Rigol and Multiple triggering - individual triggering on each channel - Page 1
Forum section: electronics / testgear

author: pascal_sweden
author_rank: Super Contributor
timestamp: January 02, 2014, 12:31:16 pm
content: Does the Rigol DS1000Z series and/or DS2000/A series provide multiple triggering (individual triggering on each channel)?

author: EV
author_rank: Frequent Contributor
timestamp: January 02, 2014, 01:24:30 pm
content: If you mean alt-trigger, DS2000 does not have it.

author: pascal_sweden
author_rank: Super Contributor
timestamp: January 02, 2014, 10:24:03 pm
content: I am a bit dummy on scopes here.If you have Channel 1, you can set trigger on edge, and signal is shown on current time scale.But then for Channel 2, the signal is shown in same time scale, and not triggered to any edge?Do some scopes have triggering on each signal individually? But how are the signals then displayed? In separate windows and time scales?What are the use cases? Isnt there always 1 common reference?Would like to hear about the different use cases/advantages/disadvantages.Again I am a dummy on this topic, so bear with me.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 03, 2014, 09:33:47 am
content: Quote from: pascal_sweden on January 02, 2014, 10:24:03 pmYes. Because you want to see how Sig2 correlates or relates to Sig1. With the same time-base, or frame of reference.QuoteYes. Dual time-bases have been around a long time. They can be correlated (simply time-delayed, or offset), or independent (alternating).QuoteYes. How else could it be? Well, not in a "window" or box, necessarily. But offset vertically, and with their own time axis.QuotePerhaps you have an event on Sig1, that you need to see in high temporal resolution (say, microseconds). But then there's a 2nd event that follows, a "long time" later (say milliseconds). With a time-delay, you can shift Sig2 so it can be seen with the same high-rez as Sig1, on the same screen. Without it, you can see them both only when zoomed far out, and you can zoom in on only one at a time.And no, there's not always 1 common reference. With alternating time-bases, a single scope can trigger first on Sig1, then next on Sig2. Back and forth. They alternate, which essentially gives you two scopes in one... though you could get the same result with 2 separate scopes. The downside is that each channel gets only half the # of trigger events, because you've split the scope.That's all the education I have time to dispense today. Rather than saying "I'm a dummy", why not take a class, or read a book, or spend some time on-line reading? The web these days is a vast cornucopia of knowledge. Not much reason for anyone to say they know nothing, other than laziness.If you feel you might need this dual-timebase capability, take a look at something like the Rigol DS1052E, which supports it. Along with another feature missing from the current gen of cheap scopes... Equivalent Time sampling. To provide sampling rez of 25 GSa/s, 50, or even more! But only with repeating signals with stable time/phase, which isn't always easy to come by (and possibly why it was dropped).The 1052E is very cheap, only $329 or less. You could probably find a used one even cheaper, and use it as a "starter scope", to gain some basic knowledge. And exit the "dummy domain".Then sell it to the next newbie in line, to reap similar benefits. That way you'll be in a much better position to really know what you need/want in a scope, without having spent a large sum of money prematurely.

author: marmad
author_rank: Super Contributor
timestamp: January 03, 2014, 02:36:16 pm
content: Quote from: Mark_O on January 03, 2014, 09:33:47 amI believe the reason Alt-Trigger is not present in the current line of less-expensive DPOs (Agilent X-Series, Rigol UltraVision, etc) is because it would be difficult to support intensity-grading of two distinct time bases at a reasonable speed. In some situations, you can at least achieve a stable display of two non-time-correlated waveforms by using one of the dual source triggers of the Rigol - such as the Delay or Duration Trigger - which allows you to trigger after edges (or other conditions) from each channel with an adjustable </>/<>/= time between them.

author: Mark_O
author_rank: Frequent Contributor
timestamp: January 03, 2014, 02:57:20 pm
content: Quote from: marmad on January 03, 2014, 02:36:16 pmWould it?QuoteI'm glad you mentioned that, because that's a capability I hadn't considered, to incorporate dual-channel triggering.

