Author Topic: DS1054Z distortion issue?  (Read 17427 times)

0 Members and 1 Guest are viewing this topic.

Online Fungus

  • Super Contributor
  • ***
  • Posts: 9961
  • Country: 00
Re: DS1054Z distortion issue?
« Reply #25 on: April 27, 2016, 06:51:02 pm »
- the square waves are ok down to 244 mV. Below that distortions start to begin, become strong from 100 mV

Screenshots?  :popcorn:

Now it seems it is there with square waves, lesson learned, but I am still not impressed.

I've been reading: http://www.analogzoo.com/2014/12/op-amp-recovery-and-slew-rates/
 

Offline pxl

  • Regular Contributor
  • *
  • Posts: 126
  • Country: hu
Re: DS1054Z distortion issue?
« Reply #26 on: April 27, 2016, 07:08:04 pm »
- the square waves are ok down to 244 mV. Below that distortions start to begin, become strong from 100 mV
Screenshots?  :popcorn:

« Last Edit: April 27, 2016, 07:11:32 pm by pxl »
 

Online tautech

  • Super Contributor
  • ***
  • Posts: 15954
  • Country: nz
  • Taupaki Technologies Ltd. NZ Siglent Distributor
    • Taupaki Technologies Ltd.
Re: DS1054Z distortion issue?
« Reply #27 on: April 27, 2016, 07:13:46 pm »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?
Avid Rabid Hobbyist
 

Offline pxl

  • Regular Contributor
  • *
  • Posts: 126
  • Country: hu
Re: DS1054Z distortion issue?
« Reply #28 on: April 27, 2016, 07:18:36 pm »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?

E.g: checking a 10 V zero crossing glitch on a 300 Vpp signal (with a 1:10 probe).
« Last Edit: April 27, 2016, 07:20:14 pm by pxl »
 

Online tautech

  • Super Contributor
  • ***
  • Posts: 15954
  • Country: nz
  • Taupaki Technologies Ltd. NZ Siglent Distributor
    • Taupaki Technologies Ltd.
Re: DS1054Z distortion issue?
« Reply #29 on: April 27, 2016, 07:54:47 pm »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?

E.g: checking a 10 V zero crossing glitch on a 300 Vpp signal (with a 1:10 probe).
Really  :o Nah, there's gotta be a better method than having the scope free-run and the vertical over-driven like that.

More attenuation, set trigger appropriately, capture the waveform of interest THEN magnify with increased sensitivity.

Make the power of a DSO work for you.  ;)
Avid Rabid Hobbyist
 

Offline pxl

  • Regular Contributor
  • *
  • Posts: 126
  • Country: hu
Re: DS1054Z distortion issue?
« Reply #30 on: April 27, 2016, 08:09:24 pm »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?

E.g: checking a 10 V zero crossing glitch on a 300 Vpp signal (with a 1:10 probe).
Really  :o Nah, there's gotta be a better method than having the scope free-run and the vertical over-driven like that.

More attenuation, set trigger appropriately, capture the waveform of interest THEN magnify with increased sensitivity.

Make the power of a DSO work for you.  ;)

Yes, I can do that with HiRes mode, but what do you magnify with a common 8 bit scope :P
But the problem is, that meanwhile I checking the waveform I have to tune the circuit, so I can't stop-zoom-in-zoom-out-start in an infinite loop. With slow sine waves, however, no problem at all.
 

Online Fungus

  • Super Contributor
  • ***
  • Posts: 9961
  • Country: 00
Re: DS1054Z distortion issue?
« Reply #31 on: April 27, 2016, 08:23:32 pm »
More attenuation, set trigger appropriately, capture the waveform of interest THEN magnify with increased sensitivity.

Make the power of a DSO work for you.  ;)

Yes, I can do that with HiRes mode

What about the "virtual screen" mode (as seen in Dave's video at 11min 02s):



Is Dave just a klutz at a trade show or can it actually give more vertical information?
« Last Edit: April 27, 2016, 08:28:04 pm by Fungus »
 

Offline pxl

  • Regular Contributor
  • *
  • Posts: 126
  • Country: hu
Re: DS1054Z distortion issue?
« Reply #32 on: April 27, 2016, 09:02:49 pm »
It just extends the screen to 6+14 divs, which is mainly targeted for digital channels (and it is also good to reach the hidden +/-1 divs), but the analog channels will clip in about 10 divs. So you won't have 20 div in HiRes mode.
 

