoff which is completely acceptable for some uses). Here is the plot from a Tek DPO4000:

Extending the acquisition buffer each side of the trigger outside the window on the screen is shown with dotted lines toward the right. It knocks orders of magnitude off the update rate.

Although there are more intelligent memory management options, scopes are rather simple/dumb. They won't redraw/paint another trigger until the full memory depth is filled. So at 5GS/s and 10M memory depth, even a perfect zero overhead, instant trigger will only run 500 updates/s.

[nctnico]

Because the latter option also reduces the headline waveform update rate (because each waveform is longer), it tended to lose out. Maybe this is why @nctnico so disparages waveform update rate as a parameter - because it goes against his way of using the scope?

No. In some case having lots of waveforms/s is useful; setting the memory length shorter either manually or automatically gets you the highest waveform update. You can have the best of everything no matter what.

My beef with waveforms/s is that it is a number used purely for marketing wankery because the maximum number is only achieved in very specific use cases which don't represent actual use cases. The number of waveforms/s is highest with the least number of points, where the trigger dead-time versus acquisition time is at an optimum and (usually) in dot mode only. This means that you'll be looking at a screen with a whole bunch of dots instead of a signal in some cases.

[EEVblog]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

But that only works because when you press Stop, the Keysight scopes make one last acquisition using the maximum available memory (providing a trigger arrives in time). It's a neat trick, and it does work.

Ah, you just came to the same conclusion I did in my post above!
That's exactly what Keysight have elected to do, and I think it's smart.

[2N3055]

Or we could just start the car in gear because pressing of the clutch is just another further unnecessary operation ! 

That is another advantage of an automatic gearbox; you don't have to press the clutch pedal. Good point!

Another thing you haven't properly thought through.
You can't start an auto in gear and once started you need to select D after pressing the foot brake and the guy that started the manual in gear is already way off down the road !

But you don't need your left foot at all. But let's stop discussing car gears.

The point is that it makes no sense trying to argue that less is somehow more. In the real world less is just less. Use your time to point Siglent to this thread and add this feature. Likely it is 3 lines of extra code. Maybe they can beat Dave to making a video showing how it doesn't work on Siglent scopes but it does work on Rigol's   

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. What you are proposing is good for events that are sparse, and where things happen so slow, you actually have time to literally see something weird on screen, mentally have time to recognize it as weird and make a decisions to stop, and then have time for you to move hand and manually stop acquisitions.
Segmented acquisitions are literally invented for those kinds of events... So to work on that kind problems, you use segmented mode. On LeCroy, Siglent, Pic and some R&S scopes (I know of those if there are more please let me know)you have history mode, that is sort of always running segmented mode, with no penalties to normal running.

For that kind of events, I put Pico to slow timescale with deep memory so I keep high acquisition rate, and capture 100 ms at a time, and keep getting those captures to memory, 100s of them if needed.
Then I use built in search to scour trough captures..I also use DeepMeasure to search for analog anomalies across all of those (edges, P-P, pulse widths). I export DeepMeasure to Excel, and make statistics and histograms of all those prameters, to catch outliers and get a feeling of distribution... Or I put my 3000T or Pico to segmented mode and just capture those bursts of data, ignoring "eons" of pause in between. Pico 3406D has retrigger time in segmented mode even faster that 3000T (Trigger rearm time   < 0.7 µs at 1 GS/s sampling rate, )
When looking at normal scope stuff, I like that my 3000T uses auto memory management, so it can reach up to 1.2 MHz retrigger rate. It makes it feel like "real scope".

[nfmax]

And I don't get how fast waveform updates suddenly become relevant in this thread; capturing beyond the screen has no downsides.

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.

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.

You should use Single mode in that case

[tautech]

Apart from this I wonder, what siglent will do with it´s waste amount of memory ( 200MP/250MP SDS 2K+/SDS5K) when only could used in lower timebases.

It's YOUR memory to know how to use wisely......again yours !
Lower timebases, bah humbug. 

Study the dot mode screenshot below.....left at that timebase setting for understanding but 1 dot/div (1 memory point) is available at 200ps/div.
Total of 500 MPts with 2 channels on alternative ADC's.