Author Topic: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems  (Read 409796 times)

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Offline jkrichards

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #400 on: November 21, 2014, 04:33:36 pm »
UPDATE FROM RIGOL

Short and not explanatory, but:

Quote
1: We have reproduced the two issues in R&D side;
2: All issues can be fixed by firmware updating without deleting any feature;
3: The trail firmware form R&D will be released in early next week, that can be used for Dave or some urgent cases.

This update must be false as I received an email from them this AM stating:

 "Ok. Excellent. Thank you very much for the video.

We haven't been able to reproduce the issue on units that we have here.

Would you be willing to be without the scope for a week or so?

We would like to ask if you could ship the scope to us (we will send you a FedEx label.. just need you to box it up and ship it) for further testing?

We will test it with beta firmware revisions and then ship it back once we have a solid fix in place.

WRT the 30 day return.. we are extending it until we get the fix from Engineering.. so, no risk from that standpoint."
 

Offline Monkeh

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #401 on: November 21, 2014, 04:38:17 pm »
UPDATE FROM RIGOL

Short and not explanatory, but:

Quote
1: We have reproduced the two issues in R&D side;
2: All issues can be fixed by firmware updating without deleting any feature;
3: The trail firmware form R&D will be released in early next week, that can be used for Dave or some urgent cases.

This update must be false as I received an email from them this AM stating:

 "Ok. Excellent. Thank you very much for the video.

We haven't been able to reproduce the issue on units that we have here.

Would you be willing to be without the scope for a week or so?

We would like to ask if you could ship the scope to us (we will send you a FedEx label.. just need you to box it up and ship it) for further testing?

We will test it with beta firmware revisions and then ship it back once we have a solid fix in place.

WRT the 30 day return.. we are extending it until we get the fix from Engineering.. so, no risk from that standpoint."

Alternatively, the person who emailed you was not informed..
 

Offline TMM

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #402 on: November 21, 2014, 04:45:42 pm »
You can only achieve increased resolution if there exists 1LSB (or more) of Gaussian noise on the signal. If the signal is not sufficiently 'noisy' within the window of the averaging filter, it won't work properly.

According to who? I posted a paper that clearly documents both the mathematical method and effect of successive sample averaging - which, BTW, doesn't mention anywhere "adding 1LSB of noise" - but you've not posted any substantiating material.

From the paper that you posted:
Quote from: 'the paper'
Resolution will
always be improved on those portions of a signal that slew
through multiple code counts between samples, but steady-state
signals will see improvement only if there is noise present with
amplitude greater than 1 or 2 ADC LSBs.
Obviously if the size of the window of the filter is small with respect to the input signal transitioning through LSBs of the ADC, the signal itself will not fit the requirements for increased resolution. Adding 1LSB of noise solves that problem entirely.

You yourself raised concern that the DS1000Z did not have the processing power to use a large enough averaging window...

Quote
Tektronix scopes implement high-res correctly and consistently achieve increased resolution, even for noiseless DC.

Again, I'm afraid you would need to post actual documentation proving your assertions.
Observe the youtube video i linked in Reply #390. It is obvious that there is FAR more than 8 bits of resolution on the display as there is no significant pixelation visible even though the signals are scaled to only a small fraction of the vertical span on the display. Doing the same on the DS1000Z results in bulk pixelation due to lack of sampling resolution.

The DS1000Z is definitely increasing the effective resolution - but by only 2 or 3 bits - I can see this clearly on the DS1000Z I have.
I'm afraid you would need to post actual documentation proving your assertions.
« Last Edit: November 21, 2014, 04:48:55 pm by TMM »
 

Offline TMM

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #403 on: November 21, 2014, 04:53:25 pm »
Normal mode


'Hi res' mode


There is no obvious increase in resolution to my eyes, in fact i think 'hi res' looks subjectively worse as the averaging removes noise and makes the quantization levels even more obvious.
 

Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #404 on: November 21, 2014, 04:54:29 pm »
The scale of the display does not change but the waveform record is not 8 bits in the case of the TDS series and similar old Tektronix DSOs and does not even match their digitizer resolution.

Yes - the waveform record (or sample memory) - but this is irrelevant to the real-time display of the waveform, only to external post processing.
 

Offline leppie

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #405 on: November 21, 2014, 05:02:55 pm »

With that resolution, how hard would displaying anti-aliased graphics be? I would sacrifice waveform update rate with accuracy.
 

Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #406 on: November 21, 2014, 05:21:24 pm »
From the paper that you posted:
Quote from: 'the paper'
Resolution will always be improved on those portions of a signal that slew through multiple code counts between samples, but steady-state signals will see improvement only if there is noise present with amplitude greater than 1 or 2 ADC LSBs.

I'm afraid:

"...steady-state signals will see improvement only if there is noise present with amplitude greater than 1 or 2 ADC LSBs"

...is quite different from your statement that:

"You can only achieve increased resolution if there exists 1LSB (or more) of Gaussian noise on the signal."

Quote
Adding 1LSB of noise solves that problem entirely.

That would be assuming it's a "problem that needs to be solved", rather than a simple case that doesn't fit within the parameters of resolution improvement affected by successive sample averaging.

Quote
Observe the youtube video i linked in Reply #390. It is obvious that there is FAR more than 8 bits of resolution on the display as there is no significant pixelation visible even though the signals are scaled to only a small fraction of the vertical span on the display.

I observed the video - it proves nothing about Tektronix adding 1LSB of noise. Whatever averaging it's doing has to be eventually downsampled for the 400 pixels of vertical resolution. Could you please post some documentation from Tektronix that describes them introducing 1LSB of noise before successive sample averaging? That alone would convince me that they're doing it.
 

Offline Bud

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #407 on: November 21, 2014, 05:32:28 pm »
Guys sorry for jumping in. This thread is for the Jitter problem . Unless i misunderstood , may i suggest the Hi-Res discussion to be moved to a separate topic.
Facebook-free life and Rigol-free shack.
 

Offline TMM

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #408 on: November 21, 2014, 05:37:41 pm »
If the signal already slews through multiple LSBs between samples, either:
a) There is noise present on the signal of interest with multiple-LSB amplitude :-+
b) The resolution limitation is now the time domain instead of vertical resolution. If each sample point moves multiple pixels, the effect of hi-res mode is pretty pointless. Time domain interpolation is now required for a visual resolution increase.

I observed the video - it proves nothing about Tektronix adding 1LSB of noise. Whatever averaging it's doing has to be eventually downsampled for the 400 pixels of vertical resolution. Could you please post some documentation from Tektronix that describes them introducing 1LSB of noise before successive sample averaging? That alone would convince me that they're doing it.
Tek inject a 'dither' signal for the spectrum analyzer function of the MDO3000/4000. In their own words (http://www.tek.com/dl/48W-28882-2%20%20%20MDO%20Performance%20WP_.pdf):
Quote from: 'tek'
Dither is a random signal that is added to the input signal to smear its energy across multiple A/D codes, effectively averaging the individual DNL errors across all the codes.
I see no reason they would not use the same function on the MDO3000 when it is in high-res oscilloscope mode. Of course i cannot confirm nor deny that they actually are doing this but it certainly behaves like it does, and the Rigol certainly behaves like it does not. ADCs will introduce some of their own noise when run at their full sample rate, but the gains in resolution by averaging/down-sampling are not nearly as good as when normally distributed analog noise is injected.

Guys sorry for jumping in. This thread is for the Jitter problem . Unless i misunderstood , may i suggest the Hi-Res discussion to be moved to a separate topic.
good idea.

« Last Edit: November 21, 2014, 06:32:08 pm by TMM »
 

Offline eV1Te

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #409 on: November 21, 2014, 06:16:27 pm »
Guys sorry for jumping in. This thread is for the Jitter problem . Unless i misunderstood , may i suggest the Hi-Res discussion to be moved to a separate topic.

I do not think it is to far off topic to mention other bugs to the same instrument, but I will just add my measurements of the Hires bug as a final say to this topic, if anyone else wants to argue that it is not a bug at all, then it might be appropriate to start a new topic regarding this issue.
 
Here are some captures in Normal, Hires and Averaging 256. I stopped the scope at 100 mV vertical, and in stopped mode I increased the vertical to 10 mV (10 times), in order to see the quantization of the bits (you still see it without increasing vertical but it is more clear this way).
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #410 on: November 21, 2014, 06:20:08 pm »
The scale of the display does not change but the waveform record is not 8 bits in the case of the TDS series and similar old Tektronix DSOs and does not even match their digitizer resolution.

Yes - the waveform record (or sample memory) - but this is irrelevant to the real-time display of the waveform, only to external post processing.

The vertical scale on the TDS series has a separate zoom function which operates in real time.  The later pre-TDS series DSOs handle the zoom a little differently but it operates in real time when averaging is used.

