Author Topic: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems  (Read 401537 times)

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Offline Dave Turner

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #100 on: November 14, 2014, 10:28:30 pm »
DS1074Z-S November 2013
SW 00.02.00.SP1
Board rev unknown.

Reset scope to default.

Using internal signal-generator source 1 at 15MHz square wave, 1v amplitude, high impedance, direct BNC-BNC connection to Ch2.

Run auto setup and select rising edge. (An oddity with my scope is that if a signal is present on Ch1 then Ch4 is also detected, hence use of Ch2. Anyone else found this?)

Trace looks fine.

a) Select trigger menu - coupling - AC and jitter is BX-AX approx 8.2ns.

b) Rerun Auto setup. Change Horizontal scale to 1us, change horizontal position to 5us, change Horizontal scale back to 5ns (as set by auto setup and rising edge).

No difference in trace.

Assuming I've tested correctly - with my scope I can verify the AC jitter but not the 5us issue.
 

Offline Carrington

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #101 on: November 14, 2014, 10:29:03 pm »
The AC coupled trigger jitter problem doesn't occur when using probe compensation signal output but does occur when using an equal signal (square, 1 kHz, 3 Vpp) generated  with a function generator.

That is interesting!

Yes it is!

Probably there are a big difference in the rise time.

Someone else can replicate it.
My English can be pretty bad, so suggestions are welcome. ;)
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Offline (In)Sanity

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #102 on: November 14, 2014, 10:36:12 pm »
I've confirmed this issue with my DS2000A series.   5 Mhz signal,  AC coupled trigger,   lot's of jitter.  Interesting that the LF Reject option significantly reduces it.   Perhaps it's picking up some internal clock.   IDK,   I doubt it's a software fix,  unless perhaps FPGA upgrade. 

Jeff
 

Offline Carrington

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #103 on: November 14, 2014, 10:37:39 pm »
Also if I remember correctly, I have read somewhere in the forum that the DS4000 series uses analog trigger instead digital.
Can anyone confirm this?
My English can be pretty bad, so suggestions are welcome. ;)
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Offline TheGreatGooglyMoogly

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #104 on: November 14, 2014, 10:40:24 pm »
My late $0.02:

The brand new DS2302A we have in the lab here seems just fine in both AC and DC modes.
I measured a 74.25 MHz and a 54 MHz clock on an FPGA board, using AC and DC triggering and 0/5 us delay.

This was a scary video since yesterday we had a major jitter issue with a 27 MHz clock output of a video decoder chip. Turns out the clock is jittery not the 'scope!


PS... what's a 'walkabout' ?
 

Offline (In)Sanity

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #105 on: November 14, 2014, 10:42:51 pm »
I'm going to go out on a limb here and say it's either picking up the LCD display back light freq or the switch mode power supply.  Most likely the display. 

The LF Reject option significantly reduces it,  but doesn't remove it.   

What can I say,  I like limbs.

Jeff
 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #106 on: November 14, 2014, 10:48:22 pm »
Has anyone tested this with a good old fashion analog  ~20 Mhz sig gen ? 

Yes, I get the same result on my 4000 series with a 20Mhz OCXO.
« Last Edit: November 14, 2014, 10:50:46 pm by dr.diesel »
 

Offline miguelvp

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #107 on: November 14, 2014, 10:52:10 pm »
Does bandwidth limiting to 20MHz make a difference?
 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #108 on: November 14, 2014, 10:55:22 pm »
Does bandwidth limiting to 20MHz make a difference?

Nope, not on mine, delay jitter anyhow.  (I don't see the AC/DC trigger coupling issue on the 4000)

Offline xs4hkr

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #109 on: November 14, 2014, 11:16:46 pm »
The AC coupled trigger jitter problem doesn't occur when using probe compensation signal output but does occur when using an equal signal (square, 1 kHz, 3 Vpp) generated  with a function generator.

That is interesting!

Yes it is!

Probably there are a big difference in the rise time.

Someone else can replicate it.

Yes, there is. The probe compensation signal output has an avg. rise time of 2.8 us, the signal of the generator has an avg rise time of 19.4 ns. See attachments.

 

Offline Rory

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #110 on: November 14, 2014, 11:31:30 pm »
Wondering if jitter occurs with external trigger...
 

Offline Marco

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #111 on: November 14, 2014, 11:36:38 pm »
Maybe they use analogue triggering after all and their circuits are just really crappy? I guess it might be a little cheaper, digital triggering will take a little extra space on the FPGA for wirespeed processing and FIFO/circular buffer.
 

