Choosing between entry-level 12-bit DSOs

[Fungus]

I'm afraid I don't follow. What exactly would go wrong if you sample a 250 MHz signal at 1 GSa/s?

Does it have 1 GSa/s with 4 channels on?

[BillyO]

What if somebody feeds in a 250MHz signal into a Siglent by mistake?

Then they've made a mistake and will get mistaken results.  This has little to do with the fact that the Siglent is the better scope, regardless what errors are made.

Seems like a pointless discussion anyway.  Like splitting hairs.  Some people like Rigol, some like Siglent and when they are as close as these two, that's probably going to be the deciding factor.

[ebastler]

I'm afraid I don't follow. What exactly would go wrong if you sample a 250 MHz signal at 1 GSa/s?

Does it have 1 GSa/s with 4 channels on?

Could you please read my post #396, man? And ideally try to understand it? It's not that long or difficult.

[Fungus]

Could you please read my post #396, man? And ideally try to understand it? It's not that long or difficult.

It's a simple yes or no question.

[Fungus]

Seems like a pointless discussion anyway.  Like splitting hairs.  Some people like Rigol, some like Siglent and when they are as close as these two, that's probably going to be the deciding factor.

To me it seems like BMW vs Mercedes. They're different, for different people.

[ebastler]

Could you please read my post #396, man? And ideally try to understand it? It's not that long or difficult.

It's a simple yes or no question.

With three or four channels active, the SDS800X HD series samples at 500 MSa/s. But it switches in an additional 200 MHz low-pass filter in its front end in that mode, to ensure that frequency components aboove the Nyquist limit are properly suppressed.

This is the third time I have told you. I have also given you a link to actual measurements. But I have very little hope that you can process that information.

I hate using this icon on others, but it is warranted here: 

[Fungus]

With three or four channels active, the SDS800X HD series samples at 500 MSa/s. But it switches in an additional 200 MHz low-pass filter in its front end in that mode, to ensure that frequency components aboove the Nyquist limit are properly suppressed.

Ok, thanks for posting that clearly.

I didn't know it had that sample rate with 4 channels on.

But still, near-zero practical difference to most people in this category, and a "Pro" would probably want something with a bigger screen.

[Mechatrommer]

after the age of CRT era... get a real oscilloscope...
https://www.ebay.com.my/itm/186133520067
so you wont be bothered by never ending aliasing argumentation nonsense

[2N3055]

What if somebody feeds in a 250MHz signal into a Siglent by mistake?

Then they've made a mistake and will get mistaken results.  This has little to do with the fact that the Siglent is the better scope, regardless what errors are made.

Seems like a pointless discussion anyway.  Like splitting hairs.  Some people like Rigol, some like Siglent and when they are as close as these two, that's probably going to be the deciding factor.

If you were discussing look and feel I would  agree. If someone says "I understand SDS800xHD has better math but I don't care for that I like that DHO800 has HDMI out" who am I to argue. People know their priorities.

And I did say, on the record, that I do think that DHO800 is potentially nice little 100MHz entry level scope. I think it is buggy as hell and limited, but some people choose to live with bugs and don't need anything more than basic. And hope is (I'm sceptical at this point, but not important) Rigol will eventually iron it out to point of being rid of obvious bugs.

But facts are facts and DHO900 is hardware that is a shame of Rigol and should not have left prototype phase. It is a 250MHz scope (claimed) that in worst case samples at 156MSps/s which is FINRSI type of specmanship.
And since many people hack their DHO800 to 900 that defect is applicable to 800 too.

And then they say it is same as SDS800xHD.
It is not.
SDS800xHD is properly, professionally designed scope.
It is serious instrument.

And then there are people here that try to rewrite science to make complete lies and nonsense true because Rigol must be best... Even if it is a lie.

[KungFuJosh]

But still, near-zero practical difference to most people in this category, and a "Pro" would probably want something with a bigger screen.

That's a weird response to one of the devices simply having superior hardware. 🤷

[2N3055]

But still, near-zero practical difference to most people in this category, and a "Pro" would probably want something with a bigger screen.