Of course no additional resolution is displayed by zoom except when average or higher resolution mode is used to provide it but when that is done, the greater than 8 bit results can be displayed.  On my 2440, saved or real time waveforms will show quantization unless averaging was used during their acquisition and zoom may only be used on real time waveforms when averaging is used.  On a 2230 or 2232, the same applies but zoom only works on saved waveforms.  From what I remember of the TDS series, high resolution mode may be used in place of averaging for this so an acquisition record of greater than 8 bits is created and transferred to the waveform memory.

To sum up the above, the waveform record on these oscilloscopes is greater than 8 bits and may be displayed in real time showing resolutions greater than 8 bits when averaging or high resolution mode is used during acquisition.

I have to defer to you and others about how the Rigol DSOs work in regard to the above.  I did not get around to testing this aspect of their operation when I was evaluating them.  Some of their known quirks like making automatic measurements on the display record imply problems.
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #411 on: November 21, 2014, 06:26:46 pm »
With that resolution, how hard would displaying anti-aliased graphics be? I would sacrifice waveform update rate with accuracy.

It looks to me like an anti-aliased display of an 8 bit waveform.  I assume Rigol used an 8 bit waveform record and processing to preserve the highest possible update rate.
 

Offline Bud

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #412 on: November 21, 2014, 06:54:26 pm »
Guys sorry for jumping in. This thread is for the Jitter problem . Unless i misunderstood , may i suggest the Hi-Res discussion to be moved to a separate topic.

I do not think it is to far off topic to mention other bugs to the same instrument,

Yes fair to say so but a new reader may think that Hi-Res mode has to do with the jitter problem, which it does not...
 
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Offline jkrichards

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #413 on: November 21, 2014, 06:56:02 pm »
UPDATE FROM RIGOL

Short and not explanatory, but:

Quote
1: We have reproduced the two issues in R&D side;
2: All issues can be fixed by firmware updating without deleting any feature;
3: The trail firmware form R&D will be released in early next week, that can be used for Dave or some urgent cases.

This update must be false as I received an email from them this AM stating:

 "Ok. Excellent. Thank you very much for the video.

We haven't been able to reproduce the issue on units that we have here.

Would you be willing to be without the scope for a week or so?

We would like to ask if you could ship the scope to us (we will send you a FedEx label.. just need you to box it up and ship it) for further testing?

We will test it with beta firmware revisions and then ship it back once we have a solid fix in place.

WRT the 30 day return.. we are extending it until we get the fix from Engineering.. so, no risk from that standpoint."

Alternatively, the person who emailed you was not informed..

Should that make us feel better?  I think they will be getting a bunch of them in for testing soon.   
 

Offline David Hess

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #414 on: November 21, 2014, 07:21:07 pm »
Are you kidding me!  I have a hard time believing they have no scope to test with.  They want to use my personal scope for testing???  Seems like a mickey mouse operation.  Lets see... I purchase a new scope so they can do R&D.
I am very disappointed in the way this whole thing has been handled.  This is the last Rigol product I will purchase.

Rigol, Send me one of the working scopes you have. and I will gladly send you this broken one for R&D.  :wtf:

Maybe they outsourced design and production (to whom?) to keep costs low and really do not have any of their own DSOs or test equipment to work with.
 

Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #415 on: November 21, 2014, 07:41:16 pm »
From what I remember of the TDS series, high resolution mode may be used in place of averaging for this so an acquisition record of greater than 8 bits is created and transferred to the waveform memory.

Well, luckily there's this newfangled contraption called The Internet that can supplement memory :)  Unfortunately, after much digging, I can find no documentation that any Tektronix DSO/MSO specifically creates waveform records of greater than 8 bits when using Hi-Res - but perhaps you can dig up some evidence to support this.

Quote
To sum up the above, the waveform record on these oscilloscopes is greater than 8 bits and may be displayed in real time showing resolutions greater than 8 bits when averaging or high resolution mode is used during acquisition.

You are summing up your opinions - which, again, have yet to be supported with any documentation. And while I don't doubt that Tektronix scopes could slice bread if inserted correctly, I'm afraid I would need to see documentation from Tek describing the workings of that feature.

Quote
Some of their known quirks like making automatic measurements on the display record imply problems.

Oh my! You mean exactly like the Agilent X-series and virtually every other low-cost DSO on the market does? Does that mean that ALL of those DSO's have problems?  ;D
 

Offline H.O

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #416 on: November 21, 2014, 07:42:42 pm »
H.O. can you post that same image at T=0?  Does it look better at T=0?