Online tggzzz

  • Super Contributor
  • ***
  • Posts: 9855
  • Country: gb
    • Having fun doing more, with less
Re: DS1054Z distortion issue?
« Reply #33 on: April 27, 2016, 09:41:36 pm »
In ALL cases except the one below the result is because of user error.
Until you know how to use a DSO correctly I suggest you use Autoset to get waveforms to be displayed correctly.
Uhmm, pardon? I am the only one who thinks that these results and distorted waveforms are just unacceptable by any means?
Yes  >:D Even high end (>$20k) oscilloscopes will show this behaviour although these usually have more range in their analogue circuitry and faster overdrive recovery.

I would expect to
- specify this behavior
- to detect this phenomenon in the scope (or just measure the input Vpp) and show a GIGANTIC sign to the user, that they can expect Santa and Rudolf instead of proper waveforms.  :-X

It is unreasonable to expect that manufacturers can specify all ways in which an instrument can mislead the unwary. It is reasonable to expect that users are suitably wary and double-check what they think they are seeing. Yes, that means skill and understanding is required; deal with it.

If you have a way of reliably detecting that form of misuse while not giving many false positives, then patent it and sell it to the manufacturers. Hint: it is a very difficult problem, and I very much doubt that you will find a solution.

Overall it is best to rely that a competent user will exercise skill, wariness, humility, and understanding. The user should not be "wrapped in cotton wool".
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline alsetalokin4017

  • Super Contributor
  • ***
  • Posts: 1878
  • Country: us
Re: DS1054Z distortion issue?
« Reply #34 on: April 28, 2016, 12:47:42 am »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?

E.g: checking a 10 V zero crossing glitch on a 300 Vpp signal (with a 1:10 probe).
Really  :o Nah, there's gotta be a better method than having the scope free-run and the vertical over-driven like that.

More attenuation, set trigger appropriately, capture the waveform of interest THEN magnify with increased sensitivity.

Make the power of a DSO work for you.  ;)

This. ^

At what point do you start damaging the vertical amplifiers and/or attenuators?

I can just imagine the conversation:
Customer: One channel doesn't work right any more.
CS rep: When did you first notice this?
Customer: When I applied a 30V p-p signal and I had the V/div set at 10 mV/div.
CS rep:   :palm:
The easiest person to fool is yourself. -- Richard Feynman
 

Online borjam

  • Supporter
  • ****
  • Posts: 738
  • Country: es
  • EA2EKH
Re: DS1054Z distortion issue?
« Reply #35 on: April 28, 2016, 07:29:46 am »
Anyway, it would be a good idea to have a sticky thread with a pointer to some DSO tutorials. At least the three sisters have produced excellent tutorials available for free ;)
 

Online tautech

  • Super Contributor
  • ***
  • Posts: 15954
  • Country: nz
  • Taupaki Technologies Ltd. NZ Siglent Distributor
    • Taupaki Technologies Ltd.
Re: DS1054Z distortion issue?
« Reply #36 on: April 28, 2016, 08:00:24 am »
Anyway, it would be a good idea to have a sticky thread with a pointer to some DSO tutorials. At least the three sisters have produced excellent tutorials available for free ;)
There's a few in this sticky in the Beginners board, I thought they were mostly CRO's but Alan (w2aew)does have a few using DSO's if you have a hunt.  ;)

https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/

Heaps of links to good reference material too.
Avid Rabid Hobbyist
 

Online Fungus

  • Super Contributor
  • ***
  • Posts: 9961
  • Country: 00
Re: DS1054Z distortion issue?
« Reply #37 on: April 28, 2016, 08:32:09 am »
It is unreasonable to expect that manufacturers can specify all ways in which an instrument can mislead the unwary.