That's a weird response to one of the devices simply having superior hardware. 🤷

Weird responses are his speciality!!

[ebastler]

What if somebody feeds in a 250MHz signal into a Siglent by mistake?

Then they've made a mistake and will get mistaken results.  This has little to do with the fact that the Siglent is the better scope, regardless what errors are made.

Seems like a pointless discussion anyway.  Like splitting hairs.  Some people like Rigol, some like Siglent and when they are as close as these two, that's probably going to be the deciding factor.

I hope it has become clear in the exchange with Fungus, but just to be sure:

The thing is that the user will not get mistaken results from the Siglent. The SDS800X HD either has ample sampling rate (1 or 2 GHz in dual or single-channel mode) and reconstructs the 250 MHz signal properly. Or, when it falls back to 500 MSa/s in three or four-channel mode, it activates a dedicated 200 MHz low-pass filter in its front end, to ensure that no frequency components above the Nyquist limit come through and cause aliasing.

[ebastler]

But still, near-zero practical difference to most people in this category, and a "Pro" would probably want something with a bigger screen.

That's a weird response to one of the devices simply having superior hardware. 🤷

Once there is no further denying that not only the competitor's hardware is better, but they also handle the eventual limitations properly, the second line of defense is to argue that the difference is not important. 

Which, by the way, is a pattern I have also seen in discussions about Siglent design limitations, e.g. the paired vertical pixels in the SDS800X HD. Just sayin'...   

[BillyO]

SDS800xHD is properly, professionally designed scope.
It is serious instrument.

And that's why I bought one.

And then there are people here that try to rewrite science to make complete lies and nonsense true because Rigol must be best... Even if it is a lie.

I call this "flat earth type mentality".  You see it every where you go.  It's basically confirmation bias at a world-view level.

[Fungus]

The thing is that the user will not get mistaken results from the Siglent. The SDS800X HD either has ample sampling rate (1 or 2 GHz in dual or single-channel mode) and reconstructs the 250 MHz signal properly. Or, when it falls back to 500 MSa/s in three or four-channel mode, it activates a dedicated 200 MHz low-pass filter in its front end, to ensure that no frequency components above the Nyquist limit come through and cause aliasing.

ie. A 250Mhz signal won't be the correct amplitude on your Siglent.

I can leave my Rigol at 125MHz (measured) and it'll be good in all circumstances.

125Mhz is just as arbitrary a number as 200Mhz is.

[2N3055]

But still, near-zero practical difference to most people in this category, and a "Pro" would probably want something with a bigger screen.

That's a weird response to one of the devices simply having superior hardware. 🤷

Once there is no further denying that not only the competitor's hardware is better, but they also handle the eventual limitations properly, the second line of defense is to argue that the difference is not important. 

Which, by the way, is a pattern I have also seen in discussions about Siglent design limitations, e.g. the paired vertical pixels in the SDS800X HD. Just sayin'...

Since it was me I will reply:

We are talking about visual difference that is something that some people don't see.
Compared to violating Nyquist.

One is compromise because of limited resources, other one is failed basic law of sampling.
Those two are nothing like.

And that is also something. Comparing blaring mistakes on one side with minor imperfections on the other side and saying "ha you see they BOTH have mistakes...."


Fact that you don't accept that myself with my glasses and myopia literally didn't see the difference before it was pointed out to me, at which moment I had to come close to screen to actually verify you are correct, is your problem that in that argument you had to win at any cost.  Therefore you accused me of lying, instead of thinking that maybe you are shaming me for not having perfect vision...

So yeah not the same, not even close...

[2N3055]

The thing is that the user will not get mistaken results from the Siglent. The SDS800X HD either has ample sampling rate (1 or 2 GHz in dual or single-channel mode) and reconstructs the 250 MHz signal properly. Or, when it falls back to 500 MSa/s in three or four-channel mode, it activates a dedicated 200 MHz low-pass filter in its front end, to ensure that no frequency components above the Nyquist limit come through and cause aliasing.

ie. A 250Mhz signal won't be the correct amplitude on your Siglent.