Hi,
Sure. Attached is a montage of 4 different screenshots. T=0, T=5us, T=15us and T=105us. Same 10MHz Square wave from DG4162, 50% dutycycle. Input DC coupled, trigger AC coupled. For reference, this is on a DS4k.

As you can see it does a look a bit better at T=0 and gets progressively worse as T increases (as expected). It's not much of a difference between T=0 and T=15 but it's clearly vissible at T=105us.
 

Offline rf-loop

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #417 on: November 21, 2014, 10:18:32 pm »

Well, luckily there's this newfangled contraption called The Internet that can supplement memory :)  Unfortunately, after much digging, I can find no documentation that any Tektronix DSO/MSO specifically creates waveform records of greater than 8 bits when using Hi-Res

Really? Or is this some kind of joke.

Simple case if people have enough real work working experience with digital scopes.  Peoples in this forum have so different knowledge and specially so different experience with test equipments including also last 30 years digital scopes.

Tektronix many TDS models do it sure. Even my  old TDS520 what is partially retired last years.


In Hi-Res mode it use double amount of capture memory - why? Because in thiss mode it store 2 bytes for one (calculated) data point. (it is 16 bit)
It produce this using averaging (high res mode type of averaging)

In normal mode it store of course 8 bit raw ADC data.

Where are documents?

Of course these are documented in this serie scopes manuals.

And extremely clearly.

Take example TDS series programmers manual (TDS410 up to TDS 784)

Look then example page where is explained command  DATa:WIDth   and also related command CURVe. Perhaps it proofs this enough.

No need more this OT.

If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
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Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #418 on: November 22, 2014, 01:30:06 am »
Take example TDS series programmers manual (TDS410 up to TDS784).

Thank you! I just wanted to be pointed in the direction of relevant documentation and there are a lot of Tek documents and manuals (and TDS models) - so I clearly wasn't finding the correct ones.

But I found a ton of useful information, including, yes, confirmation of their 16-bit waveform records, a detailed description of their Hi Res technique (which certainly does not involve introducing noise or injecting a dither signal), and a chart specifying their downsampling from Hi Res mode to the display graticule on the TDS XXXA series (which seems to be quite similar to the Rigol DS2000, since they both normally map their ADCs to 10 vertical divisions).

Anyway, thanks again for the tip - will refrain from further discussion of Hi Res.
« Last Edit: November 22, 2014, 01:31:53 am by marmad »
 

Offline jkrichards

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #419 on: November 22, 2014, 12:28:06 pm »
2nd email from them this AM in response to the questions document.

"Ok. Excellent. Thank you very much for the video.

We haven't been able to reproduce the issue on units that we have here.

Would you be willing to be without the scope for a week or so?

We would like to ask if you could ship the scope to us (we will send you a FedEx label.. just need you to box it up and ship it) for further testing?

We will test it with beta firmware revisions and then ship it back once we have a solid fix in place.

WRT the 30 day return.. we are extending it until we get the fix from Engineering.. so, no risk from that standpoint"


Are you kidding me!  I have a hard time believing they have no scope to test with.  They want to use my personal scope for testing???  Seems like a mickey mouse operation.  Lets see... I purchase a new scope so they can do R&D.
I am very disappointed in the way this whole thing has been handled.  This is the last Rigol product I will purchase.

Rigol, Send me one of the working scopes you have. and I will gladly send you this broken one for R&D.  :wtf:

Rigol sent another email stating they are going to send a new working scope to exchange the broken one for use to troubleshoot these issues.   :-+ 
Jeff
« Last Edit: November 22, 2014, 04:55:17 pm by jkrichards »
 

Offline i4004

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #420 on: November 22, 2014, 06:26:59 pm »



In Hi-Res mode it use double amount of capture memory - why? Because in thiss mode it store 2 bytes for one (calculated) data point. (it is 16 bit)
It produce this using averaging (high res mode type of averaging)


No need more this OT.

if i now write this in rigol z thread, nobody will read it, but yes, mods should move some of this thread that way:

first, what does averaging have to do with "hires"?
if you ask me, nothing. you still have the same crappy screen resolution.

