Author Topic: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems  (Read 393966 times)

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Offline Owen

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #200 on: November 15, 2014, 06:23:53 pm »
I've tested my DS2000 Series using AC coupling Mode on the trigger: I've fed in a sine wave with 500 mV offset and frequency of 1 MHz, but didn't terminate it proper. And it looks okay so far, if i'm getting higher with frequency it starts jittering around. So with signals less than < 1 MHz there is no jitter. If I really need to use AC coupling Mode i would probably use the avarage mode (32 Samples) and just filter it this way. But to be honest i've never used that AC trigger coupling mode before :).
 

Offline Fagear

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #201 on: November 15, 2014, 07:25:00 pm »
Sorry, I'm helpless with English translation in Youtube editor... Takes too much time. |O
I hope, it will be clear without translation. :palm:
??????? ????????????? ????????????? Rigol

03:57 - my "signal source"
04:56 - testing for problem #1 on DS2000 (can't check it, bad signal source)
08:07 - testing for problem #2 on DS2000 (confirmed)
11:14 - testing for problem #3 on DS2000 (not confirmed)
13:27 - testing for problem #4 on DS2000 (confirmed)
18:43 - testing for problem #1 on DS4000 (can't check it, bad signal source)
19:37 - testing for problem #2 on DS4000 (confirmed in a strange way)
22:47 - testing for problem #3 on DS4000 (not confirmed)
23:02 - testing for problem #4 on DS4000 (not confirmed)
« Last Edit: November 15, 2014, 07:31:37 pm by Fagear »
 

Offline miguelvp

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #202 on: November 15, 2014, 07:54:08 pm »
I don't know Russian but I could understand a lot of it, nice video   :-+
 

Offline Bud

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #203 on: November 15, 2014, 08:45:24 pm »
A DS2072A here with HW v2.0. Practically no 5us trigger offset jitter. AC coupling trigger jitter does present.

Do not know if this helps or makes it more puzzling but accidentally discovered that AC Coupled trigger jitter is cured if to set trigger type from Edge to Runt or Window type (play with trigger  level controls to stop the jitter). Please check on yours.
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Offline miguelvp

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #204 on: November 15, 2014, 09:01:17 pm »
I think only Edge triggering supports AC coupled trigger.
At least on mine that's the only one that has the option.
 

Offline Bud

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #205 on: November 15, 2014, 09:54:55 pm »
I now see what you mean. With trigger type set to Runt or Window, trigger coupling DC/AC selection tab disappears.
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Offline silicon_ghost

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #206 on: November 15, 2014, 09:55:49 pm »
I just tested this on my Rigol DS4024 scope (channel 1 only).  I see a little bit of what Dave Jones demo'd in the video.  I don't see any difference from AC or DC coupled triggering so I'm only showing DC coupled trigger screen prints.

I fed in 5 and 50 MHz square waves from a Rigol DG4162.  I played with plenty of combinations of DC or AC trigger coupling, trigger delays from 0 to ~10 us, and different timebases.  You will see that the transition from clean to jittered triggering is dependent on the timebase used.

Scope details
- DS4024
- S/W Ver 00.02.01
- H/W Ver 1.2
 

Offline wn1fju

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #207 on: November 15, 2014, 09:57:14 pm »
All I know is that I tried the following signal generators (all at 20 MHz):

HP 3314A
Wavetek 288
HP 3335A
HP 8782A

The first two are generic function generators and the last two are RF synthesizers with ovenized oscillators.

These four were all tried against the following digital scopes:

Rigol DS1104Z
HP 54610B
HP 54112D
Fluke PM3390B
Tek TDS350

Every scope but the Tek showed the following:

no jitter at 0 delay with any of the four sources
plenty of jitter at sufficient nonzero delay, but ONLY with the first two function generators
no jitter at sufficient nonzero delay with the two RF ovenized synthesizers

Now, all the non-Rigol scopes use equivalent time sampling and it seems clear that in the absence of a stable source, such as the synthesizers, the combination of sampling and delay leaves one with a "jittered" presentation after the wandering waveform builds up.

Apparently, the Rigol is doing some analog of equivalent time sampling (???) since I get exactly the same behavior - OK only with the synthesizer sources.   

Incidentally, the Tek scope passes the test because it cheats - it won't let you set the delay large enough to cause a problem.

Anyway, I feel a lot better now knowing that my 1980-1990 scopes are just as good as my 2014 scope!
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #208 on: November 15, 2014, 09:58:14 pm »
My trigger offset jitter problem no changing by offset value. 5,10,15,20,25us... always there, and same.

