Trying out posting in the Oscilloscope Zoom Out Quirk thread with quoted messages from a different thread, so as to retain all context while posting in the proper thread ...
There is no free lunch. There is no data being captured outside set time. It is only that you can set time by obscure mental calculation (flying blind and calculating sample rate/ manual memory length ratio) or by simply setting proper time base in a first place...
You keep on repeating this but it isn't true. In fact for many of the measurements I do, I don't even care about time/div setting. And in some cases (like verifying protocol bitrates which can be off by a factor 100) I don't even know which time/div setting I'd need to use to get the signal on screen.
Well, if you don't care about the timebase setting then that means you can set it to whatever setting gets you the maximum amount of time on the screen while retaining the scope's full sample rate (or to capture however much time you like), right? This means that, for these use cases at least, the Siglent approach will work just fine for you. What, then, is the problem?
The deep memory simply makes sure there is always enough data. I make a measurement and twist the time/div knob until there is a visible signal. Then I use a measurement and / or cursors to tell me what I want to know. There is zero mental calculation and zero preparation.
OK, but you have to set the timebase to
something. How do you set it on your scope so as to get the maximum capture depth while also retaining the sample rate you want?
On the Siglent, this is directly visible, especially on the 2k+ and up. The little timebase box at the bottom of the screen shows the sample rate, the memory depth, and the timebase. This makes it trivial to set the scope up to capture into the entirety of available memory while retaining the maximum sample rate.
For the scopes you use, does it
always capture into
all available memory irrespective of your timebase? My Instek does, except that I have to always define the amount of available memory (in points), and if I define it to be less than the amount the scope has, then it will simply leave the rest unused, while the Siglent will use the remainder for remembering prior captures.
But we have been around this before. It is like the eternal discussion about automatic / stick shift in cars. The thing is a good DSO offers both so everyone can be happy.
I completely agree, and I'm happy that Siglent has seen the light on this. But how many offer
both "what you see is all you get"
and "a capture always uses all the available memory", selectable by the user?
Again: suggesting to use the zoom window is just stupid. Especially on the lower end scopes, the zoom window takes away a significant portation of the already small screen. It doesn't help improve the useability especially if you have a bunch of traces and protocol decoding enabled.
That's true on the lower end scopes. The higher end scopes have enough real estate and resolution that zoom mode is very functional, even with protocol decoding and multiple traces. If you're stopping the scope (either because you used single capture or because you manually stopped the scope), then you can use the full screen to move around and zoom in and out within the capture as you please.
I will say this: for single capture mode, it really should use all the available memory
always. This is because the history buys you nothing, since each time you press the "single" button it'll clear the history, so the scope may as well use all the memory for the one capture you're performing. This is the one exception that Siglent should have made to the "what you see is all you get" behavior from the start. Either that, or it should remember prior captures as long as the capture parameters (timebase, trigger settings, etc.) remain the same.
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