AC vs DC triggering... since this seems to largely be a square wave issue, could the trigger be triggering off harmonics (randomly), and that's the cause of the jitter?
I have seen this happen before with oscilloscope triggers but the harmonics are synchronous with the square wave so this would not by itself explain the jitter. When it happens, the trigger occurs after or sometimes before the fundamental of the square wave but is relatively stable. It usually indicates a problem with the trigger circuits.
Huge thanks for responding Rigol! Sounds like the 5us trigger bug probably got fixed in a firmware Dave isn't running (but who knows). Dave, can you show/post which firmware/hardware you're running on the 1000z and 2000 dso's? Or could be the calibration (which I've done since I've had the scope). I'm not seeing the 5ns jitter, but I certainly see the AC coupled triggering jitter. wow. But, can't say I have any use for it. =)
We tested 3 DS1000Z scopes here with different board revisions including the FW and HW used by Dave. Screenshots of the results in the attachment.
None of the scopes showed the problem at all.
AC trigger coupling
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I can’t think of any use cases on this scope where you would want to AC couple the triggering of a DC coupled channel. It doesn’t work for me. If anyone is willing to share insight with us please follow this link to help us improve the interface.
http://beyondmeasure.rigoltech.com/acton/form/1579/0019:d-0001/1/index.htm
Here is a summary of the questions after the link in case you want a sneak peak:
• How often do you use AC coupling on your scope?
• When you use AC coupling on a channel, why do you do it?
• When you trigger on a AC coupled signal how often do you want to view that signal DC coupled on the display? If you do, please explain the use case.
• If you do this, how do you want the trigger level shown on the display since it is now decoupled from the signal visualization on the display?
Lastly, if anyone has questions or concerns they want to discuss with us, we are always here. Contact your local Rigol office or distribution partner. Our USA number is 877-4-RIGOL-1. Every DS1000Z bought in the USA is under our 3 year warranty program and Rigol quality is important to us all over the world.
Thanks,
Chris Armstrong
Director of Product Marketing & SW Applications
Rigol Technologies USA
AC trigger coupling
.
.
.
I can’t think of any use cases on this scope where you would want to AC couple the triggering of a DC coupled channel. It doesn’t work for me. If anyone is willing to share insight with us please follow this link to help us improve the interface.
http://beyondmeasure.rigoltech.com/acton/form/1579/0019:d-0001/1/index.htm
Here is a summary of the questions after the link in case you want a sneak peak:
• How often do you use AC coupling on your scope?
• When you use AC coupling on a channel, why do you do it?
• When you trigger on a AC coupled signal how often do you want to view that signal DC coupled on the display? If you do, please explain the use case.
• If you do this, how do you want the trigger level shown on the display since it is now decoupled from the signal visualization on the display?
Lastly, if anyone has questions or concerns they want to discuss with us, we are always here. Contact your local Rigol office or distribution partner. Our USA number is 877-4-RIGOL-1. Every DS1000Z bought in the USA is under our 3 year warranty program and Rigol quality is important to us all over the world.
Thanks,
Chris Armstrong
Director of Product Marketing & SW Applications
Rigol Technologies USA
Note: I do not have any Rigol scope today but this whole question about separately set trigger coupling AC when trigger source is signal channel where is also AC/DC coupling and specially when we talk scopes what have digital side trigger generation, is common, not brand related.
• How often do you use AC coupling on your scope?
Very often.
• When you use AC coupling on a channel, why do you do it?
For block DC / very low f AC from signal. One simplest example is testing power supplies ripple.
But then also I use sometimes oscilloscope input DC coupling but external very low freq corner DC block for analyze very low freq signals but blocking still DC from signal. (some example is also example some amplifier etc 1/f noise)
• When you trigger on a AC coupled signal how often do you want to view that signal DC coupled on the display? If you do, please explain the use case.
If your guestion is: Signal input A and input coupling DC and Trigger coupling AC and trigger source from this same channel A.
Answer is: Never. (exept in some very rare cases with some old analog scope for finding trigger stability)
Specially in cases that trigger is generated digitally from digitized signal somewhere after ADC.
And if I have understood right Rigol these models have digital trigger if source is input channel.
In this case also if signal input A and input coupling AC and Trigger coupling AC and trigger source from this same channel A.
Answer is: Never.
I can not imagine any need in this case for set trigger coupling AC in this kind of oscilloscope where trigger is derived from digitized side of main channel. This setting in this setup combination can remove from scope menu.
In old analog scopes where trigger is analog derived from input or ext trig and also both AC/DC couplings are in separate independent pathways my answer is different but not handle it here.
• If you do this, how do you want the trigger level shown on the display since it is now decoupled from the signal visualization on the display?
If someone do this my opinion is that he do not really understand what he is doing and what he want. Exept if want find feature (setup) what do not need occur at all.
Then, but this is totally different case.
If talk about EXT trig channel, this is different case. (btw, how Rigol produce trig there. Analog comp. method? I have not seen ADC there.
So or so but there this EXT trig channel input coupling need of course have also AC.)
When signal source is main channel where is selectable input AC/DC coupling, and trig is produced from main channel digitized data, there is no need for separate trigger AC/DC coupling. Who can logically explain what useful it may do and for what it is implemented.
There is no real inherent jitter in those captured signals, so I’d expect a FW solution if there is a verified problem on some units after a self-cal.
There is no real inherent jitter in those captured signals, so I’d expect a FW solution if there is a verified problem on some units after a self-cal.
I performed a self-cal yesterday, makes no difference.
I'm pretty convinced that it is an issue with frequency modulation of the system clock. That would go a long way to explain why no one can replicate the issue using scopes own function generator, yet there is an abundance of people who can with external generators.
I performed a self-cal yesterday, makes no difference.
Or is there a special settings that is needed in order to reproduce the jitter?
Or is there a special settings that is needed in order to reproduce the jitter?
Some reports seem to indicate it is rise-time related. Mine was sub 20ns I think.
I did not expect anyone to so badly confuse AC trigger coupling with AC input coupling. I'm pretty sure I showed I was using the trigger menu more than once in the video, and mentioned it was trigger coupling.
There is no real inherent jitter in those captured signals, so I’d expect a FW solution if there is a verified problem on some units after a self-cal.
I performed a self-cal yesterday, makes no difference.Yep, me too. No difference.
I'm pretty convinced that it is an issue with frequency modulation of the system clock. That would go a long way to explain why no one can replicate the issue using scopes own function generator, yet there is an abundance of people who can with external generators.
Do Rigol (DS1000Z and/or DS2000) use conventional trigger principle (top in image) or true digital trigger system (bottom in image).
If trigger system is digital, then: What is exactly trigger coupling AC doing there? How it is implemented in this case. (And for what purpose this setting is in this case)
I can't reproduce either errors on my DS1074Z-S (Software version 00.02.03.SP5), by using the internal Function generator.
Hardware versions?
Alexander.
But, important, there are some more bugs in the trigger system (at least DS2000A):
a.) Setting "Ext.-Trigger" with "AC-Coupling" don't work et all. The extern trigger is always DC coupled.
b.) Same with the LF- and HF-reject on extern triggering: Don't work.
c.) Using extern trigger in DC-mode cause some jitter too, but not as much as with AC-trigger on a channel.