Offline wn1fju

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #112 on: November 14, 2014, 11:37:43 pm »
My 1104Z exhibits both the 5us and AC trigger jitter.  However, I just tried the same experiment on an mid 1990's HP 83475B scope (the same as an HP 54610B with the addition of an optical sensor).  And I got the same jitter problem on the HP scope, namely if I move the horizontal delay, the waveform (in this case a 20 MHz square wave) exhibits jitter.  See the photos.  Since my methodology was to 1) get a stable trace at 5 ns/div, 2) crank the time base way up so I don't have to keep turning the delay knob forever, 3) set the delay, 4) crank the time base back down to 5 ns/div, perhaps the problem is that the acquisition rate changes when the time base is set slower and at that point, the delay is somehow geared to that acquisition, so that when I go back down, things are upset.  Of course, the HP 54610B does everything the old way through repetitive sampling to build up the waveform.  Just a thought.
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #113 on: November 14, 2014, 11:47:42 pm »
In seeking more information about this issue, I read this App-note by Agilent that talks about ADC interleaving and the effect of inaccurate phase alignment and vertical calibration of a scopes input data acquisition circuits.
http://cp.literature.agilent.com/litweb/pdf/5989-5732EN.pdf

I am not sufficiently expert to advance the discussion but I did want to post this link so that someone who has read this App-note or is prepared to read it can comment on whether it may be related. It does have some testing suggestions for those with suitable equipment to perform.

Naturally it shows Agilent scopes performing closer to the ideal and doesn't mention Rigol at all.

It is an interesting document in its own right anyway, even if it proves to be off topic for this thread.

Aliasing is a real problem but does not explain why the Rigols display large amounts of jitter with AC coupling of the trigger and low amounts 5us and every 10us after the trigger.

Wondering if jitter occurs with external trigger...

Do you mean the external trigger output?

The DS1054Z series has no external trigger inputs (4 channel oscilloscopes usually do not) and the DS2000A series has one.  I have never seen an evaluation of the DS2000A external trigger input but the documentation says that some trigger modes only work with the vertical input channels and not the external trigger input.
 

Offline Rory

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #114 on: November 14, 2014, 11:49:47 pm »
In seeking more information about this issue, I read this App-note by Agilent that talks about ADC interleaving and the effect of inaccurate phase alignment and vertical calibration of a scopes input data acquisition circuits.
http://cp.literature.agilent.com/litweb/pdf/5989-5732EN.pdf

I am not sufficiently expert to advance the discussion but I did want to post this link so that someone who has read this App-note or is prepared to read it can comment on whether it may be related. It does have some testing suggestions for those with suitable equipment to perform.

Naturally it shows Agilent scopes performing closer to the ideal and doesn't mention Rigol at all.

It is an interesting document in its own right anyway, even if it proves to be off topic for this thread.

Aliasing is a real problem but does not explain why the Rigols display large amounts of jitter with AC coupling of the trigger and low amounts 5us and every 10us after the trigger.

Wondering if jitter occurs with external trigger...

Do you mean the external trigger output?

The DS1054Z series has no external trigger inputs (4 channel oscilloscopes usually do not) and the DS2000A series has one.  I have never seen an evaluation of the DS2000A external trigger input but the documentation says that some trigger modes only work with the vertical input channels and not the external trigger input.

Yes I was referring to the DS2000 series external trigger input. But as a second thought, I don't recall if there is an AC coupling selection for that input in the triggering menu.
« Last Edit: November 14, 2014, 11:51:19 pm by Rory »
 

Offline Nonorthogonal

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #115 on: November 14, 2014, 11:51:31 pm »
When will someone crack open theirs and try to find the same frequendy mod on the front end?  >:D
 

Offline Carrington

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #116 on: November 15, 2014, 12:06:38 am »
The AC coupled trigger jitter problem doesn't occur when using probe compensation signal output but does occur when using an equal signal (square, 1 kHz, 3 Vpp) generated  with a function generator.

That is interesting!

Yes it is!

Probably there are a big difference in the rise time.

Someone else can replicate it.

Yes, there is. The probe compensation signal output has an avg. rise time of 2.8 us, the signal of the generator has an avg rise time of 19.4 ns. See attachments.

When you checked the AC jitter using the probe compensation output, what timebase did you use, between 2 and 10 ns or 2us?

Because evidently at 2us you can't appreciate it.
« Last Edit: November 15, 2014, 12:10:22 am by Carrington »
My English can be pretty bad, so suggestions are welcome. ;)
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Online rs20

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #117 on: November 15, 2014, 12:17:21 am »
Oh Dave, IMHO perhaps you should have been very explicit that you were talking about AC *trigger* coupling, not AC *signal* coupling. I can't tell what proportion of people, especially in the YouTube comments, actually understand the distinction (I sure didn't know AC trigger coupling even existed until watching this video; I'm struggling to contrive applications for it), and I see at least a few people who quite clearly don't and think that AC coupling is broken. Then again, if you were to be completely clear about every little thing, your videos would be 24 hours long, so I do understand that this is a tricky balance.