What was your signal source?  If the source has that much long period jitter anyway, then the oscilloscope is just going to show that.
 

Offline HexfeT

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #209 on: November 15, 2014, 10:17:13 pm »
I don't have a signal generator. Source is STM32F4 Discovery kit. Using PWM module. 84Mhz bus clock from mcu's pll, PWM module configured bus frequency/4, %50 duty.
 

Offline frogmaster

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #210 on: November 15, 2014, 10:34:21 pm »
Sorry, I'm helpless with English translation in Youtube editor... Takes too much time. |O
I hope, it will be clear without translation. :palm:

Thanks for the vid. I tried to translate it on the fly. My Russian is rather crusty and my English is rather freestyle (and I'm not becoming interpreter, that's for sure  :phew:). Can't comment on the vid, so I hope I can dump it here.

Code: [Select]
Hi all,

not long ago

the widely known video blogger Dave Jones from Australia (not Austria),
who runs the EEVBlog site corresponding channel on youtube site
recorded a problem with devices Rigol DS1000Z and DS2000(A)
the issue specifically concerns its 'synchronization systems' {trigger}
I don't have the (1000) device here now, I got it (lend)

but, as you can see, I do have the DS2000 so I'll try to make it with this one just as Dave Jones has shown in his video. Aside the DS2000, I temporarily have the DS4000 which is a bit more expensive than the DS2000. Let's see if the DS4000 has some similar problem or not.

About the Version: [version info]

Dave named three main problems:
    1. when DC coupling
        jitter occurring at multiples of 5us
    2. when AC coupling
        1. synchro point drifts away
        2. jitter independent of signal frequency and/or form
    3. --

I don't have a signal gen at hand- but I do have an ATmega and I can, independently of the quality of the mega-generated signal, demonstrate the very same problems Dave has shown.

[demo of problems follows]

    1. confirmed
        5us problem -> jitter 10ns
        10us: jitter should disappear now, but I can still see it, so I conclude that the (ATmega) signal is simply not fancy enough. (Thus, I can neither confirm nor ...)
    2. with DC coupling we can nicely see the signal,
    now turning on AC coupling we can't see anything. let's zoom out. we should now see the edge in the center of the screen, what we do see a fairly big misalignment here  (->incorrect)

[citing rigol forum response]

I personally never used the AC coupling (and can't really imagine {think of a way} using it). Otherwise the scope works reasonably well and if it wasn't for Dave wouldn't have noticed that problem.

    3. Can't observe the problem Dave had. I could imagine that Dave's signal somehow interfered with the holdoff value. E.g. If I change my holdoff value here, I can reconstruct a similar 'situation'. But it doesn't say anything about the proper working of the scope.

[describing how the edge falls into the 'holdoff time']

Thus I can conclude that this 'problem' is not a problem with the scope but a problem with the particular setup {the way its user set up the scope}.

[around 13min]

Trying to reproduce the problems Dave describes I found another problem. Given this specific device that supports external triggering. I'm triggering *the same signal* over the EXT trigger. Firstly, we observe an offset of 10ns. The real signal's pk-pk value is 5V, so considering the fact that the probe is x10 the center is around 2.5V [seeing 254mV]. As soon we're moving the trigger value below 0 {below the signal}, sync breaks down (trigger goes beserk). As soon we're above 440mV {i.e. above 5V}, same thing.

Now let's change to AC trigger. Nothing changed. So there's no way of really triggering AC-style. (There's no AC trigger function.) Rigol could've just left that option out.

[summing up stuff]

[same procedure, 4 problem checks on the DS4024]
 

Offline JDubU

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #211 on: November 16, 2014, 01:20:30 am »
DS2072 (not A version)
HW version: 2.0
Firmware: 00.03.01.00.04 (latest available)

Signal Source:  Epson SG-615P 7.3728MHz 100ppm crystal oscillator module.

Multiple of 5us delay issue:  No visible jitter at all for any delay
AC trigger issue:  Approx. 8ns jitter

Note:  I first tried using a 2.5MHz PWM timer output from a STMF4 Discovery board as a signal source but that signal had a consistent 25ns jitter.
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #212 on: November 16, 2014, 01:57:49 am »
no jitter at 0 delay with any of the four sources
plenty of jitter at sufficient nonzero delay, but ONLY with the first two function generators
no jitter at sufficient nonzero delay with the two RF ovenized synthesizers

Function generators usually have high long period jitter so this is not unexpected.

Quote
Now, all the non-Rigol scopes use equivalent time sampling and it seems clear that in the absence of a stable source, such as the synthesizers, the combination of sampling and delay leaves one with a "jittered" presentation after the wandering waveform builds up.

