Author Topic: Rigol MSO5000 Artifacts  (Read 4751 times)

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Offline jacekowskiTopic starter

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Rigol MSO5000 Artifacts
« on: January 17, 2022, 04:41:47 pm »
Hi All,

I have recently purchased brand new MSO5104 which exhibits very strange behaviour with CH1 and CH3 enabled at the same time (it also happens with just CH1 but it is less obvious),

Pictures show the problem quite nicely, both channels are fed with the same 120MHz or 130MHz sine wave, however CH1 shows a "spike" or "artifact" happening randomly (can be quite easily detected by setting trigger level so it only just triggers).

My local distributor replaced the scope once with a unit where the issue was almost not noticeable at 120MHz, but it is still there and noticeable at 130MHz.

Has anybody noticed a similar issue on their unit, also, does it happen on higher bandwidth units as well? (i don't want to spend money on upgrading bandwidth to test it on potentially faulty scope and at the same time i don't want to end up with warranty issues if i upgrade it via alternative means).
 
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Offline perdrix

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Re: Rigol MSO5000 Artifacts
« Reply #1 on: January 17, 2022, 05:55:28 pm »
Are you 100% sure that you signal generator is producing totally clean sine waves?

Not saying it isn't but ...

D.
 

Online Fungus

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Re: Rigol MSO5000 Artifacts
« Reply #2 on: January 17, 2022, 06:09:24 pm »
I don't have an explanation, just some observations/questions:

a) It looks to me like a problem with the signal to me. Is it the exact same signal/cable connected to both inputs? What happens if you swap the connections around, does it happen on channel 3?

b) Upgrading the bandwidth for testing is really, really cheap. Just find the MSO5000 hacking thread.

c) Those traces look really thin. I've been assured that Rigol MSO5000s are unusable due to ADC noise so what gives? Anybody...?

« Last Edit: January 17, 2022, 06:11:32 pm by Fungus »
 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #3 on: January 17, 2022, 06:13:59 pm »
Pendrix:
I'm sure signal generator is ok (i'm feeding same signal into both ch1 and ch3 and issue disappears when ch2 or 4 is also enabled).

Fungus:
a) issue stays on ch1
b) i don't want to void my warranty yet
c) single capture so no persistence.
 

Online nctnico

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Re: Rigol MSO5000 Artifacts
« Reply #4 on: January 17, 2022, 06:20:19 pm »
Can you run the self calibration (if possible / present)? If the problem dissapears with more channels enabled, it could be a calibration problem when 2 ADCs are used in parallel. The sine waves also look distorted.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online Fungus

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Re: Rigol MSO5000 Artifacts
« Reply #5 on: January 17, 2022, 06:24:33 pm »
Fungus:
a) issue stays on ch1

It doesn't make sense that it would be only on some peaks and not all of them. What percentage of peaks show this? (approx)

Does it do it at lower frequencies or only when you go past the bandwidth limit?


« Last Edit: January 17, 2022, 06:29:24 pm by Fungus »
 

Online tautech

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Re: Rigol MSO5000 Artifacts
« Reply #6 on: January 17, 2022, 06:44:54 pm »
I don't have an explanation, just some observations/questions:

a) It looks to me like a problem with the signal to me. Is it the exact same signal/cable connected to both inputs? What happens if you swap the connections around, does it happen on channel 3?

b) Upgrading the bandwidth for testing is really, really cheap. Just find the MSO5000 hacking thread.

c) Those traces look really thin. I've been assured that Rigol MSO5000s are unusable due to ADC noise so what gives? Anybody...?
It's in Stop mode Fungus but the trigger point is finding the noise.
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Online 2N3055

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Re: Rigol MSO5000 Artifacts
« Reply #7 on: January 17, 2022, 06:51:40 pm »
Can you run the self calibration (if possible / present)? If the problem dissapears with more channels enabled, it could be a calibration problem when 2 ADCs are used in parallel. The sine waves also look distorted.
This.

Rigol uses parallel overlapped ADCs and this looks exactly like it does when ADCs are not properly calibrated and scaled. Run autocal and check again.
 

Online Fungus

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Re: Rigol MSO5000 Artifacts
« Reply #8 on: January 17, 2022, 06:52:20 pm »
c) Those traces look really thin. I've been assured that Rigol MSO5000s are unusable due to ADC noise so what gives? Anybody...?
It's in Stop mode Fungus but the trigger point is finding the noise.

So it's in averaging mode and the glitch is repeating periodically enough for it to smooth out the signal...?
 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #9 on: January 17, 2022, 06:53:52 pm »
Pictures show the problem quite nicely, both channels are fed with the same 120MHz or 130MHz sine wave, however CH1 shows a "spike" or "artifact" happening randomly (can be quite easily detected by setting trigger level so it only just triggers).

If you are feeding them the exact same signal--by this I would think you mean one channel from the signal generator and a cable with a tee--then how can they be horizontally displaced in the first picture?

Can you specify exactly how the input is set up--type of sig gen, cables, etc, perhaps a photo? 

Is it possible to ever see this issue if you trigger from CH3?  Do the glitches always appear at the trigger point or can you catch it happening on a non-trigger cycle?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Online 2N3055

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Re: Rigol MSO5000 Artifacts
« Reply #10 on: January 17, 2022, 07:19:57 pm »
I forgot to ask:
Do you have cables 50Ohm terminated at the scope side??
 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #11 on: January 17, 2022, 07:24:13 pm »
So it's in averaging mode and the glitch is repeating periodically enough for it to smooth out the signal...?