Would it help sales if a manufacturer put those screenshots on their web site?    :-/O


 

Offline Keysight DanielBogdanoff

  • Frequent Contributor
  • **
  • Posts: 685
  • Country: us
  • ALL THE SCOPES!
    • Keysight Scopes YouTube channel
Re: DS1054Z distortion issue?
« Reply #38 on: April 28, 2016, 04:39:38 pm »
Anyway, it would be a good idea to have a sticky thread with a pointer to some DSO tutorials. At least the three sisters have produced excellent tutorials available for free ;)

Shameless plug, I'm actually working on a video series on our YouTube channel that covers scope basics. I have a month or two of videos planned out, but am pretty flexible if there are specific topics that you folks think are extra important.  Just comment on one of those videos with your suggestions; that's where I get my video request list from.

Regarding dynamic range.  Long story short is all scopes have amplifiers, and if the amplifiers saturate there's going to be weird results.  It scares me that some scope vendors don't specify their dynamic range, because then you never know 100% that an off-screen signal isn't violating the DR.
 
The following users thanked this post: Marcos

Online tggzzz

  • Super Contributor
  • ***
  • Posts: 9855
  • Country: gb
    • Having fun doing more, with less
Re: DS1054Z distortion issue?
« Reply #39 on: April 28, 2016, 05:11:43 pm »
Regarding dynamic range.  Long story short is all scopes have amplifiers, and if the amplifiers saturate there's going to be weird results.  It scares me that some scope vendors don't specify their dynamic range, because then you never know 100% that an off-screen signal isn't violating the DR.

It may not be that simple with multiple amplifiers and multiple attenuators.

For comparison, spectrum analysers often quote performance based on power level "at the mixer" - even though that isn't directly related to the input power, plus the position on the display will depend on many of the SA's settings. They presume the user has sufficient knowledge of their system and the SA's internals and settings that the user can mentally calculate that.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Online borjam

  • Supporter
  • ****
  • Posts: 738
  • Country: es
  • EA2EKH
Re: DS1054Z distortion issue?
« Reply #40 on: April 28, 2016, 05:33:54 pm »
Shameless plug, I'm actually working on a video series on our YouTube channel that covers scope basics. I have a month or two of videos planned out, but am pretty flexible if there are specific topics that you folks think are extra important.  Just comment on one of those videos with your suggestions; that's where I get my video request list from.

Regarding dynamic range.  Long story short is all scopes have amplifiers, and if the amplifiers saturate there's going to be weird results.  It scares me that some scope vendors don't specify their dynamic range, because then you never know 100% that an off-screen signal isn't violating the DR.
In those cases, some overload indication would certainly help. Actually, there could be two overload conditions worthy of being reported. Out of the A/D dynamic range and amplifier overload ;)

I'll have to check out those videos, thank you!

And of course I'll pester you with suggestions if I have any!
 

Offline pxl

  • Regular Contributor
  • *
  • Posts: 126
  • Country: hu
Re: DS1054Z distortion issue?
« Reply #41 on: April 28, 2016, 05:43:42 pm »
I really don't get it ^^^  :-//  :scared:  :bullshit:
Just why would anybody want/need to use a DSO in that way?

E.g: checking a 10 V zero crossing glitch on a 300 Vpp signal (with a 1:10 probe).
Really  :o Nah, there's gotta be a better method than having the scope free-run and the vertical over-driven like that.

More attenuation, set trigger appropriately, capture the waveform of interest THEN magnify with increased sensitivity.

Make the power of a DSO work for you.  ;)

This. ^

At what point do you start damaging the vertical amplifiers and/or attenuators?

I can just imagine the conversation:
Customer: One channel doesn't work right any more.
CS rep: When did you first notice this?
Customer: When I applied a 30V p-p signal and I had the V/div set at 10 mV/div.
CS rep:   :palm:

It is not specified that the maximum allowable voltage should be used only the largest vertical settings, so it should not damage the scope. :-+
« Last Edit: April 29, 2016, 09:37:14 am by pxl »
 

Online Performa01

  • Frequent Contributor
  • **
  • Posts: 815
  • Country: at
Re: DS1054Z distortion issue?
« Reply #42 on: April 29, 2016, 08:36:06 am »
Regarding dynamic range.  Long story short is all scopes have amplifiers, and if the amplifiers saturate there's going to be weird results.

