Choosing between entry-level 12-bit DSOs

[gf]

Here you go:
SDS824X HD_Sine_450MHz_1GSa_Single

here you demo that at some setup Sr / 2.22, sds800x is unable to reconstruct signal properly? from the look of it, yes it is.

The image seems to be named incorrectly. This was 490 MHz, or sample_rate / 2.04.

[gf]

Hence I would stick with my conclusion that we still get a stable interpolation at sampling freq / 2.22.

Well, quantify "stable". In the SDS824X HD_Sine_450MHz_1GSa_FFT screenshot, we see a signal to distortion ratio of about 28 dB (about 4% distortion) for f=0.45*sample_rate. Whether you consider that to be good or bad is relative, but it is already perceptible.

[Mechatrommer]

The image seems to be named incorrectly. This was 490 MHz, or sample_rate / 2.04.

ok i stand corrected. improper reconstruction at very very near to Sr / 2 is of course acceptable. proper reconstruction at Sr / 2.2 is already good.

Hence I would stick with my conclusion that we still get a stable interpolation at sampling freq / 2.22.

Well, quantify "stable". In the SDS824X HD_Sine_450MHz_1GSa_FFT screenshot, we see a signal to distortion ratio of about 28 dB (about 4% distortion) for f=0.45*sample_rate. Whether you consider that to be good or bad is relative, but it is already perceptible.

lets make it "relative measurement" how good sds800x relative to dho800... the answer is quite clear for me.

[2N3055]

Discussion is going in wrong direction. Beginner that wants entry level scope has no knowledge to understand all DSP stuff being discussed. They need device to simply work. User will bring in enough of it's own confusion into the process.

Rigol (unlocked to to 250 MHz) and applied 200 MHz signal to all enabled channels
1Ch    (1,25 GS/s) - OK
2Ch    (625 MS/sec) - OK
3Ch    (312,5 MS/s) - NOT OK
4Ch    (312,5 MS/s) - NOT OK

Siglent (licensed to SDS824xHD) and applied 200 MHz signal to all enabled channels
1Ch    (2 GS/s) - OK
2Ch    (1 GS/sec) - OK
3Ch    (500 MS/s) - OK
4Ch    (500 MS/s) - OK

One of these scopes is 4 Ch 200 MHz scope and one is 2Ch 250MHz scope (or 4Ch 100MHz scope).
Guess which one is which.

[Fungus]

Discussion is going in wrong direction. Beginner that wants entry level scope has no knowledge to understand all DSP stuff being discussed. They need device to simply work. User will bring in enough of it's own confusion into the process.

Rigol UI is better for a beginner so that's probably bad advice. Better to have the stuff they do 99% of the time easy to do than to make life life difficult for some theoretical thing that they might never do.

A "beginner that wants entry level 'scope" probably has no 200Mhz signals lying around anyway.

(I'm not even sure I do...)

Rigol (unlocked to to 250 MHz) and applied 200 MHz signal to all enabled channels

Where's it written that people must do that?

(Be honest, do YOU do that...?)

[awakephd]

I agree that the machine tool analogy proved to be less than helpful. It was intended to illustrate the different needs and perspectives of hobby users vs. professionals, but seemed to slide off into a discussion about size. Somehow, as a 63-year-old male, it always seems to come back to a debate about size ...

I keep wanting to like the Siglent; I really do. It seems so obviously to be the sensible option. But honestly, every time you all post screen shots of the Siglent next to screen shots of the Rigol, I feel like the Siglent is harder to read, as though I will constantly have to be peering closely to distinguish between one measurement and the next. Meanwhile, the Rigol screen seems vibrant, much easier to pick out salient numbers. Is that just my inexperience showing?

