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A newbie needs some help with my first DSO
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Fungus:

--- Quote from: awakephd on June 04, 2024, 12:16:14 am ---FWIW, I would hate for anyone to get too excited about what I might or might not have expected. I was expecting the waveform capture to start at the trigger point, so discovering that the scope captures all sorts of pre-trigger data was a big surprise. A very welcome, big surprise! :)

--- End quote ---

The trigger point is in the center of the buffer.
tautech:

--- Quote from: Fungus on June 04, 2024, 01:02:07 am ---
--- Quote from: awakephd on June 04, 2024, 12:16:14 am ---FWIW, I would hate for anyone to get too excited about what I might or might not have expected. I was expecting the waveform capture to start at the trigger point, so discovering that the scope captures all sorts of pre-trigger data was a big surprise. A very welcome, big surprise! :)

--- End quote ---

The trigger point is in the center of the buffer.

--- End quote ---
:-DD

And where if you place H Pos on the first graticule ?
Fungus:

--- Quote from: Someone on June 04, 2024, 12:55:05 am ---So, it is model specific and people need to learn how their specific unit works. Industry standard my foot.

--- End quote ---

I don't have mine any more but that's not how I remember my DS1054Z working.

Anybody still have theirs...?

The Siglent refuses to capture outside the screen even when you set the memory depth manually to something much larger than the display.
Someone:

--- Quote from: Fungus on June 04, 2024, 01:23:00 am ---
--- Quote from: Someone on June 04, 2024, 12:55:05 am ---So, it is model specific and people need to learn how their specific unit works. Industry standard my foot.

--- End quote ---
The Siglent refuses to capture outside the screen even when you set the memory depth manually to something much larger than the display.
--- End quote ---
So, lots of other scopes do this too. You just set the window to your preferred length and position then leave the zoom window open on the bit you want to see.

At this point you're arguing about the difference between the presented Rigol example with its large boarders, vs the Siglent which takes up around 1/3 of the screen.

So it's back to you taking preference to not see any content of the long capture unless you stop, vs others happy to see some detail of the long capture. But instead of just saying that its some convoluted mess about how CANT DO THING.

Why get emotional about it? Add personification to a scope? "The Siglent refuses"  :-DD

Should I bomb any mention of a Rigol scope with your example of a scope that cant keep the memory depth to only the visible screen? It cant do some things other scoopes can, but its not some major issues that greatly limits the use of the scope.
2N3055:

--- Quote from: Fungus on June 04, 2024, 01:23:00 am ---
--- Quote from: Someone on June 04, 2024, 12:55:05 am ---So, it is model specific and people need to learn how their specific unit works. Industry standard my foot.

--- End quote ---

I don't have mine any more but that's not how I remember my DS1054Z working.

Anybody still have theirs...?

The Siglent refuses to capture outside the screen even when you set the memory depth manually to something much larger than the display.

--- End quote ---

Why are you claiming things that are not true?
Where did you get this information?

If you have Siglent scope that has manual memory control, it captures it same as R&S or any other scope that has it. You get trigger, and it captures exact amount you set it for.

But that beside the point, claiming that it is a good thing that scope always captures fixed amount of data instead of only what you need is simply laughable.

Old digital scopes had manual fixed memory length and you always had to twiddle manually and remember and think what you set and what is optimal.
Always long memory decreases number of triggers/s because it always captures lots of data. It slows down a scope, measurements, everything.
But OTOH, short memory forces scope to drop sampling rate.
And it frustrated people to no end. Manual memory mode is one of the main reason why people hated early DSO. If you had it on short memory it would alias all the time. If you set it to long memory it was SLOOW... Only few triggers per second... Wonder why...hmmm...

So after some time, scopes started coming with Auto memory management mode.
That one would automatically set memory length as you go through time base. Shorter memory on short time bases, longer as you go to longer timebases to keep sampling rate up (to avoid aliasing). As scope would get to max memory, then sample rate would eventually be dropped.
And everybody liked it because they were fed up with constantly twiddling memory settings.

This Auto mode exist on Siglent and Rigol. And Tek. And R&S and Micsig.
And manual mode works exactly the same on those too. Some Siglents have, some don't have manual memory mode. Nobody uses it anyways. It is a pain for actual use..

Difference (that confuses people) is that some scopes, when automatically set memory length, will have only few fixed memory lengths, and some will have an exact length for each timebase individually.

For instance Keysight 3000T. It has Auto memory mode. People keep repeating "it captures outside the screen!".  It actually does not....
It uses a a trick when you stop the scope.
Take for an example a burst of data happening every 5 seconds.
You set it in Run mode, Normal trigger mode. It waits for signal.
Burst comes in. Capture.
You press Stop.
If you change timebase now, there is nothing outside the screen. WHAT?
BBButt Dave said there is....
Well. Dave is (partially?) wrong. It is not his fault (well he could have researched better before going on record..) but he was tricked.

See, MSOX3000T (and all other Megazooms IV) captures only what is on the screen in Run mode. But when you press Stop, it quickly reconfigures acquisition engine, and then initiates another trigger and captures ±200µ around the trigger. Unless you press Single in which case it will capture ±400µ around the trigger. That deletes last capture (one that you were looking into that prompted you to press Stop). If you are at 20µs/div or shorter. Unless you are at slower timebase in which case it doesn't. Or maybe. Or it does something else.

So it is a crapshoot. You might get something, or not, or maybe. If you do, it is going to be some random time. And only at fast timebases, 20µs/div and faster. To a serious person, that is not something to rely on. And the capture on the screen is not the one that you were looking at when you pressed Stop. That one was deleted and you get a different new one. Unless it times out (because signal is rare) in which case you get only what was on screen. So basically it is a lottery..

Only sure thing that will guarantee you will capture x amount of time around the trigger is to set the scope to do explicitly. With setting pretrigger time and post trigger time. Simplest, quickest and most intuitive way is to set it that scope shows the interval in question on the screen. It is simple. Like on analog scope. If it is not on the screen, you are not looking at it and you cannot see it.
It works on any and every scope including old CRT ones. And on digital scope, if you Stop it at that moment, you can than magnify portion of detail, by using timebase, Zoom, multiple windows or whatever scope in question supports and whatever is useful to you.


Everything else is mental acrobatics, or some special (forced?) corner case.
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