Also, more importantly:

The issue with the clock signal not generating the eye diagram you expected is not a bug -- the holdoff is a user-defined value; if that value is such that the next edge after a rising edge + holdoff delay is another rising edge, then you'll lock onto those rising edges and get rising edges all day long. A randomly chosen holdoff value has a 50/50 chance of either A) finding alternating rising/falling edges (good eye diagram), or B) finding only one or the other forever (apparently "ignoring" your request to detect both edges). By modifying the holdoff value on my DS2202, I can easily transition from A, to B (holdoff half a period longer), to A (holdoff a full period longer), to B, etc etc -- exactly as you would expect. I'd expect even analog scopes (do they have a holdoff knob?) to behave the same way; if they don't, that needs explaining. Generating eye diagrams on actually interesting data signals works fine on my DS2202 more-or-less regardless of holdoff value since the random data randomizes which edge is found next. I haven't explained myself to well, but hopefully y'all can see what I mean -- in short, that particular "issue" is totally not a bug at all, it's doing precisely what you asked for.

EDIT: To be clear, I'm not exactly defending Rigol, my opinion is:
-- Oscilloscope "ignores" request to trigger on both rising and falling edge: Not a bug at all
-- AC trigger coupling issue: Really weird bug that needs to be fixed, but the impact is miniscule compared to what it would be if AC signal coupling was broken.
-- The 5us thing: Bad bug that needs to be fixed.
« Last Edit: November 15, 2014, 12:51:53 am by rs20 »
 

Offline lewis

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #118 on: November 15, 2014, 12:19:34 am »
Shite.... buy an Agilent.
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Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #119 on: November 15, 2014, 12:26:05 am »
And I got the same jitter problem on the HP scope, namely if I move the horizontal delay, the waveform (in this case a 20 MHz square wave) exhibits jitter.  See the photos.  Since my methodology was to 1) get a stable trace at 5 ns/div, 2) crank the time base way up so I don't have to keep turning the delay knob forever, 3) set the delay, 4) crank the time base back down to 5 ns/div, perhaps the problem is that the acquisition rate changes when the time base is set slower and at that point, the delay is somehow geared to that acquisition, so that when I go back down, things are upset.  Of course, the HP 54610B does everything the old way through repetitive sampling to build up the waveform.  Just a thought.

The jitter of the source and the sample clock add when using a delayed acquisition and whichever is worse will limit timing accuracy.  The displayed behavior of the Rigol when used with a source which has low jitter as measured on other oscilloscopes is odd because the jitter is significant and maximum with 5us of delay and repeats every 10us after that while the jitter at 10us and every 10us after that only appears to be that of the source and trigger.

When I run this test on my 2440, jitter is about equal to the level expected from just the trigger noise out to 10us and beyond.  It actually measured just under 200ps at the trigger and just over 200ps at the delay point which matches the specifications and there was too small a difference to say whether the oscilloscope timebase or the source had more long term jitter.
 

Offline xs4hkr

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #120 on: November 15, 2014, 12:29:54 am »
The AC coupled trigger jitter problem doesn't occur when using probe compensation signal output but does occur when using an equal signal (square, 1 kHz, 3 Vpp) generated  with a function generator.

That is interesting!

Yes it is!

Probably there are a big difference in the rise time.

Someone else can replicate it.

Yes, there is. The probe compensation signal output has an avg. rise time of 2.8 us, the signal of the generator has an avg rise time of 19.4 ns. See attachments.

When you checked the AC jitter using the probe compensation output, what timebase did you use, between 2 and 10 ns or 2us?

Because evidently at 2us you can't appreciate it.

Good point. 2 us (compensation signal) and 10 ns (generator signal). But with the slower rise time that's the only way to get a reasonable representation of the signal.
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #121 on: November 15, 2014, 12:30:47 am »
I'd expect even analog scopes (do they have a holdoff knob?) to behave the same way; if they don't, that needs explaining.

Most analog oscilloscopes support trigger holdoff or at least most of mine do.  It is hardly a rare feature if only because it is so easy to add.
 

Offline TheGreatGooglyMoogly

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #122 on: November 15, 2014, 12:32:32 am »
Oh Dave, IMHO perhaps you should have been very explicit that you were talking about AC *trigger* coupling, not AC *signal* coupling. I can't tell what proportion of people, especially in the YouTube comments, actually understand the distinction (I sure didn't know AC trigger coupling even existed until watching this video; I'm struggling to contrive applications for it), and I see at least a few people who quite clearly don't and think that AC coupling is broken. Then again, if you were to be completely clear about every little thing, your videos would be 24 hours long, so I do understand that this is a tricky balance.

HOLD THE CARRIAGE

I missed the AC trigger coupling. On the DS2302A, AC coupling causes the same jitter as seen in the video here. DC/AC input coupling don't seem to affect it. LF reject improves it, but not enough.

 

Offline staze

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #123 on: November 15, 2014, 12:35:41 am »
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?
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Offline Carrington

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #124 on: November 15, 2014, 12:37:28 am »
Good point. 2 us (compensation signal) and 10 ns (generator signal). But with the slower rise time that's the only way to get a reasonable representation of the signal.
:palm:
Obviously, but we want see if there are any jitter, however with a rise time of 2.8us at a time base of 10ns, complicated...
« Last Edit: November 15, 2014, 12:58:05 am by Carrington »
My English can be pretty bad, so suggestions are welcome. ;)
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