Variable persistence or envelope mode can be used with equivalent time sampling to show the jitter.

Quote
Apparently, the Rigol is doing some analog of equivalent time sampling (???) since I get exactly the same behavior - OK only with the synthesizer sources.

They have to do something to get better than 4ns timing resolution at 250MS/s.  I think they measure the trigger to sample time after interpolation which can be done in FPGA logic.  This is just another way to do equivalent time sampling with a digital trigger.

Quote
Incidentally, the Tek scope passes the test because it cheats - it won't let you set the delay large enough to cause a problem.

I could not find much on the TDS350 but it looks like a striped down TDS460.

Quote
Anyway, I feel a lot better now knowing that my 1980-1990 scopes are just as good as my 2014 scope!

The difference is your 1980-1990 oscilloscopes cost 20 times more.
 

Offline HexfeT

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #213 on: November 16, 2014, 03:12:49 am »
My trigger offset jitter problem no changing by offset value. 5,10,15,20,25us... always there, and same.

What was your signal source?  If the source has that much long period jitter anyway, then the oscilloscope is just going to show that.

Ok, i understand now, signal source stability is very important. I found a crystal oscillator and test again. Results are good now.

DS1054Z
SW: 00.04.01.SP2
HW: 0.1.1
 

Offline Matthias Toussaint

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #214 on: November 16, 2014, 10:18:12 am »
I know there's been little to no discussion of the dual-slope triggering "bug" mentioned in the video, but I just wanted to point out that this is not a bug at all, rather an artefact caused by trigger holdoff working correctly.

So I put together a quick little video explaining how trigger holdoff causes the observed behaviour -- and I also show how holdoff (even the default, minimum setting) could cause real confusion even if you're using normal edge triggering. This is not Rigol specific, this applies to any scope (with a trigger). With the DS2202 @ factory default settings, these problems could potentially (in admittedly somewhat contrived circumstances) bite you at frequencies as low as 5 MHz.



Why do the DS1000Z and DS2202 behave differently in the EEVBlog video? Because the default(=minimum) holdoff of the DS1000Z, 16ns, is less than the 100ns of the DS2202. 16ns fits inside a 20 MHz pulse (25 ns), 100ns does not. Neither is right nor wrong, and both can be configured to behave as desired.

I made a quick test with a DS4054 and the effect can not be observed there. Dual slope trigger is stable and does not change with holdoff. I believe your explanation is correct, I'm just wondering how they made it work on the DS4000.

BTW: I also can't see AC coupling problems on my scope

http://youtu.be/Z6i9-pQ-kNk
 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #215 on: November 16, 2014, 12:09:05 pm »

I made a quick test with a DS4054 and the effect can not be observed there. Dual slope trigger is stable and does not change with holdoff. I believe your explanation is correct, I'm just wondering how they made it work on the DS4000.

BTW: I also can't see AC coupling problems on my scope

http://youtu.be/Z6i9-pQ-kNk

Your video is marked private, so we can't watch!

If your talking about the delay jitter, I found it on my 4000:

MSO4054 at various delays and beyond, sorry for the ultra crappy webcam footage.  (firmware = 2.02.SP1, hardware version = 1.3)

20Mhz, square, 5Vpp, AC/DC coupling has no effect.



Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #216 on: November 16, 2014, 12:43:52 pm »
If your talking about the delay jitter, I found it on my 4000:

MSO4054 at various delays and beyond, sorry for the ultra crappy webcam footage.  (firmware = 2.02.SP1, hardware version = 1.3)

20Mhz, square, 5Vpp, AC/DC coupling has no effect.


This looks like a different problem then the one Dave documented.  The jitter is roughly equal at 1us of delay and longer instead of vanishing at 10us; long period jitter does not appear to increase until much higher delays.

What was the signal source?  This is the kind of result I might expect when using a dithered 1 GS/s DDS to produce square waves.
 

Offline Marc M.

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #217 on: November 16, 2014, 01:16:11 pm »
....What was the signal source?
 Did you try making small variations to the frequency?
I don't think anybody gave you a direct answer when you asked about this earlier. If they did, I apologize for being redundant.  I used a Rigol DG4162 set to a 15 MHz sine wave, 3Vpp, 0V offset and got the same behavior on my Rigol DS2072 with the trigger set to AC coupling.  I then varied the frequency by Hz, 10's of Hz, 100's, etc. up a couple of MHz.  Other than changing the pattern of the displayed jitter, it had no effect on the amount of jitter.  As a second source I used the RF output of a Rohde & Schwarz CMU-200 Univ. Radio Tester clocked by an external rubidium standard.  I tried 10, 13, 15, 16, 19, & 20 MHz and all exhibited the same behavior so I don't believe it's frequency dependent.  Like others, setting low freq. rejection reduced the amount of jitter by about 1/2 or so but didn't eliminate it.
Don't replace the cap, just empty the filter!
 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #218 on: November 16, 2014, 01:19:30 pm »

What was the signal source?  This is the kind of result I might expect when using a dithered 1 GS/s DDS to produce square waves.

