Multiple traces after STOP button is pressed - Page 1
Forum section: electronics / testgear

author: Circlotron
author_rank: Super Contributor
timestamp: August 16, 2017, 12:54:37 pm
content: So I'm watching a trace that is a bit jittery so it varies a bit from one trace to the next. Then I press the stop button and i would expect to see the last trace left on the screen, but in fact I see the last several traces. See video. What is going on here??? Rigol DS2072.https://youtu.be/NpWri9LCq7w

author: rf-loop
author_rank: Super Contributor
timestamp: August 16, 2017, 01:19:57 pm
content: Quote from: Circlotron on August 16, 2017, 12:54:37 pmIt works just af it is designed and made.Think if oscilloscope capture example 10000 waveforms/sScreen is refreshed example 25 times in second.One screen can contain last 400 acquisitions.Today scopes are very different if compare to old school museum digital oscilloscopes what do acquisition and after then put it to dislpay and then nexext acq. and then this new is writed to display and old flushed out.Todays DPO type scopes works bit different.Some oscilloscopes have selection for force oscilloscope to do this sequential acg...display...acq....display... as old slow digital scopes.Example in Siglent there is default fast acquisition but user can also force it to slow. In this Slow mode there is only one acquisition for every TFT frame refresh. I am not sure if this can find also in Rigol.But you can do it other way if you want only one last acquisition.Use Sinle mode for triggering. when it trig it acquire and stop. Just one is displayed.Other wayUse normal Normal mode (or Auto if not much experience with settings) for triggering and then adjust Trigger holdoff time to enough long so that it can trig only once for every TFT refresh. In this case when you stop scope there is one last acquisition visible.

author: Circlotron
author_rank: Super Contributor
timestamp: August 16, 2017, 01:32:40 pm
content: Quote from: rf-loop on August 16, 2017, 01:19:57 pmSingle mode works okay. I was just wondering why it would display several traces when normal mode gets stopped.I'd be interested to see if the Rigol scope has a "slow" mode.

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2017, 01:36:38 pm
content: Quote from: Circlotron on August 16, 2017, 01:32:40 pmThere's probably an option to enable/disable this display. Look in the waveform recording menu, etc.

author: Berni
author_rank: Super Contributor
timestamp: August 16, 2017, 02:16:42 pm
content: It depends who you ask, some will say this is the right way to do it.I come from a history of using Agilent scopes. There the stop button causes it to show a single waveform fro the last trigger so i generally expect stop buttons to work this way. But some scopes have a different idea of the stop button where it freezes the current image on the screen. So if there was a lot going on and there ware multiple triggers within one display refresh then it stops with multiple waveforms on screen.We have one of those portable Micsig touchscreen scopes at work and it also has this stop button behavior that captures multiple waveforms, on that its made worse by it having a really long display persistence timeout so that on slow triggering signals there might be over a second worth of old persistent waveforms on the screen. The stop button behavior kept bothering me.

author: borjam
author_rank: Unknown
timestamp: August 16, 2017, 02:28:08 pm
content: Quote from: Fungus on August 16, 2017, 01:36:38 pmOtherwise, just reduce storage memory to the minimum.

author: borjam
author_rank: Unknown
timestamp: August 16, 2017, 02:54:23 pm
content: Quote from: rf-loop on August 16, 2017, 01:19:57 pmAnd I was wondering what that "slow/fast mode" option was doing!This kind of information should be in the user manual

author: rf-loop
author_rank: Super Contributor
timestamp: August 16, 2017, 09:42:45 pm
content: Quote from: Berni on August 16, 2017, 02:16:42 pmYes. These all what we can see in display after stop is information about signal. Why flush information to garbage as default. I have used this kind of scope and all times it make me angry, why it flush out interesting data and show only last one. It must display to user all possible what it have.It can do more clever. Stop, scope show all information what it have (freeze display with tens or hundreds or even thousends of stacked last acquisiotions giving also "third dimension" (Z) about signal.) After then user can touch it and only last acquisition is displayed. This is idea how example Siglent works or should work.But after then there is also more. If user is interested about acquisitions before stop he/she can look these. Depending memory and time settings up to 80000 previously trigged acquisitions. These can find in history fifo. Exept if he have <censored>. User can play this history buffer or just select every single acquistion (limiting of course how much it can store) and do cursor and automatic measurements, use FFT or do window zoom or whole screen zoom because in history buffer all is raw sample data, not imagepixelmap traces.

author: Circlotron
author_rank: Super Contributor
timestamp: August 16, 2017, 11:00:41 pm
content: On my Rigol after you press the stop button if you change the time/div up and down a notch it then displays a single clear trace.

author: tooki
author_rank: Super Contributor
timestamp: August 19, 2017, 11:25:40 am
content: Also, try reducing the display persistence to the minimum.