That's correct. No amplifier will work as specified if the conditions that the specifications are based on aren't met. In this case, the signal exceeds the specified CMR, which causes internal bias points to shift, some transistors to turn off and others to saturate. The output signal might change polarity and in any case it will take a little while until the amplifier recovers after the overload has been removed.


Quote
It scares me that some scope vendors don't specify their dynamic range, because then you never know 100% that an off-screen signal isn't violating the DR.

Well, some scope vendors don't need to, as with proper design all these nasty things will not happen in the first place. It's just a matter of having a proper limiter at the input of the amplifier, preventing it to get overloaded. Then we can indeed zoom into a signal vertically, even 100 times, without any adverse effects.
« Last Edit: April 29, 2016, 08:39:07 am by Performa01 »
 

Offline alsetalokin4017

  • Super Contributor
  • ***
  • Posts: 1878
  • Country: us
Re: DS1054Z distortion issue?
« Reply #43 on: April 29, 2016, 08:53:45 am »
Quote
Well, some scope vendors don't need to, as with proper design all these nasty things will not happen in the first place. It's just a matter of having a proper limiter at the input of the amplifier, preventing it to get overloaded. Then we can indeed zoom into a signal vertically, even 100 times, without any adverse effects.

But... but.... this is a Rigol DS1054z we are talking about here!  You know... the scope that shows RMS voltage measurements on channels that are grounded! That has Measurements that simply stop working at random times when Math is in use, that miscounts "Pluses", that has the horizontal Math error at 500 ns/div..... etc.    :rant:

Should we have confidence that this particular scope model has proper limiters at the front end so that we don't get _really_ adverse effects, like blown inputs, if we zoom in vertically 100 times? Who is willing to put their DS1054z to the test, providing a 300V p-p signal and then zooming in 100x? Sorry... not I.    :scared:
The easiest person to fool is yourself. -- Richard Feynman
 

Online Performa01

  • Frequent Contributor
  • **
  • Posts: 815
  • Country: at
Re: DS1054Z distortion issue?
« Reply #44 on: April 29, 2016, 09:02:51 am »
Should we have confidence that this particular scope model has proper limiters at the front end so that we don't get _really_ adverse effects, like blown inputs, if we zoom in vertically 100 times? Who is willing to put their DS1054z to the test, providing a 300V p-p signal and then zooming in 100x? Sorry... not I.    :scared:

Well, there is no input limiter in the DS1000Z as the initial posting clearly demonstrates.
That doesn't mean that it won't withstand the rated max. input voltage. Quite obviously the designers rely on the internal input protection of the first OpAmp, which might well be sufficient to survive, but isn't good design practice for sure.
 

Online tggzzz

  • Super Contributor
  • ***
  • Posts: 9855
  • Country: gb
    • Having fun doing more, with less
Re: DS1054Z distortion issue?
« Reply #45 on: April 29, 2016, 09:07:42 am »
Well, some scope vendors don't need to, as with proper design all these nasty things will not happen in the first place. It's just a matter of having a proper limiter at the input of the amplifier, preventing it to get overloaded.

I'm glad you know how to do that, since you can patent and sell your techniques, and they will make you rich.

Unfortunately "adding limiters" isn't that simple, of course.

Limiters are non-linear circuit elements that will affect (i.e. distort) the signals even when they aren't limiting. In a scope distortion is to be avoided, which implies limiters might need to be avoided. Many scope and spectrum analysers are deliberately left "unprotected" for that reason - even though their lack means the instrument would be destroyed by too large signals.

Plus, of course, there are many amplifiers in a scope, any of which could be overloaded. "Protection" would require many non-linear elements in the signal path, which is even more problematic!
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Online Performa01

  • Frequent Contributor
  • **
  • Posts: 815
  • Country: at
Re: DS1054Z distortion issue?
« Reply #46 on: April 29, 2016, 09:31:51 am »
I'm glad you know how to do that, since you can patent and sell your techniques, and they will make you rich.

Unfortunately "adding limiters" isn't that simple, of course.

