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REVIEW - Rigol MSO5000. Tests, bugs, questions

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vicki20july:
 :-+

2N3055:

--- Quote from: Fungus on September 05, 2022, 09:42:04 am ---
--- Quote from: vicki20july on September 05, 2022, 02:24:13 am ---

--- Quote from: Fungus on September 05, 2022, 01:09:47 am ---
You can use the extra sample rate on the Rigol reduce noise by oversampling. This is a new feature added in a firmware update (it happens!) so it makes all older threads that discuss noise less valid.


--- End quote ---

Thank you all for the replies. Just wondering, Fungus is it there any video showing this functionality / improvement or is it documented anywhere. Is it a respectable improvement.

--- End quote ---

It's called "high res" mode.




nb. The video also shows also color grading mode which can use "averaging" mode to highlight the true signal inside the noise by averaging various waveforms together.

If you mess around using the two techniques you can probably find what you're looking for.

Siglent owners will counter that they don't need to "mess around", which is true. Again: It all comes  down to what you're going to be using your 'scope for. FUD is an easy thing to spread here.

Difference between high res and averaging:



--- End quote ---

C'mon Fungus, we had lengthy discussions (plural) about that first Rigol video and Hires mode in general.

First, that first video from Rigol is wrong and misleading. They abused fact that Rigol MSO5000 has better overdrive recovery than RTB2000 (which is a shame they didn't point that out because it is very important parameter), but choose to fake less noise by using that. Also it is pointless anyways, because despite better recovery it still distorts signal so it is not to be trusted anyways.  Also it is misleading (and wrong) changing vertical sensitivity and offset and call that "zoom". Zoom is just that: graphic zoom on the screen without messing with input channel settings, but that is not so useful for 8 bit scopes as for scopes with higher resolution.

As for Hires, it IS NOT replacement, fix, or solution for high noise in input channel of the scope. Hires uses filter that filters high frequencies out. That way it filters out noise energy in those high frequencies, leaving just low frequency noise. Which makes residual noise smaller and only fraction of full range noise.It does that by using Hires to make a 350 MHz scope a 50Mhz or 20Mhz or 500kHz scope, depending on how much bits of Hires you apply. If you only do audio range, that might not matter to you. For everything else it is a problem. Because of this it is very important that user have control of how much Hires is applied, because that defines lowpass filtering effect.

That is one problem. Other is: other scopes, including ones with much better frontends, have their own version of Hires..
And some scopes have less noise than MSO5000 with Hires, even when working full range 500MHz. Just think how low noise those get when you apply Hires on those...

A note: we also had many (some heated) discussions of how important the scope noise is in general. A short version is that it is very important if you work on devices that need low noise measurements. If you only work on stuff that is digital level and you generally only need to look at general waveforms etc, it might not be important. It is up to user and user's work. But if low noise measurements are needed, there is no trick or fix to an noisy instrument.  Only solution is a low noise instrument (scope).

Just making facts straight.

Best,

Fungus:

--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---C'mon Fungus, we had lengthy discussions (plural) about that first Rigol video and Hires mode in general.

First, that first video from Rigol is wrong and misleading. They abused fact that Rigol MSO5000 has better overdrive recovery than RTB2000 (which is a shame they didn't point that out because it is very important parameter), but choose to fake less noise by using that. Also it is pointless anyways, because despite better recovery it still distorts signal so it is not to be trusted anyways.

--- End quote ---

I didn't post if because of that. I posted it because there's a clear moment where hires mode is turned on and yu see the difference. The color mode is also interesting/useful and it's shown clearly.


--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---As for Hires, it IS NOT replacement, fix, or solution for high noise in input channel of the scope.

--- End quote ---

I specifically said that it wasn't, but it does help.


--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---Hires uses filter that filters high frequencies out. That way it filters out noise energy in those high frequencies, leaving just low frequency noise. Which makes residual noise smaller and only fraction of full range noise. It does that by using Hires to make a 350 MHz scope a 50Mhz or 20Mhz or 500kHz scope, depending on how much bits of Hires you apply.

--- End quote ---

Huh? If you're sampling at 8GHz then you have multiple samples within each 350MHz time period. Averaging them won't make the bandwidth less then 350Mhz, it simply reduces the noise inherent in the ADC process.

Fungus:

--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---.... using Hires to make a 350 MHz scope a 50Mhz or 20Mhz or 500kHz scope, depending on how much bits of Hires you apply.

--- End quote ---

In practical terms: That's what you're supposed to do. Whenever you're measuring power supply ripple (or whatever) you're supposed to use 1x probes and limit the bandwidth to 20Mhz.

