Hi rf-loop!
Thanks for the quick reply and providing your data! I totally understand that these may be rough measurements, and I won't take anything I see as gospel. That being said, this is a great starting point and certainly very informative. While looking this over, I did have a couple questions about this information.
1)
First, why do some rows have a single measurement for the 4 columns, and others have 4 measurements? If there's a single measurement, does that mean the update rate was identical for all 4 conditions? Or is that just a single data point and you haven't had a chance to collect all the data for some of the "t/div" rows?
2)
Second, why did you decide to change the frequency of the test signal as your timebase changed? Did you find it affected the update rate? I wouldn't expect that to impact the waveform update rate, so I'm surprised to see that was varied.
3)
I don't think it should matter one way or the other, but do you remember if the trigger mode was set to "normal" or "auto" when you took this data?
4)
Lastly, I'm surprised to see the update rate was affected by the interpolation mode when the scope was displaying dots. I would have guessed that, since no interpolation is occurring, it wouldn't matter what that setting is. I wonder what the code is doing behind the scenes...
1.
Rows where is one value for 2 or 4 conditions, you can see there is combined columns. It means same value for these conditions. ( or difference is very insignificant)
2.
In some cases signal affect to speed (more or less). If I want look 10MHz signal usually I do not look it using 1ms/div so I have selected even somehow usable freq for t/div. Test signal is not selected for best possible speed. Many things affect wfm/s speed... including signal figure. It can somehow understand if think how intensity or color gradation is produced. It need some brute force. Also there is somehow two separate things in this process. Inside one wfm intensity some gradation and then sequential overlaid wfms intensity gradation. Think if there is 100k points data for one single capture (aka wfm). On the screen there is 1000 columns for this data. Every 100 sample need plot to one column and next 100 samples to next column... now if samples value is same they need plot to same "pixel"... (Siglent do not decimate data what is mapped for display)
Then come next waveform what is plotted to these same places on display and now... roughly said... how much these data collide on screen more intensity.
(difficult to explain using foreign language)
And also, this all happen independent of display mode and what is interpolation)
If display refresh rate is 30Hz and we have 120kwfm/s speed it mean 3600 sequential acquisition data is mapped to one display frame with intensity gradation. And more, in final when it produce this image for display it still keep also all these acquisitions in memory with full data. (In history buffer)
3.
Trigger is Edge, Rising. With these speeds it do not matter if trig is normal or auto because there is not so long pause between trigger even in signal that Auto trig start generate trig.
4.
It depends...
But think about it so that in every case signal displayed on screen need be on the screen so that trigger position is perfect. If sampling interval is example 1ns (1GSa/s) and we use 1ns/div Horizontal scale. Still if we do not draw line to display still we need somewhere fine interpolate trigger position between real sample data points... Still you can see that also using dots mode trigger time axis position on screen is quite perfect. Position is based to interpolation between individual samples. 1ns is long time... I do not remember what is fine positioning interval.. but when data sheet tell about trigger: Jitter CH1~CH4:
<10 ps rms. It means that fine interpolation between real samples need do very finely divided. I don't want to speculate or say anything about which part belongs deep in the "digital trigger engine" area between the ADC and memory and which is post-processed display positioning. Siglent will publish more in-depth information about the operating principle if it wishes to do so. Now there is no such public information.
But in every case, this process also need some processing brute forge and it can not happen without consuming time.
Yes, this would be a nice place for a dedicated ASIC, and ping pong acq. principle for speed but now there isn't... Buyers don't release enough money from their pockets for this.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
After around 1 week is will try quick check if there is any major changes in table (latest FW latest HW)
If no major differences then new revised table later after suitable time for it. (Also it need note that this wfm/s speed
The importance of this speed should also not be exaggerated (still it is nonsense but no need over estimate). A modern oscilloscope has many other features that can reduce the importance of this speed. Very few people look for rare random distractions by looking at a screen. A person can do something wiser and entrust such work to a modern oscilloscope. It's worth remembering that Keysight, one of the wfm/s hypemen, is married to their old ASIC chip system, where the triggering is handled by an ancient analog sidepath trigger system, which is still pretty good at it. However, it does somewhat limit the triggers that can be harnessed for that bug hunt. In addition, oscilloscopes do many other things. I use it to analyze the signal in many ways. And many analyzes do not require a million wfm/s. Sometimes when you read Kysight wfm/s hyping advertisements, it feels like they have nothing else to do.