Presumably this is a single-shot and the trace will only be one sample wide regardless of how much noise there is.  Look at how terrible the sine shape is--if that is due to noise, imagine a large numbers of them with different distortions all laid over one another.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Online Fungus

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Re: Rigol MSO5000 Artifacts
« Reply #12 on: January 17, 2022, 07:57:27 pm »
So it's in averaging mode and the glitch is repeating periodically enough for it to smooth out the signal...?

Presumably this is a single-shot and the trace will only be one sample wide regardless of how much noise there is.  Look at how terrible the sine shape is--if that is due to noise, imagine a large numbers of them with different distortions all laid over one another.

I was looking at the first image. The flat spots at the bottom of the waves should be noisy, right?

But let's not derail the thread with that until we find out what a self-cal does and/or where the glitch is coming from.

If it's only on CH1 then we can suspect the 'scope.

OTOH OP's story of "exact same signal" doesn't add up because as you rightly pointed out there's a big phase difference between the two channels.

 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #13 on: January 17, 2022, 08:10:09 pm »
nctnico: 2N3055:
Calibration does nothing to fix it.

Fungus:
Approximately less than 10% more than 1%.
It does it at lower frequencies but it is a lot harder to trigger on it reliably and find it (and it is a lot less obvious).
Shift was caused by daisy chaining the channels, most other tests were done with them being fed via equal lengths cables from same T (see attached photo).
Also, you will probably not see any significant noise due to the time base and sample rate (it's only 20 samples per division)


bdunham7:
I've been using siglent SDG2122X up to 120MHz and for signals above 120Mhz i've been using HackRF.
I've tried two different setups, with T coming out of signal generator into bnc/coax into 50ohm terminators at scope end (as shown in attached photo) OR generator into BNC/coax into T connected to ch1 (or ch3) and into another BNC/coax to other channel (which caused shift between the channels).
It is possible to catch the glitches without using trigger but it takes longer to find a nice one.

It seems like i might be looking at the same issue as here:
https://www.eevblog.com/forum/testgear/review-rigol-mso5000-tests-bugs-questions/msg3187486/#msg3187486


Also, i have a tektronix mso3054 here that does not show any issues with the signal.
« Last Edit: January 17, 2022, 08:18:57 pm by jacekowski »
 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #14 on: January 17, 2022, 08:31:41 pm »
Can you use the same setup as in the photo, set the trigger at about the zero volt level, offset the channels by 1 division and then let it run in the 'normal' mode and then post a screenshot?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #15 on: January 17, 2022, 08:42:26 pm »
Just adding one more thing here, the glitch happens on the bottom side of the sinewave as well (see attached).

You can see that there is something happening around the bottom of ch1 (yellow) trace, while pink(purple?) has nothing around it.

On the last one i've also enabled colour grading as it seems to make the issue more visible.
 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #16 on: January 17, 2022, 08:46:32 pm »
That looks like noise of some sort to me.  Can you do all three of those again but triggering on CH3?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #17 on: January 17, 2022, 08:52:42 pm »
Triggering from CH3.
 

Online nctnico

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Re: Rigol MSO5000 Artifacts
« Reply #18 on: January 17, 2022, 09:20:20 pm »
nctnico: 2N3055:
Calibration does nothing to fix it.

Also, i have a tektronix mso3054 here that does not show any issues with the signal.
As a last ditch effort I'd try to swap the cables and use 50 Ohm in line terminators. However if a different DSO shows the signal correctly (using single shot acquisition without averaging / persistence enabled), then I think it is time to return the Rigol MSO5000 and ask for a refund.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #19 on: January 17, 2022, 09:23:25 pm »
 Your setup looks good and I think you said you physically swapped the connectors at the scope and the problem stays with CH1. It just looks like CH1 is noisy or has some strange distortion or reaction to the input signal.  Was the first scope also noisy on CH1 and was it more or less than this?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #20 on: January 17, 2022, 09:32:20 pm »
nctnico:
I'm already using 50Ohm terminators but those don't do anything to the issue.

bdunham7:
1st scope was slightly worse than 2nd one.

 

Offline bdunham7

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Re: Rigol MSO5000 Artifacts
« Reply #21 on: January 17, 2022, 09:43:54 pm »
The only thing that seems a bit baffling is why it goes away when you select CH2 or CH4.  I wonder if the 'noise' might be an instability in the ADC timing, as others previously referred to when the asked you to autocal the scope.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Online nctnico

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Re: Rigol MSO5000 Artifacts
« Reply #22 on: January 17, 2022, 09:47:51 pm »
The only thing that seems a bit baffling is why it goes away when you select CH2 or CH4.  I wonder if the 'noise' might be an instability in the ADC timing, as others previously referred to when the asked you to autocal the scope.
Or the path between the two ADCs is picking up noise. I can imagine that there is a path (PCB trace) that brings the signal from channel 1 to the ADC of channel 2. If that is routed badly, then it could pick up noise.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline jacekowskiTopic starter

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Re: Rigol MSO5000 Artifacts
« Reply #23 on: January 17, 2022, 09:58:39 pm »
nctnico:
On the first scope i've managed to catch something that looks like maybe the samples from ADCs are arriving out of order. Maybe it is still the same thing, but interpolation is somehow making it appear a lot worse.
 

Online nctnico

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Re: Rigol MSO5000 Artifacts
« Reply #24 on: January 17, 2022, 10:08:38 pm »
This looks more like the samples are not aligned in time properly. I notice you are using vector mode which is a linear interpolation method; it basically connects the dots with straight lines so I don't expect any interpolation artefacts to occur. But the image above shows a slightly different effect than when 2 channels are enabled; then you also see peaks beyond the signal amplitude. Typically a self calibration cycle should fix these kind of issues. If not then something is severely broken.
« Last Edit: January 17, 2022, 10:10:37 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 


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