Maybe a different analogy will work. The Siglent seems like a Toyota - the reliable, practical, capable choice. But the Rigol seems more like a Miata - looks good, so fun to drive, even if it is a bit cramped and really doesn't have that much power under the hood. Which one is the best choice? If I relied on the vehicle as my primary transportation, I would unquestionably take the Toyota. Since I don't actually need this vehicle ... I don't make a living at this, and will only take it out for a drive on occasion ... it is hard to walk away from the Miata. One seems like it will be work to drive - not hard work, but straightforward, no nonsense, no desire to take it out for a spin just because. The other seems like something I would enjoy taking out for a joy ride.

Feel free to tell me I'm crazy. I certainly have read the comments in other threads that disparage the UI of the Rigol as amateurish, etc. Well ... I'm an amateur ... they sure have caught my eye. But I really don't want to buy, say, a Dodge Charger on its sex appeal, only to find that I can't take it out for a joy ride because it is too unreliable.

Maybe I should give up on trying to generate analogies ... I think I'm going from bad to worse!

[Performa01]

here you demo that at some setup Sr / 2.22, sds800x is unable to reconstruct signal properly? from the look of it, yes it is.

Not correct. What I've shown is the behavior at SR / 2.04, not 2.22. The input signal was a 490 MHz sine.

[tggzzz]

A "beginner that wants entry level 'scope" probably has no 200Mhz signals lying around anyway.

Really? No risetimes[1] less than 2ns? Must be restricting themselves to early 1980s logic families. By the late 80s several TTL families were below that, and a few were below 1ns. Since then things have got faster

Example refs, use gurgle for others: https://www.oreilly.com/library/view/complete-pcb-design/9780128176856/xhtml/app003.xhtml https://ve2zaz.net/referenc/LogicT.htm

[1] No, the period doesn't count; it is completely irrelevant in this context.

[tggzzz]

I agree that the machine tool analogy proved to be less than helpful.
...
Maybe I should give up on trying to generate analogies ... I think I'm going from bad to worse!

That frequently happens with analogies Analogies are often dangerous

[nctnico]

I agree that the machine tool analogy proved to be less than helpful. It was intended to illustrate the different needs and perspectives of hobby users vs. professionals, but seemed to slide off into a discussion about size. Somehow, as a 63-year-old male, it always seems to come back to a debate about size ...

I keep wanting to like the Siglent; I really do. It seems so obviously to be the sensible option. But honestly, every time you all post screen shots of the Siglent next to screen shots of the Rigol, I feel like the Siglent is harder to read, as though I will constantly have to be peering closely to distinguish between one measurement and the next. Meanwhile, the Rigol screen seems vibrant, much easier to pick out salient numbers. Is that just my inexperience showing?

No it is not you. The Siglent UI is more cluttered compared to Rigol's UI. Rigol has done a better job in that respect (if the rest of the scope would work). Siglent's UI is copied from Lecroy's UI and not necessarily laid out very well. The aim is to cram as much information as possible in one screen without much thought for following good UI design guidelines. IMHO both Rigol and Siglent products are always lacking in one way or another. If you could create a mash-up between the both, you'd end up with a piece of equipment which ticks more boxes.

[ebastler]

A "beginner that wants entry level 'scope" probably has no 200Mhz signals lying around anyway.
(I'm not even sure I do...)

Rigol (unlocked to to 250 MHz) and applied 200 MHz signal to all enabled channels

Where's it written that people must do that?
(Be honest, do YOU do that...?)

Digital signals from today's logic families easily have edges with much higher frequency content than 200 MHz -- even signals relevant for amateurs.

It's enough to need to look at one fast signal, in the context of (e.g. gated and triggered by) two other signals. E.g. one critical signal where you need to check signal quality -- say a clock -- which may get distorted due to interference from some other lines.

Edit: Or turn the example scenario around, that's probably even more relevant in practice: You have some digital signals which show an unexpected behaviour, and you want to check whether it is caused by a malformed clock, glitches or such. So you need to gate and trigger based on those erroneous signals (but may not need the full bandwidth for these), and at the same time look at the suspected clock with the highest bandwidth you can get. 

[shapirus]

Rigol UI is better for a beginner

It's very subjective. It needs proof/demonstration in the form of describing specific use cases where a beginner would benefit from specific features in the Rigol's UI that are missing or implemented differently in the Siglent's one.

