Siglent SDS1202X-E roll mode not continuous? - Page 1
Forum section: electronics / testgear

author: JBeale
author_rank: Frequent Contributor
timestamp: August 30, 2018, 10:45:54 pm
content: Just got a Siglent SDS 1202X-E which sports a lot more measurement options than my old Tek TDS210. Happy to find that the fan is relatively quiet. This model reports Software Version 7.1.3.17R1I expected that at slow sweep settings, the "roll mode" would show the waveform continually scrolling to the left for as long as the mode is enabled, like an old-school stripchart recorder, but that is not what happens. As soon as the end of the trace has scrolled across the screen to touch the left hand edge, everything instantly goes blank. It then restarts fresh from the right hand edge. Is it intended to work this way? I can't imagine why this one-screen-at-a-time kind of a "roll" mode would ever be more useful than one where the data rolls continually and you can always see and refer to a full screen of the older data. It seems like bug to me. I thought it might be related to the memory depth setting, but it happens regardless of that setting.Is there any setting which allows a continuous scroll without the reset after each full screen?Other scopes I have used, like the TDS210 do not scroll the whole screen on slow sweep, but they do update the trace live as it moves across, like a CRT analog storage scope would, only erasing the oldest data pixel-by-pixel as new data comes in. That's a lot more useful in my opinion since you can always see the signal "now". Siglent doesn't offer that mode either; if you turn off "roll" then you have to wait one full sweep (for example 14 seconds, at 1 sec/div) before seeing any data at all.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 30, 2018, 11:11:51 pm
content: Roll mode does not enable automatically at slow sweep speeds, you have to specifically enable it by hitting the Roll button. And it automatically comes out of roll mode once you set the horizontal to faster than 20ms/div. If you don't see the Roll button lit up (and Roll in the top left corner), then it's not in roll mode.

author: JBeale
author_rank: Frequent Contributor
timestamp: August 30, 2018, 11:13:59 pm
content: I am pressing the "Roll" button and it does light up. It behaves as I described, as shown in the video below. Does your scope behave differently?

author: tautech
author_rank: Super Contributor
timestamp: August 30, 2018, 11:28:40 pm
content: There's two different Roll Mode modes.If the timebase is set to 50ms/div the Roll mode button will illuminate and the displayed 'live' waveform starts filling the display from the right. This is auto Roll mode.Dedicated Roll Mode is different in that it clears memory buffers and then stores the complete sweep before updating the display.Hope that helps with understanding.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 30, 2018, 11:46:22 pm
content: I'm not entirely sure thats whats going on here. Fixing to head out so don't have time to continue testing, but I'm able to get the same results as OP, but only when vertical sensitivity is set to 5mv/div or less (x1). Anything more than that and it seems to be in 'normal' roll mode, with a continuously updating waveform. If you look at OPs video, it doesn't seem to quite line up with either mode you are suggesting. The waveform starts from the right of the screen like you would expect in roll mode, moves to the left of the screen, but at some point it resets and starts over. Its live drawing it the whole time, but blanks and starts redrawing from the right.It's certainly possible I'm misunderstanding (admittedly rarely had a use for roll mode, so not much experience with it) what I'm seeing, but I agree with OP that that doesn't appear to be the correct behavior.Edit: Meant to mention, I have an unliberated SDS1104X-E with the latest firmware and OS. Sorry, don't have time to find the actual version numbers.

author: JBeale
author_rank: Frequent Contributor
timestamp: August 31, 2018, 12:07:23 am
content: Thanks for having a look at your scope. Maybe this behavior is specific to the 1202X-E model, but for me when the "Roll" button is lit up, it works the same way as shown in the video, regardless of the vertical setting. I showed it at a higher gain, but it also works the same through the full range, all the way to 10V/div at 1x.EDIT:I see now that my scope CAN do a continuous roll with the right settings. There is an interaction with the trigger setting and the trigger mode. If you are in "normal" trigger mode AND the signal passes through the trigger point, it will blank the screen and restart once the trace reaches the left-hand edge of the screen. If the signal does not pass through the trigger point (as it might be with lower vertical gain and/or less noise) then it will not restart. However if you are in "auto" or "single" trigger mode then the roll works continually as expected, without blanking the screen unless you change some other setting. I guess I was expecting "of course" the scope would automatically ignore the sweep trigger when in Roll mode, but apparently not.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 31, 2018, 03:46:57 am
content: I was thinking it might be something like that after initially seeing your video, but after more playing around with my scope I don't think thats the case. Plus, trigger level and triggering really shouldn't come in to play for roll mode. In this video I am feeding a 10mV signal into the scope, trigger level is at less that 1mV. For the first 30 seconds I've got the scope set to 2mV/div. You can see the reset happen at 10 seconds, then 25 seconds. Around 30 seconds in I change the vertical to 10mV/div and no more resets happen. I don't do it in this video, but I had done some more testing with larger waveforms with the scope at 10mV/div and less sensitive, and the resets still would not happen, no matter how big or small the waveform.Honestly, this is something that doesn't affect my uses anyways, and seems like OP has found how to use it to his liking, so I'm good with whatever is going on. Just posting this at this point so someone can tell me if I'm doing something wrong or misunderstanding something for my own learning.