author: marmad
author_rank: Super Contributor
timestamp: January 03, 2014, 05:32:59 pm
content: Quote from: Mark_O on January 03, 2014, 02:57:20 pmWell, I'm not sure, but it would require two distinct intensity buffers - plus the very nature of DPOs is fast waveform updates, so the sampling is highly optimized. It's been awhile since I've had a scope with alt-trigger, but I seem to remember that you can really fool around with both trigger offsets and delays - so that the whole display updating can get a bit slow and choppy. Anyway, it's just a theory - otherwise it seems strange it wouldn't be implemented, since it's simple to do.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 25, 2014, 10:35:11 pm
content: Does any of the Rigol scopes out there have support for dual time bases?

author: Gixy
author_rank: Regular Contributor
timestamp: October 27, 2014, 10:31:51 am
content: Dear all,Happy owner since a few days of an MSO2072A (changed into an MSO2302A...), I just tried to visualize two signals on this scope, doing the same thing on an old Tek scope (2445A).- one signal is the 1MHz 0,4V calibration signal from the Tek (square pulse)- the other is a 1MHz 3.3V signal (square pulse) generated by an LTC6904 programmable oscillatorIn normal trigger mode, if triggered on one channel, neither the Tek nor the Rigol can stabilize simultaneously the two signals.In "Vert" mode, the Tek perfectly stabilize the two traces (in this mode, it triggers on the first raising edge among the two channels)I can obtain something less unstable wih the Rigol scope by playing with advanced trigger modes (delay in particular), and by setting the maximum memory size (28Ms).Furthermore, I noticed that if I change the Volt/div setting, the minimum voltage level at which trigger occurs is changing. For exemple with the 3.3V signal:- 500mV/div gives 0.2mV for triggering-1V/div gives 0.680V- 2V/div gives 1.65V- 5V/div never triggersIf I use AC coupling for triggering, triggers occurs from 0V to a level which also depends on the V/div setting.Are these behaviours normal or something is going wrong with my brand new toy?Thanks for all the precious information given in this forum!Denis

author: pa3bca
author_rank: Regular Contributor
timestamp: October 27, 2014, 07:38:25 pm
content: When I bought my first digital scope (6 yeas ago after my old analog scope died and after years of no electronics hobbying) I was surprised that it did not support alternate triggering. I remembered using it extensively 40 years ago.. (BTW my first digital scope was an OWON, what a piece of c**p that was...)But actually I have never needed or missed alternate triggering. Might be because of the type of experiments I am doing, but in general I never need two or more unrelated (in the time domain) signals to be displayed with continuous trigger. You will lose the time relationship between the signals so what is the use. With the long memory of modern scopes you can do a single shot trigger on a slow timebase and the inspect the signals (and their relation) at your leisure.Or use the method Marmad has explained above if you really need to look at live signals

author: donmr
author_rank: Regular Contributor
timestamp: October 27, 2014, 08:20:17 pm
content: This is a feature I have used a lot on higher end HP/Agilent scopes.Basically I use the first trigger (ch1) to "arm" the scope to then trigger on the event I want to see on the other channels.I still need the second trigger (ch2) because the time delay is often not fixed.I have not found it on any of the lower end scopes and that is keeping me from buying any of them (as long as I still have access to the better ones).I don't think it takes any mode memory, it just requires the scope to continue to collect data after the first trigger and switch to the second trigger criteria. That should be just a simple software function although it will impose some minimum time delay on the second trigger, the time it takes the software to change the set-up.Don

author: marmad
author_rank: Super Contributor
timestamp: October 27, 2014, 09:03:59 pm
content: Quote from: Gixy on October 27, 2014, 10:31:51 amI'm not sure why you're having difficulty. If I have two repetitive signals from different sources, I don't have a problem getting a stable display using the Delay trigger (as in attached image).QuoteWhat trigger type are you referring to? This sounds strange - e.g. using Edge trigger, I don't have any problem triggering on the full range of the waveform.Quote from: donmr on October 27, 2014, 08:20:17 pmThe DS2000 has at least four 2-channel triggers that can use both channels to validate the trigger.