Speaking of practicality; There's also the fact that looking at 350Mhz signals is something you only do with 50 Ohm cables, etc. If you're poking at circuits with probes then it simply isn't going to happen, you'll be lucky to be seeing anything over 100Mhz. 16x oversampling with pokey probes is probably going to show you something a lot closer to the truth than leaving it at full bandwidth.

So again, the "depends on how you're planning to use it" clause comes into play. I'm not doubting the noise is better on a Siglent, I'm pointing out that in practical terms, it's not as big a deal as it might sound.

(Yes, you have to fiddle around optimizing the amount of samples...but most people will only do it on edge cases, not all the time)

2N3055:

--- Quote from: Fungus on September 05, 2022, 12:56:16 pm ---
--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---C'mon Fungus, we had lengthy discussions (plural) about that first Rigol video and Hires mode in general.

First, that first video from Rigol is wrong and misleading. They abused fact that Rigol MSO5000 has better overdrive recovery than RTB2000 (which is a shame they didn't point that out because it is very important parameter), but choose to fake less noise by using that. Also it is pointless anyways, because despite better recovery it still distorts signal so it is not to be trusted anyways.

--- End quote ---

I didn't post if because of that. I posted it because there's a clear moment where hires mode is turned on and yu see the difference. The color mode is also interesting/useful and it's shown clearly.


--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---As for Hires, it IS NOT replacement, fix, or solution for high noise in input channel of the scope.

--- End quote ---

I specifically said that it wasn't, but it does help.


--- Quote from: 2N3055 on September 05, 2022, 12:02:01 pm ---Hires uses filter that filters high frequencies out. That way it filters out noise energy in those high frequencies, leaving just low frequency noise. Which makes residual noise smaller and only fraction of full range noise. It does that by using Hires to make a 350 MHz scope a 50Mhz or 20Mhz or 500kHz scope, depending on how much bits of Hires you apply.

--- End quote ---

Huh? If you're sampling at 8GHz then you have multiple samples within each 350MHz time period. Averaging them won't make the bandwidth less then 350Mhz, it simply reduces the noise inherent in the ADC process.

--- End quote ---

Hires is not averaging. Averaging is useful only for repetitive, low phase noise (low jitter) signals.
Hires is lowpass filtering.

Single channel calculations (for 2 ch divide by2, for 3 and 4 channels divide by 4)
For 1 bit improvement BW is 0,238 (1/4) of original Nyquist (8GS sample rate, 4GHz Nyquist  effective 1GHz 1 h/250MHz 4ch).
For 2 bit improvement BW is 0,0625 (1/16) of original Nyquist (8GS sample rate, 4GHz Nyquist  effective 250MHz 1ch/62.5MHz 4ch).

2 bit improvement is roughly what MSO5000 need to show similar RMS of noise to RTB2000 or SDS2000X+.

For 3 bit improvement BW is 0,0625 (1/64) of original Nyquist (8GS sample rate, 4GHz Nyquist  effective 15.625MHz 1ch/3,9MHz 4ch).

So you could say that 1 bit improvement would be transparent , like you say. But not more, and since it has much more noise to begin with, it is not enough.

In practical terms, you DO NOT filter signal unless you want to do that deliberately because you only want to look at partial signal. Or shall I say, I was always missing MORE bandwidth not less.
Or I could just say your are right. It doesn't matter, and we should all just stop using any scopes with more than 20 MHz BW because it is all just some unwanted interference we don't care about anyways.
And I'm fine with your characterisation that if run lowpass filtered it is a fine normal noise scope. Except Rigol should be selling it as a 50 or 20 MHz scope because that how it's going to get used.

MSO5000 is good scope for the price. It has a noisy front end, but has many features that make it useful instrument. That is despite the fact that is a bit noisy, not because noise is irrelevant. It is not unusable, but its noise figures are not good. If that is important for user, then it is.
Like I said.
I know you are trying to simplify it for a beginner, but you can't. One of the biggest problems of the beginners is not lack of answers but a lack of good questions. They simply cannot formulate their needs because they don't have enough data and knowledge.

That is why, for beginners, I tend to recommend some of the simpler, cheaper scopes. Today's entry level scopes like the SDS1104X-E or equivalents can carry a beginner for many years. Heck, they can do for a professional for most routine tasks... After many years, if they keep the hobby, they will know where to go from there... They are also easier to learn how to use, where we see that even professionals coming from CRT analog scopes need quite some time to learn how to use digital scope to its full extent.



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