Products > Test Equipment
Analog vs digital X-Y mode
pdenisowski:
--- Quote from: CRTbrain on August 27, 2024, 03:05:52 pm ---digital scope do poorly with XY because they inherently have slow update rate. R&S has the fastest update rate with MXO4 and MXO5....but they don't yet support XY mode...and maybe their XY mode, when released, will be in SW or maybe in HW. All digital scopes so far have XY done in SW.
--- End quote ---
I guess you'll just have to wait and see :)
wolfy007:
Digital scopes dont do so bad these days, even some of the cheap ones, below are a few examples from various age groups and price range using the Dutchtronix clock (my favourite XY test), all of which show the clock fairly smoothly once you get the setting right.
KungFuJosh:
I couldn't say how legit, but the Batronix demo video for the Magnova oscilloscope had what looked like X-Y mode that impressed me more than any other modern scope so far.
Phil1977:
Does anyone know how much dead time the current digital scopes have in xy mode?
AFAIK modern xy mode is a spin-off of the digital phosphor technology. Many digital scopes even keep the trigger activated in XY-mode. This means, each time the trigger is activated, a snapshot of the signal on X and Y is taken and summarized to the display matrix.
But this also means that the time between the snapshots is just plotted to the screen.
In the end we have (at least) three main differences comparing analogue to digital:
- Analogue is without any dead time. XY-mode does not even need an electron beam return blank.
- Analogue has no latency or display update rate
- Analogue has no quantisation effects reducing the available resolution
Is there any modern digital scope that really addresses all these issues? At least for lower bandwidths I could imagine a continuos, triggerless data acquisition like in roll-mode. Display update rate is a matter of computing power and the relevance of quantisation is a matter of available memory - so very theoretically it may be possible, but did anyone do it?
MathWizard:
--- Quote from: David Hess on March 22, 2018, 03:16:05 pm ---
--- Quote from: Tom45 on March 22, 2018, 04:03:32 am ---So why do digital scopes do so poorly in X-Y mode?
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DSOs have six problems with X-Y mode:
1. Non-index graded displays cannot be anti-aliased and most DSOs with index graded displays do not anti-alias anyway or anti-alias poorly; this becomes an additional source of quantization noise. Note that the analog examples above show a raster displayed on a vector display device producing further aliasing on the DSOs. A true vector implementation would look better on both types of oscilloscopes.
2. DSOs suffer from quantization noise from the digitizer which is usually handled poorly in X-Y mode. High resolution mode should solve this. Average acquisition mode should also solve this unless it lowers the update rate.
3. Most DSOs produce display updates by batching record length groups of samples. If the vector generation time does not fill the record length evenly, then the display updates either miss or overlap sections. "Phosphor" type DSOs still update the display in batches determined by the number of samples between display updates.
4. DSO display refresh and update rate is orders of magnitude slower than the continuous update rate of an analog oscilloscope. This should not matter above about 60 Hz but combined with 3 above it becomes a problem.
5. Almost all DSO displays have a much lower resolution per area than an analog CRT. Many old CRT DSOs operated at 254dpi (100dpc) and could produce a pretty good vector display in X-Y mode except for the record length and update rate issues described above despite lacking anti-aliasing.
6. Most DSOs do not support a Z-axis (intensity) input so all of the vectors run together. The Rigol example above shows this.
These issues with DSO XY mode could be fixed to produce a display limited only by the display device itself but it is hardly a high priority.
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So what could happen if you took some scope, and tried to get it working with a nice gaming PC. Surely if it's possible, someone with nothing better to do, has tried it.
So with say a 1440p, 144Hz monitor, and some top of the line CPU and GPU ?? How good of an X-Y scope or regular scope could you make then ??
What about years ago, when all CRT scopes had tiny screens, did people try to hack them together with nice big CRT TV's ??
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