Well, it's not rocket science. Of course it can be done. I have done it and scope vendors seem to have successfully done it as well.
So no chance getting a patent on that.

Quote
Limiters are non-linear circuit elements that will affect (i.e. distort) the signals even when they aren't limiting. In a scope distortion is to be avoided, which implies limiters might need to be avoided. Many scope and spectrum analysers are deliberately left "unprotected" for that reason - even though their lack means the instrument would be destroyed by too large signals.

Yes, for an instrument promising a 3rd order dynamic range of 70dB and operating up to several GHz, a limiter would be a challenge indeed. Not saying it cannot be done, but that's something I haven't tried before and would actually expect some degradation in performance.

But we are talking about general purpose 8-bit scopes in the couple 100MHz range here. With an INL of at least +/- 0.5LSB there's not much to worry about the linearity of the frontend.

Quote
Plus, of course, there are many amplifiers in a scope, any of which could be overloaded. "Protection" would require many non-linear elements in the signal path, which is even more problematic!

No, there aren't. Neither many amplifiers, nor particular non-linear elements.

Apart from that, I'm pretty sure even the Rigol DS1000Z will have some clamping diodes at the input - just clamping to the supply rails instead to a specific voltage level that prevents the amplifier from leaving its specified common mode range.

 

Online Fungus

  • Super Contributor
  • ***
  • Posts: 9961
  • Country: 00
Re: DS1054Z distortion issue?
« Reply #47 on: April 29, 2016, 09:33:24 am »
Should we have confidence that this particular scope model has proper limiters at the front end so that we don't get _really_ adverse effects, like blown inputs, if we zoom in vertically 100 times? Who is willing to put their DS1054z to the test, providing a 300V p-p signal and then zooming in 100x? Sorry... not I.    :scared:

Why don't you tell us, Mr. self-appointed Rigol expert? The schematic is out there.
 

Online tggzzz

  • Super Contributor
  • ***
  • Posts: 9855
  • Country: gb
    • Having fun doing more, with less
Re: DS1054Z distortion issue?
« Reply #48 on: April 29, 2016, 10:35:30 am »
Plus, of course, there are many amplifiers in a scope, any of which could be overloaded. "Protection" would require many non-linear elements in the signal path, which is even more problematic!
No, there aren't. Neither many amplifiers, nor particular non-linear elements.

Look again. Start with the discrete components in the input stage signal path. Then move onto looking inside the ICs such as the LMH6552 (or similar), and others.

Hint: all oscilloscopes have multiple amplifiers, some in series and some in parallel.

Quote
Apart from that, I'm pretty sure even the Rigol DS1000Z will have some clamping diodes at the input - just clamping to the supply rails instead to a specific voltage level that prevents the amplifier from leaving its specified common mode range.

They do have diodes, just like other low-end scopes. But they are nothing whatsoever to do with common mode ranges.

Have a look at or similar; if you spot what you are thinking of, please point to it.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline alsetalokin4017

  • Super Contributor
  • ***
  • Posts: 1878
  • Country: us
Re: DS1054Z distortion issue?
« Reply #49 on: April 29, 2016, 01:42:20 pm »
Should we have confidence that this particular scope model has proper limiters at the front end so that we don't get _really_ adverse effects, like blown inputs, if we zoom in vertically 100 times? Who is willing to put their DS1054z to the test, providing a 300V p-p signal and then zooming in 100x? Sorry... not I.    :scared:

Why don't you tell us, Mr. self-appointed Rigol expert? The schematic is out there.

I've never claimed to be a Rigol expert.  I'm a USER of this model scope-- at least I try to use its features and functions, in spite of its many problems. My post points out that we may not be justified in having supreme confidence in the hardware design, bearing in mind the many software problems that plague this model scope.

Why don't YOU test _your_ DS1054z for us, using the maximum rated input voltage and then zooming in to more and more vertical sensitivity? I'm sure we all would be interested in seeing your report. Do you have the necessary confidence in the Rigol hardware design?
 
 :popcorn:
« Last Edit: April 29, 2016, 01:45:35 pm by alsetalokin4017 »
The easiest person to fool is yourself. -- Richard Feynman
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf