Workaround from Keysight is dangerous trick. If you set Normal trigger mode, wait for a sparse trigger, you get several, you see on the screen something interesting and press stop two things might happen: if there is a trigger within few hundreds milliseconds it will destroy capture from the screen, and get another long capture. Different from the one because of which you stopped the scope. Second option is that if you don't get a new triggerable event in that period, then it will stop and show you your screen. It will not have anything but on the screen in memory. So see, that Keysight trick doesn't work at all, and it's only purpose is to pretend it does...
Ha-ha! So you are telling us that you:
(1) watch the screen of an oscilloscope capable of displaying >100,000 waveforms/second (and plotting the result on screen at a rate of at least 30Hz);
(2) notice a single rare event;
(3) press the STOP button to freeze the said rare event and inspect what’s outside of the curve plotted on screen;
(4) get a wave on the screen you can, indeed, zoom out BUT doesn’t show the rare event anymore?
(5) … and then you blame Keysight’s “dangerous” work-around that assumes that your reaction time is slower than the speed of light, so any non-naïve user would not do what you describe in the first place?
Bad example, doesn’t support your point…
You understood it completely wrong. Did you read it at all or was I so bad at explaining?
THIS is exactly what Nico does and people call zoom out.. not me.
I was writing it out to illustrate how ridiculous it is..
It absolutely IS my point.
scenario that is proposed (not by me):
1. You are not plotting at 30 Hz because scope is set to max memory and you cannot get more than 5 triggers per second.
2. events are spaced every few seconds.. there is enough time to look at the screen and notice something interesting.
3. you quickly press stop. Now you have full buffer of 200ms of stuff around that trigger to investigate at will.
This is Nico's scenario and it makes sense to me. But this is not Keysight but a scope that has full manual memory mode and 100 times (literally) more memory.
I was explaining how Keysight DOES not capture outside screen but only pretends it does.
When scope is in Normal trigger mode screen is frozen between trigger events and shows capture from last trigger event.
Let's say there is burst every 1 seconds, but there is randomness in period so sometimes it shoot two bursts close...
So you're looking at the screen and you see some anomaly.
You press stop. here there are two possible outcomes:
1. there is no another burst within some short timeout period. In which case there IS NOTHING outside the screen.
2. there is another burst from DUT that invokes additional trigger event (in short time
after you pressed STOP), which gets captured in full memory and you can see that on the screen. Screen that was on when you wanted to investigate is gone and you are looking at something else...
Is this better explanation.. ?