I would argue that the Rigol's UI is bad (note that I'm not making comparisons here) regardless of the user's level.
For one thing, as was mentioned before, it wastes a lot of screen area for displaying elements bearing no practical usefulness. That's only to begin with.
On top of that it has annoying glitches and/or bugs with zooming.
It also doesn't display the currently selected probe attenuation ratio, which is bad for an advanced user, but even more so for a beginner.
The list can go on. It's just what I can immediately point out.

I own a DHO800 and I'm not gonna blindly defend it just because of that. It has a few things implemented better than in the Siglent: the effective display resolution of the waveform trace comes to mind, for example, or the higher refresh rate in the webcontrol app, and those are no tiny things to mention. I would be really pissed off if I bought a 12-bit scope only to discover that the traces it displays were upscaled from a low-res source.
But otherwise, as, again, was already said and discussed in depth, its UI sucks, plain and simple. It was not developed by someone who understood that the target device was one of the test and measurement equipment category.

A "beginner that wants entry level 'scope" probably has no 200Mhz signals lying around anyway.

The frequency is in the transition edges, not (just) in the fundamental. And fast chips are ubiquitous.

Rigol fails miserably at fast edges with more than 1 channel on.


1 channel: good




2 channels: poor




3 channels: terrible

[shapirus]

Regarding the "beginner/non-beginner" argument: any beginner stops being such very quickly, but the tool tailored for beginners (assuming it is) will remain such forever.

[Antonio90]

I agree that the machine tool analogy proved to be less than helpful. It was intended to illustrate the different needs and perspectives of hobby users vs. professionals, but seemed to slide off into a discussion about size. Somehow, as a 63-year-old male, it always seems to come back to a debate about size ...

I keep wanting to like the Siglent; I really do. It seems so obviously to be the sensible option. But honestly, every time you all post screen shots of the Siglent next to screen shots of the Rigol, I feel like the Siglent is harder to read, as though I will constantly have to be peering closely to distinguish between one measurement and the next. Meanwhile, the Rigol screen seems vibrant, much easier to pick out salient numbers. Is that just my inexperience showing?

No it is not you. The Siglent UI is more cluttered compared to Rigol's UI. Rigol has done a better job in that respect. Siglent's UI is copied from Lecroy's UI and not necessarily laid out very well. The aim is to cram as much information as possible in one screen without much thought for following good UI design guidelines.

It is cluttered. Still, that is not a problem for basic probing around, and you can get used to the UI and/or use the web server. I think that being a beginner without previous expectations about how an oscilloscope should work is actually an advantage in this instance, as you are going to have to learn the instrument anyway.

In any case, I don't find the UI bad, quite the opposite, but it certainly looks as if it was designed for a bigger screen. I just rearranged my workbench a bit and put the oscilloscope a bit closer, and the soldering tools further away.

[Fungus]

honestly, every time you all post screen shots of the Siglent next to screen shots of the Rigol, I feel like the Siglent is harder to read, as though I will constantly have to be peering closely to distinguish between one measurement and the next. Meanwhile, the Rigol screen seems vibrant, much easier to pick out salient numbers. Is that just my inexperience showing?

Nope, I agree 100% (and have said so many times).

The text rendering on the Rigol is amazing. Very, very easy on the eyes. Even better in person than in screenshots posted here.

I haven't seen a Siglent in person but the screenshots don't give me any hope.

[Fungus]

Really? No risetimes[1] less than 2ns?

Certainly not on an Arduino.

[Fungus]

Digital signals from today's logic families easily have edges with much higher frequency content than 200 MHz -- even signals relevant for amateurs.

So you need more than the Siglent for "digital".

eg. Something like a Rigol MSO5000 with 350Mhz bandwidth and 8GS/sec sample rates.

I've been saying all along that the "200Mhz" number is very arbitrary, made up by Siglent users because it fits their agenda.

[Fungus]

Regarding the "beginner/non-beginner" argument: any beginner stops being such very quickly, but the tool tailored for beginners (assuming it is) will remain such forever.

I wouldn't call myself a beginner but I'm happy with my Rigol.

I'm simply never going to connect four 200MHz signals to it.

(because I have no need to)

[Fungus]

Persistance isn't helping your argument.

If I need to measure rise times accurately I can use 1 channel. Not a problem.

And again: Is the Siglent's bandwidth enough? 200Mhz doesn't seem enough for the job you're proposing. Maybe get a Rigol MSO5000 instead.

[tggzzz]

Regarding the "beginner/non-beginner" argument: any beginner stops being such very quickly, but the tool tailored for beginners (assuming it is) will remain such forever.

I wouldn't call myself a beginner but I'm happy with my Rigol.

I'm simply never going to connect four 200MHz signals to it.

(because I have no need to)

You don't need to.

Connecting four 1Hz signals with transition times <2ns is sufficient. Big hint: the circuit neither "knows" nor "cares" when the next transition might occur.

The other issue is ensuring t_hold requirements are met. Those are fixed for a given logic family, are <<t_clock, and reducing the clock frequency doesn't help (unlike t_setup).

[Fungus]

Regarding the "beginner/non-beginner" argument: any beginner stops being such very quickly, but the tool tailored for beginners (assuming it is) will remain such forever.

I wouldn't call myself a beginner but I'm happy with my Rigol.

I'm simply never going to connect four 200MHz signals to it.

(because I have no need to)

You don't need to.

Connecting four 1Hz signals with transition times <2ns is sufficient.

OK, discussion has been changed from sine waves and Nyquist limits to pulses just for me... got it.

Better questions:

What job can't I do with my Rigol?

ie. What's an example of a showstopping problem where I'd have no choice but to go out and buy a Siglent instead?

[2N3055]

Really? No risetimes[1] less than 2ns?

Certainly not on an Arduino.

Atmega328 easily creates sub 1ns edges...
Not to mention ARM based Arduinos...
Raspberry PI has sub 500ps edges...

Fact that you think world ends with your Rigol makes no difference to actual facts...

[Fungus]

Atmega328 easily creates sub 1ns edges...

Not on a wire connected to the output of an Arduino Uno it doesn't.

[2N3055]

Atmega328 easily creates sub 1ns edges...

Not on a wire connected to the output of an Arduino Uno it doesn't.

How would you know if you didn't try it with 1GHz scope and active probe?

[shapirus]

Persistance isn't helping your argument.

Persistence was set to the minimum possible value in that screenshot. There's no way to fully disable persistence that I know of, but we can simulate it by reducing the waveform acquisition rate. Here you go:



Is it better? Maybe, it depends. Both modes suck, each in its own way.

If I need to measure rise times accurately I can use 1 channel. Not a problem.

It's not about (just) measuring rise times. Both the scopes in question are useless for measuring sub-nanosecond rise times anyway.

It's about observing short pulses, or intermittent glitches, or debugging signal integrity issues and visualizing transitions in digital circuits in general, where having to correlate one signal (e.g. clock) to another one or several is a legit and common use case: it requires both looking at transitions and having multiple inputs enabled at the same time.

Is the Rigol's inability to properly display such waveforms fatal? No, by no means it's not: after all, it doesn't fail to display them completely, so you will see it if there is something. Will it prevent the job from being done? No it will not, at least as long as the user is aware of these edge case (pun intended!) shortcomings.
But does it suck? That's subjective, but I say oh yes it sure does, especially because there is a scope at (typically) the same price point which will display such pulses correctly with little or no wobbling like that. How do I know? At this point I'm not gonna bother searching for screenshots proving it, I've already seen enough. I would be very happy to be proven wrong, though.

And again: Is the Siglent's bandwidth enough? 200Mhz doesn't seem enough for the job you're proposing. Maybe get a Rigol MSO5000 instead.

It's not (only) a bandwidth issue. It's the failure to interpolate the sample data points correctly.