In the video above it's a DG4000, but I replicated the jitter with a 20Mhz OCXO as well. 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #219 on: November 16, 2014, 03:20:59 pm »
Playing around some more.  Notice how memory depth/averaging change the artifact behaviour.

Also notice when scope is stopped, horizontal position changed, the artifacts disappear.

(MSO4054, random 16Mhz TCXO, DC trigger coupling, 100us delay is roughly the worst point, does not disappear every 5us like Dave's, self cal last night - think Rigol mentioned doing this)


Offline open loop

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #220 on: November 16, 2014, 04:09:48 pm »
Have read about 70% of all the posts so apologise for mentioning anything that has already been discussed. Couple of ideas...

Could it be anything to do with the intensity graded display, what happens when the intensity graded display is switched off? I know it sounds unrelated but you never know  :-//

Another thing to try for the 5us issue is to feed the same signal into channels 1 and 2 then trigger off channel 2 experiment with the coupling on this channel and see if it possible to do AC trigger either using channel 2 AC signal coupling or AC trigger coupling...

Interesting to note that the AC Trigger coupling issue was never really noticed for two years on the well loved Rigol 2000 series.  As there is an option for AC trigger coupling I would have thought that Rigol would have a test case for it.  It just goes to show that scopes are getting so complicated that even the manufacturers are missing things. I bet even the Agilent/Tektronix have bugs in the "Fringe" capabilities of their scopes.  :-BROKE

I am seriously considering upgrading my DS1052E to a DS1000z series and this has not really changed my mind as I have never used AC coupling on triggering before. I would be very happy with a new ds1000z series, a lot of scope for the price and it seems that Rigol are keen to address issues when they come up. Fortunately the Rigol distributer is 20mins drive from my home  :box:


 

Offline iDandelions

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #221 on: November 16, 2014, 04:21:49 pm »
I've just been messing around with the in-built calibration signal on my MSO2072A as I don't have a sig gen. I was looking at the seemingly random ability of the scope to trigger on both rising and falling slopes. I noticed that switching the display type between vectors and dots alters the result of the trigger. It doesn't always do it, but I'm surprised it affects the trigger.

https://www.dropbox.com/s/vltg0dmwr2fc5kw/MSO2072A_20141116-160429.png?dl=0

https://www.dropbox.com/s/09q1wkh4ndxif66/MSO2072A_20141116-160445.png?dl=0

(added screen shots as links as I can't get the img tag to work)
« Last Edit: November 16, 2014, 06:40:18 pm by iDandelions »
 

Offline electronic_eel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #222 on: November 16, 2014, 04:22:03 pm »
Playing around some more.  Notice how memory depth/averaging change the artifact behaviour.

Also notice when scope is stopped, horizontal position changed, the artifacts disappear.

(MSO4054, random 16Mhz TCXO, DC trigger coupling, 100us delay is roughly the worst point, does not disappear every 5us like Dave's, self cal last night - think Rigol mentioned doing this)
Do you have a 10MHz reference available? Would you mind testing it again with an external 10 MHz?
 

Offline dr.diesel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #223 on: November 16, 2014, 04:46:10 pm »
Playing around some more.  Notice how memory depth/averaging change the artifact behaviour.

Also notice when scope is stopped, horizontal position changed, the artifacts disappear.

(MSO4054, random 16Mhz TCXO, DC trigger coupling, 100us delay is roughly the worst point, does not disappear every 5us like Dave's, self cal last night - think Rigol mentioned doing this)
Do you have a 10MHz reference available? Would you mind testing it again with an external 10 MHz?

No problem, 10Mhz OCXO:


Offline electronic_eel

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #224 on: November 16, 2014, 04:52:01 pm »
No problem, 10Mhz OCXO:
thank you. but it seems I wasn't clear enough:

Please feed the 10 MHz from the OCXO into the external reference input on the back of the scope. You then have to select Reference Clock Input in the utilty menu.
Then measure e.g. the same 16 MHz TCXO from the video before.

This way we can see if the reason for the jitter is jitter from the internal oscillator of the scope.
« Last Edit: November 16, 2014, 04:55:07 pm by electronic_eel »
 


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