I can leave my Rigol at 125MHz (measured) and it'll be good in all circumstances.

125Mhz is just as arbitrary a number as 200Mhz is.

If you use your DHO800 at factory 125Mhz it is all good and well and no problem.
DHO900 is a mess OTOH.

[BillyO]

The thing is that the user will not get mistaken results from the Siglent.

I agree with you.  My point was more, if he measured the wrong signal (the mistake) then he will get the wrong results.  I was not actually trying to comment on the scope's capabilities.  I admit I was not clear in tis respect.

[Fungus]

But facts are facts and DHO900 is hardware that is a shame of Rigol and should not have left prototype phase. It is a 250MHz scope (claimed) that in worst case samples at 156MSps/s which is FINRSI type of specmanship.

No disagreement there, but let's not forget the Siglent logic adapter is severely compromised, too.

[Fungus]

If you use your DHO800 at factory 125Mhz it is all good and well and no problem.

It's enough for me right now.

If I need more bandwidth I can just double-click a .bat file on my PC and I can have 250MHz in 10 seconds.

(nb. You don't need to reboot, just kill/restart the 'scope app).

I'm aware of the limits when I do that. It's very easy to turn channels on/off to check for aliasing.

[2N3055]

But facts are facts and DHO900 is hardware that is a shame of Rigol and should not have left prototype phase. It is a 250MHz scope (claimed) that in worst case samples at 156MSps/s which is FINRSI type of specmanship.

No disagreement there, but let's not forget the Siglent logic adapter is severely compromised, too.

No it is not severely compromised, it has certain limitations. That are clearly documented, and you actually heard it from "Siglent crowd". There are limitations in real time zoom, and triggering from mixed channels.
But OTOH, it samples at blazing 1GS/s and does not impact scope own sampling or memory.

So limited it is, compromised it is not.

[ebastler]

So yeah not the same, not even close...

I agree, and did not mean to imply that the two limitations are comparable. Just the pattern of argumentation.

Having used the SDS814X HD for nearly two months now, I can confirm that the resolution limitation is not a problem -- although I do notice it at times, especially with flattish signal slopes. If I had shelled out extra money for the larger screen in a 1000X HD, I would probably be annoyed about it.

[Mechatrommer]

Compared to violating Nyquist.

please note what you keep talking is a combination of sample rate and Sinc reconstruction. turn off Sinc and your point will become moot, granted signal can be a little weird when spectral content contains element more than half the sampling rate, using "Line" or vector plot. but not as severe when your turn on Sinc. we are waiting Rigol to enable back turning off Sinc feature in newer FW that they should not fucked up with in the first place. otoh if you ask me, if its feasible i'll modify one channel to become 500MHz on DHO900 (hacked DHO800) anytime if i need it to be... or 800MHz BW on SDS824X (if possible hacked from SDS804X) we know what we are dealing with.

[ebastler]

please note what you keep talking is a combination of sample rate and Sinc reconstruction. turn off Sinc and your point will become moot, granted signal can be a little weird when spectral content contains element more than half the sampling rate, using "Line" or vector plot. but not as severe when your turn on Sinc.

Umm... How would you describe, say, a 170 MHz sine signal sampled at 312 MSa/s, when shown in dot mode or with linear interpolation? It would look severely misleading in my book. Sinc interpolation is not the issue here.

[2N3055]

So yeah not the same, not even close...

I agree, and did not mean to imply that the two limitations are comparable. Just the pattern of argumentation.

Having used the SDS814X HD for nearly two months now, I can confirm that the resolution limitation is not a problem -- although I do notice it at times, especially with flattish signal slopes. If I had shelled out extra money for the larger screen in a 1000X HD, I would probably be annoyed about it.

And I fully appreciate that you do notice it and that it would bother you.

I, personally, couldn't care less, because when I put my KS MSO-X3104T next to it, SDS800xHD feels like 4K compared to VHS....   

And because there is always one pixel worth of noise when running, you don't see the difference to SDS2000xHD, 3000xHD. Only when you stop it, then you can see it. And yes it is there. But I didn't notice it before you mentioned it.  I blame you ...