Honestly, the point mode from Siglent does not show anything useful. I could not find a way how to show only points …
Well, let’s examine that a bit.
I don’t have a fancy pulser, but maybe a well defined pulse from a pulse generator, even if it’s a little bit slower at 500 ps rise time, might be even more appropriate for characterizing a moderate bandwidth oscilloscope.
So the test pulse has a repetition rate of 10 MHz, 500 ps transition times and is 1 ns wide.
The first screenshot has been taken with Sinc reconstruction, vector display mode, color grading and 10 s persistence.
SDS2354X_Plus_PR_10MHz_500ps_vect_CG
What do we see ? There are not any signs of aliasing. There is no pre-shot. There is a very moderate low frequency ringing at the end of the falling edge. The signal is rock stable, as the thin trace and the low standard deviation in the time measurements show. The amplitude measurement on the other hand cannot be very stable, as this fast pulse doesn’t have a well defined “roof”
Now let’s try the same thing in dots mode, which is claimed to “not show anything useful”…
SDS2354X_Plus_PR_10MHz_500ps_dot_IG
As can be seen, I’ve used the standard intensity grading this time, as color grading and not even persistence show anything spectacular at all. I wish every feature in any T&M gear were as “useless” as dots mode in a SDS2000X Plus.
Of course, for dots mode to yield nice results as in this picture, we need to have the DSO set to “fast acquisition” and keep it in Run mode, so that SARI (Sequential Acquisitions Random Interleaving) can do its job. With persistence enabled, we can even switch to Stop mode and still have a contiguous trace. A single shot acquisition on the other hand will always allow the closer inspection of the individual samples of a single acquisition:
SDS2354X_Plus_PR_10MHz_500ps_dot_IG_Single
Yes, we don’t see a lot in this picture, but it’s always nice to have the option to see the raw basis the instrument is working on.
Of course we can look at the history any time we like and there we can look at the individual records (up to 80000 at fast time bases like this) and try dots mode to show the true samples only, vector mode, where we can select between x-interpolation and Sinc reconstruction, as well as even persistence, which will collect display data as we browse through the history or play it back at any arbitrary speed.
and the linear extrapolation looks silly. I can try with HP but later. Attached is SDA6020 if it helps.
x-interpolation can avoid Gibbs ears in some situation, but is usually just an obsolete leftover from the old days of digital oscilloscopes, when there wasn’t enough processing power to run a true reconstruction (Sinc aka sin(x)/x). It is evident, that the sample rate should be about ten times the input (or signal) bandwidth for linear interpolation to work.
In our particular case, linear (x) interpolation isn’t terribly useful, yet it gives a nice demonstration of the intensity grading:
SDS2354X_Plus_PR_10MHz_500ps_vect_IG_Lin