All,
I hate that this is already devolving into arguments. That will make it harder for the newbie to sort the wheat from the chaff (it lowers the s/n ratio, to use an electronics metaphor).
I understand that everyone is passionate about their preferred brand, but from the perspective of a newbie, I don't and can't have any opinion on which is the "right" or "best" way to do something; if one scope does it this way and another does it that way, that is, ATM, just an "aha" for me. Eventually I may develop a preference, and perhaps, in time, I too will be converted into righteous indignation when anyone attempts to suggest it should be done some other way. For now, I'm just trying to figure the bloody thing out! All that to say, if it is possible, if you would be willing, it would help me tremendously to state things more in terms of "this is how brand x does it" rather than "brand x is stupid and defective for doing it that way."
The link to Dave's video was actually very helpful for me in making sense of what memory depth is. I confess that i was assuming it would work more like the Keysight, which is part of why I was having trouble understanding - I hit "stop," but there was no data past the end of the screen. I think I am now understanding that, for the Siglent and a few others, what is captured is only what fits on the screen at a given moment - thus, one must zoom out, capture, then zoom in to see detail. Right? Maybe?
To take a practical example, if I am trying to decode some messages on an SPI bus, here is what I think I am understanding: On the Siglent, I will need to show "all" of the messages on the screen to capture them - even though at that point they will be so squished together than I can't discern the content of any of the messages. Then, once capture, I can zoom in and scroll through to see the actual content of the messages. Have I got it right?
One more possibly related question. I feel rather dumb for asking this, but ... I think I have just begun to realize that the "trigger point" of the waveform on the screen is actually in the center of the screen (by default), meaning that the scope is showing me events that happened
before the trigger. Is that correct? Unless I have completely forgotten what I have done in the past with my old analog Tektronix, this is very different behavior, as the analog scope starts the sweep at the trigger, meaning that anything prior to the trigger simply cannot be shown. Clearly this is a huge advantage for the DSO! And if I understand correctly, I can adjust the trigger point left and right, so that I see less of what happened prior to the trigger and more after, or vice versa.
I will greatly appreciate your (hopefully gentle) correction and redirection if I have muddled up any of the above. I am learning! And I am working my way through the manual! Now I just need more time ... irritating that work is getting in the way of pursuing my hobby, but there it is ...