author: Gixy
author_rank: Regular Contributor
timestamp: October 27, 2014, 09:35:33 pm
content: Thanks Marmad for your answer.Delay trigger is the only way I found to have the two signals more or less stabilized.The other problem is in normal mode, edge triggering and DC trigger coupling, if I change the volts/div setting of the triggered signal, the level at which the signal is stable varies. This value changes also a little if I change the vertical position of the signal. Since the trigger sensitivity is expressed in division, does the trigger consider what is displayed instead of the true value of the signal?

author: marmad
author_rank: Super Contributor
timestamp: October 27, 2014, 10:50:38 pm
content: Quote from: Gixy on October 27, 2014, 09:35:33 pmDo you mean when just using one channel? And it sounds like you mean Auto mode. If you are in Normal mode and there is no trigger, the waveform is frozen - not unstable.QuoteTrigger sensitivity? I don't know what you mean. The trigger level is expressed in volts - and it doesn't change when changing vertical scale - unless you change the scale far enough that it goes off screen.I think we might be able to help you more if you posted some images with the settings that are giving you problems, etc.

author: jancumps
author_rank: Unknown
timestamp: October 27, 2014, 11:30:01 pm
content: Quote from: pascal_sweden on October 25, 2014, 10:35:11 pmYes, the DS1052E has Alternate mode via menu Trigger -> Mode -> Alternate.Attached a very small action shot of my scope in alt mode:

author: Gixy
author_rank: Regular Contributor
timestamp: October 27, 2014, 11:48:25 pm
content: OK Mark, thanks for your help. It's late tonight here (and we just switched to winter time yesterday :-( ), so I'll post images tomorrow evening.Trigger "sensitivity" is given in divisions in the instrument specifications:- 1 div (below 10 mV or noise rejection is enabled)- 0.3 div (above 10 mV and noise rejection is disabled)

author: pa3bca
author_rank: Regular Contributor
timestamp: October 28, 2014, 04:14:08 pm
content: Quote from: jancumps on October 27, 2014, 11:30:01 pmWhich is not (the same as) dual time bases.. I assume he wants each channel to have its own time base - I suppose in addition to alternate trigger. This would be a very confusing configuration, I have no clue as to its usefulness.I am fairly certain no Rigol scope has this feature.The 1052 has alt trigger. the 1000Z and 2000 series have not. Not sure about the 4000 and 6000 but probably not.

author: jancumps
author_rank: Unknown
timestamp: October 28, 2014, 04:48:01 pm
content: Yes, agree - I could have been preciser.I reacted on the same posters original question on the possibility to have two time-unrelated channels stable on screen.

author: pa3bca
author_rank: Regular Contributor
timestamp: October 28, 2014, 04:51:43 pm
content: Quote from: jancumps on October 28, 2014, 04:48:01 pmYes.. I admin that I was initially thrown off too by his question within a question.... the OP has a history of flooding the forum with questions (within questions within questions.... etc)...

author: David Hess
author_rank: Super Contributor
timestamp: October 28, 2014, 05:09:29 pm
content: Quote from: Gixy on October 27, 2014, 10:31:51 amOn old analog oscilloscopes, VERT mode selects the output from the vertical channel switch as the trigger source so as the vertical channel switch selects alternate channels, the trigger source alternates as well. Later designs had a separate trigger channel switch but kept the VERT mode by alternately selecting the trigger source on the trigger channel switch so there was a deliberate effort to keep this capability. Some early DSOs worked this way as well allowing them to support alternate triggering very easily.VERT mode applies the same trigger settings including level to both inputs so it is not suitable for all signals or displays. The vertical trigger signal also will not work in CHOP mode but oscilloscopes with a separate trigger channel switch may add the triggers together in this case which works better than you might expect.Quote from: Mark_O on January 03, 2014, 09:33:47 amDual timebases are not necessary for alternate triggering but they do allow for alternate sweep with fully independent triggering and positioning. Besides alternate operation, dual beam oscilloscopes can display both sweeps simultaneously and some single beam oscilloscopes can chop the two sweeps to do the same thing with one beam. Either method will avoid intensity starvation of one sweep when the sweep speeds vary from each other by a lot.Quote from: marmad on January 03, 2014, 05:32:59 pmNon-DPO oscilloscopes also lack it so I suspect it is because there are other ways to achieve almost the same thing and a lack of demand for dual timebases. There would be some duplication in things like the decimation and reconstruction stage but for performance reasons, that duplication may already exist. Alternate triggering should be easy but they lack that as well with the mentioned older Rigol being a notable exception.I never really appreciated how useful dual independent timebase capability was until I got a Tektronix 7000 mainframe. The best way I have found so far to duplicate what it can do on a DSO is to use two DSOs.In a couple of different Linear Technology application notes, Jim Williams made the comment "Most oscilloscopes, whether analog or digital, will have trouble reproducing this display." in connection with the signals from a switching regulator driven Royer converter being displayed with a dual beam oscilloscope using a single timebase but I never understood why a DSO would have any problems with his example. You can find it in application note 49, 55, and 65 among other places.