2nd, graticule of z series is 25pix per div, which yields 300x200 resolutuion (cropped graticule negative down, just zoom and count pixels), and these screens look exactly like that....screenshits. never mind 800x480 screen, it's not even close.

now i'm afraid even to think about 1052 resolution, it's essentially a toy...

scarry really...  :palm:
(yes, 1052 scarier, but z is also very low res)
« Last Edit: November 22, 2014, 06:30:15 pm by i4004 »
 

Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #421 on: November 22, 2014, 06:37:48 pm »
first, what does averaging have to do with "hires"?

As already mentioned: Hi Res = successive sample averaging (i.e. boxcar filtering).

Quote
2nd, graticule of z series is 25pix per div, which yields 300x200 resolutuion (cropped graticule negative down, just zoom and count pixels)

Graticule of Z series = 50px per div / Waveform display area = 12x8 divs = 700x400px

EDIT: Added cropped image from Photoshop - no need to count pixels.

EDIT2: BTW, starting a new thread in a couple of minutes to discuss any/all anomalies/bugs in/between UltraVision models.
« Last Edit: November 22, 2014, 06:58:39 pm by marmad »
 

Offline i4004

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #422 on: November 22, 2014, 06:54:26 pm »
no, count them (you can count them on your image too, it's easier than my image), unlesss there's a display setting i missed, and i doubt it, i searched the display menu last nite esp. because of screens like this (and also because i'm into video on pc, so i recognize lores instantly).

you do see that even though screen res is higher, the only resolution you get in the waveform is the one of graticule, right?
count graticule dots, nothing else. 

i understand what is said about hires mode, ie how it works (ie ...every pixels becomes a merger of surrounding pixels around it) but that has nothing to do with screen resolution in any way...
i would call this false advertising.
hires would mean more pixels, more dots, no matter if you speak about television, or the scope.
more pixels=better.
that's why i sadi this scope whould have hdmi 1080p output.
and a display processor to go with it (not just to output this lores crap via hdmi but to have a true 1080p resolution).
and improved sampling system (better to say vertical resolution of more than freaking 8bits!), if needed...heh

and i think anti-aliasing option in the scope has nothing to do with display, but with acquisition, i'm mentioning this because in video and games the anti-aliasing term means "to remove stair-stepping jaginess".
here i would say it probably limits the input to nyquist or alike (i'm guessing).
(too lazy to check the rigol manual (which lacks the menu tree, btw. the only thing i wanted to see in it, it lacks!) but you'll correct me if i'm wrong....)

edit_x: but just the rigol UI inconsistencies alone need the separate thread!  :-//
« Last Edit: November 22, 2014, 07:04:15 pm by i4004 »
 

Offline i4004

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #423 on: November 22, 2014, 07:08:37 pm »
damn!
i missed every other pixel!
 :palm:

it's like you say.

guess i should watch screenshots from higher distance on pc monitor.  :-DD

edit/ hold on a bit there: vertical resolution is half the one you stated, 200pixels like i originally said, because you have 2 vertical pixels as smallest possible sample....ie 2 vertical pixels are one colour ie one pixel. they align nicely on the right side of the graticule.
« Last Edit: November 22, 2014, 07:15:18 pm by i4004 »
 

Offline marmad

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Re: EEVblog #683 - Rigol DS1000Z & DS2000 Oscilloscope Jitter Problems
« Reply #424 on: November 22, 2014, 07:11:04 pm »
no, count them (you can count them on your image too, it's easier than my image), unlesss there's a display setting i missed, and i doubt it, i searched the display menu last nite esp. because of screens like this (and also because i'm into video on pc, so i recognize lores instantly).

Are you just counting the tick marks on the graticule division lines? Because, if so, that's not the resolution - the resolution of the graticule is ALL screen pixels between two major division lines - in other words, 50 pixels on the UltraVision models (as clearly shown by Photoshops rulers). I can easily post an image showing all of the pixels being used.

EDIT: Whoops - I just saw you posted a correction - so nevermind  :)

Quote
i understand what is said about hires mode, ie how it works (ie ...every pixels becomes a merger of surrounding pixels around it) but that has nothing to do with screen resolution in any way...
i would call this false advertising.

I would agree that it's not the best way to describe the feature - I would prefer that DSOs used "Waveform Average" instead of "Average", and "Sample Average" instead of "Hi Res" - but as mentioned earlier, the name appears to have been invented by Tektronix.

Quote
and i think anti-aliasing option in the scope has nothing to do with display, but with acquisition, i'm mentioning this because in video and games the anti-aliasing term means "to remove stair-stepping jaginess".

This is a whole other problem with the Rigol UltraVision DSOs - but I think we should discuss it at the new thread I'm creating  ;)
 


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