author: rf-loop
author_rank: Super Contributor
timestamp: August 31, 2018, 08:28:11 am
content: There is also some things what users need know and what is not often rised up in talking about SDS1104X-E ands 1204X-E and information material.(I can not test it now using current latest FW fersion in SDS1202X-E model)If least one channel vertical is(1x probe) 500uV - 2mV/div (10x probe, 5mV - 20mV/div and so on)After power up it do internal "autoadjust" every 15 second!I do not know what all it do but least it do DC offset compensation adjustment.It do this also with other time bases and modes but it is extremely well visible if ROLL mode is in use.In other than roll mode it can see sometimes as just very short "hick-up".But try 5s/div and ROLL. You can see it roll only to around 3div from right to left and then resets. It do this reset in all time bases but here with slow ROLL modes it can see very clearly (until this autoadjust process stops. This autoadjust can not turn off by user - least at this time).After internal temperature equilibrium and some timer after power up it stops this fine adjust procedure.This procedure is important in this sensitivity class when front end analog range is from DC to VHF and there is not more advanced (and expensive!) front end design. (typically after start it takes around 30min)

author: nctnico
author_rank: Super Contributor
timestamp: August 31, 2018, 09:03:06 am
content: So the first half hour you can't use roll-mode?

author: Fungus
author_rank: Super Contributor
timestamp: August 31, 2018, 10:39:53 am
content: Quote from: nctnico on August 31, 2018, 09:03:06 amAnd if it was a Rigol this "feature" would have its own thread by now.

author: rf-loop
author_rank: Super Contributor
timestamp: August 31, 2018, 03:39:13 pm
content: Quote from: nctnico on August 31, 2018, 09:03:06 amIf use 5mV/div or higher, just normally.This affect only 2mV/div, 1mV/div and 500uV/div (some scopes do not even have these ranges except digitally magnified from 4-5mV/div.)Why I tell this that it is always good that user know his equipment.But, so or so, I hope Siglent add setting what example SDS2000X series have. There user can select if autoadjust is on or off (for most sensitive vertical ranges. If user select off then he accept some DC offset may drift until thermal equilibrium.Or buy more expensive scope.

author: rf-loop
author_rank: Super Contributor
timestamp: August 31, 2018, 05:01:58 pm
content: Quote from: Fungus on August 31, 2018, 10:39:53 amRigol do not even have this V/div true range what have this phenomenon.And I do not remember how much Rigol drift after gold start. I think I have some test image somewhere but least at this time I can not find it and it is not so important.Also example my many other equipments need warm up time. Some even much more than just half hour if do its most sensitive measurements. Some may need even several days waiting before can do any accurate things... but different peoples world are so different. If I need ultra fast do some things I take my old analog scope.. it do not boot tens of seconds and what ever I turn and change all happend without any eyes detectable delays...If I need do small signals work (rare) and if I then also need use roll mode (rare) then we are in range1/rare^2 so very rare that I need this combination and also that I need it just after I have turned scope on. Normally many serious measurements need setup arrange and at this time scope can be powrred. If need this immediately (rare) and very low signal (rare) and using continuous Roll mode (rare) now we are in 1/rare^3..So I can not see this is big problem at all in real practice. But of course - it can be better but also many more things can be better and then what arew they priority... if we want all better it leads easy to price*10

author: JBeale
author_rank: Frequent Contributor
timestamp: August 31, 2018, 10:19:23 pm
content: Quote from: rf-loop on August 31, 2018, 08:28:11 amVery interesting! I saw exactly that also with the slower timebase Roll settings, but then it went away later and I assumed it was from my new trigger settings. I understand why Siglent did this (due to DC offset drift) but it would be nice to know about this so we do not all waste our time trying to reproduce something that quietly goes away after the scope warms up. I wonder if there is any other behavior that the scope quietly changes during operation without telling you.Another observation: if you lock up the scope (eg. trying to dump a scope trace over Ethernet via telnet to port 5025, and the interactive session closes after receiving too many binary characters) then no buttons on the scope work, including the power button. Not a good feeling.

author: N8AUM
author_rank: Regular Contributor
timestamp: September 01, 2018, 12:02:08 am
content: With my 1202X-E I will get continuous roll if the the trigger is set to AUTO. If trigger is set to manual than it starts over with every sweep.

author: Fungus
author_rank: Super Contributor
timestamp: September 01, 2018, 08:04:37 am
content: Quote from: rf-loop on August 31, 2018, 05:01:58 pmSo? The Rigol doesn't have any measurable problems with jitter but doesn't stop people making a whole "Project Yaigol" thread.Quote from: rf-loop on August 31, 2018, 05:01:58 pmMost need some warmup, yes, but not all of them reset the display every 15 seconds for 30 minutes after every power-on.

author: pgib8
author_rank: Newbie
timestamp: November 09, 2021, 01:11:13 pm
content: @rf-loop thank you so much for this explanation! i was having the same issue and going crazy because I could not stop the screen from resetting. After reading this and approximately 30 minutes later, the screen stopped resetting all on its own, just like you said!

author: Caliaxy
author_rank: Frequent Contributor
timestamp: November 09, 2021, 02:40:10 pm
content: Quote from: nctnico on August 31, 2018, 09:03:06 amThat's a perfect example of a reason why some people often prefer simple A-brand oscilloscopes that just work, such as Keysight 1000x (if they can afford, of course).B brands came a long way and don't seem to slow down (kudos to them), but they are not there yet. Sometimes they just sit between you and your job. Instead of debugging your DUT, you start debugging your tool, to the point you forget what you were doing in the first place.