author: marmad
author_rank: Super Contributor
timestamp: October 28, 2014, 05:27:35 pm
content: Quote from: David Hess on October 28, 2014, 05:09:29 pmVirtually every older generation, low-cost DSO (Rigol, Owon, Hantek, Siglent, etc) has Alternate trigger - and virtually every newer generation, low-cost DPO (Agilent, Rigol, Siglent, etc) does not. Most people that use oscilloscopes are familiar with the feature and find it handy from time to time - so I doubt it was just a simultaneous decision by every manufacturer to drop the feature at the same time. I think it's implementation on the newer DPOs is made difficult/time-consuming by either the DPO architecture or digital triggering.

author: David Hess
author_rank: Super Contributor
timestamp: October 28, 2014, 05:46:22 pm
content: Quote from: marmad on October 28, 2014, 05:27:35 pmSorry, when I was composing my post two different paragraphs got merged in a rather confusing way.The difference between the two may be that the older DSOs which lack DPO functionality can get alternate triggering for free from their analog trigger path; it just involves switching the trigger channel switch (multiplexor). It is more involved with DSOs that implement the digital trigger needed to support DPO functionality because either the digital trigger path has to be duplicated for little gain or it has to be reconfigured for each alternation.There is a similar limitation in old DSOs for dual independent timebase capability. The timebase and/or trigger circuits are recalibrated during every time/div change so implementing independent dual timebases would either require more hardware or entail a performance hit.

author: David Hess
author_rank: Super Contributor
timestamp: October 28, 2014, 05:56:26 pm
content: Quote from: pa3bca on October 28, 2014, 04:14:08 pmWhen I was evaluating DSOs a couple years ago, I could not find any which had dual independent timebases. That Rigol was the only one I ran across that had alternate triggering but maybe they were the only ones to market that as a feature. I ended up getting two less expensive DSOs to use in parallel which was also less expensive than a single 4 channel oscilloscope.I think they were more important with analog oscilloscopes because they could be used for things like delay compensation or to combine separate waveform displays into one. They operate like having two oscilloscopes with one display so you can have two 2 channel displays instead of one 4 channel display.

author: Gixy
author_rank: Regular Contributor
timestamp: October 28, 2014, 09:41:09 pm
content: Hi all,Here are the images showing the minimum trigger level variation vs vertical scale.The signal is a 3V / 1MHz square. In Auto mode as well as in Normal mode, the minimum triggering level is:- scale 500mV trigger 400mV- scale 1.00V trigger 880mV- scale 2.00V trigger 1.84V- scale 2.50V trigger 2.34V- scale 3.00V trigger 2.76Vno further triggering possible above 3V/div.There's an apparent limitation of about .92 division below which triggering is impossible. Probably as per design, but good to know.In dual traces mode (object of this thread), although the two signals have the same frequency, it is quite impossible to stabilize both perfectly. The best result is achieved with Delay triggering, but it's not as stable as the Vert (thanks David for your explanation) triggering of the Tek.

author: donmr
author_rank: Regular Contributor
timestamp: October 28, 2014, 10:03:32 pm
content: Quote from: marmad on October 27, 2014, 09:03:59 pmI don't see the type I want in the User's Guide for the DS2000If there are signals like this:________________________________Ch1: _______________________________/t2__ __ __Ch2: _________| |____| |________________________| |__________________t1 t3I want to see the activity on Ch2 at t3, the one after the edge on Ch1 at t2.Sometimes simple time delays work for this, but often the times are variable andI need to "arm" on the t2 edge, then trigger on the t3 one.Don

author: marmad
author_rank: Super Contributor
timestamp: October 28, 2014, 10:49:17 pm
content: Quote from: donmr on October 28, 2014, 10:03:32 pmIsn't it just (CH1=H AND CH2=RE); a simple Pattern trigger?

author: marmad
author_rank: Super Contributor
timestamp: October 28, 2014, 10:56:50 pm
content: Quote from: Gixy on October 28, 2014, 09:41:09 pmI don't know what's going on with your DSO, but I have absolutely no problem triggering at any level - no limitations (see images). Have you tried running a self-calibration?

author: marmad
author_rank: Super Contributor
timestamp: October 28, 2014, 11:18:09 pm
content: Quote from: Gixy on October 28, 2014, 09:41:09 pmAgain, I'm not sure why you're having problems (or if your DSO is functioning correctly), but I don't really have a problem getting a stable display using the Delay trigger. It usually takes a little playing around (both channels have their own trigger levels, etc), but eventually I can get the DS2000 to lock onto both waveforms stably.

author: rstoer
author_rank: Regular Contributor
timestamp: October 28, 2014, 11:40:47 pm
content: Quote from: marmad on October 28, 2014, 05:27:35 pmI, for one, used ALT triggering more than occasionally on my Owon, which I recently replaced with a fully loaded Agilent MSOX2022A.Now there's no question that in most ways the Agilent shines in comparison to the Owon but there are some things I miss - foremost among them is ALT triggering. I can't believe that with today's technology this can't be achieved at a decent price point. In fact, I wonder why we can't have a reasonable priced dual time base scope, with ALT triggering relegated to entry level equipment.I guess I'm alone in this but I can't imagine what the use is of having four analog channels without ALT triggering or a dual time base.

author: Gixy
author_rank: Regular Contributor
timestamp: October 28, 2014, 11:47:02 pm
content: Ooops,After calibration, things changed a lot: trigerring is now independent of V/div and stabilization is much better in delay mode.Strange, as this unit was last factory calibrated in june...Anyway, it works now, thanks for your help Mark!

author: marmad
author_rank: Super Contributor
timestamp: October 29, 2014, 12:48:17 am
content: Quote from: Gixy on October 28, 2014, 11:47:02 pmI'm happy to hear that fixed it - and glad I could help!

author: marmad
author_rank: Super Contributor
timestamp: October 29, 2014, 12:57:03 am
content: Quote from: rstoer on October 28, 2014, 11:40:47 pmThere are nice things about the Agilent 2000 X-series, but the triggers are not one of them; it has a really weak assortment of triggers - having just the Pattern trigger as it's sole trigger which can accept two inputs.

author: donmr
author_rank: Regular Contributor
timestamp: October 29, 2014, 05:43:48 pm
content: Quote from: marmad on October 28, 2014, 10:49:17 pmYes, sorry, I should have shown the signal on CH1 as a pulse.

author: marmad
author_rank: Super Contributor
timestamp: October 29, 2014, 06:54:02 pm
content: Quote from: donmr on October 29, 2014, 05:43:48 pmNow it just seems like the Delay trigger on the DS2000 could handle it easily - just set both CH1 and CH2 to RE, and the delay to < the maximum you want to be considered the 'arming' time.

author: donmr
author_rank: Regular Contributor
timestamp: October 29, 2014, 07:01:38 pm
content: Quote from: marmad on October 29, 2014, 06:54:02 pmThe description in the User's Guide looks like that expects two synchronous signals and tests for the skew.It might work for my situation too, I'd have to see it used that way.Thanks for your info.

author: marmad
author_rank: Super Contributor
timestamp: October 29, 2014, 07:06:19 pm
content: Quote from: donmr on October 29, 2014, 07:01:38 pmNo problem. We've already been discussing the fact that it can be used on two non-synchronous signals in this thread - quite similar to the Alternate trigger - and I've posted two images in previous posts,hereandhere, showing stable triggering on two wildly different frequencies from different sources.