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Siglent SDS1104X-E anomaly on what should be a simple task.

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py-bb:

--- Quote from: 2N3055 on December 28, 2022, 02:00:33 pm ---
--- Quote from: py-bb on December 28, 2022, 11:58:25 am ---Okay I did the experiment.

First up the full wave we're viewing. There is a 50 ohm terminator in play (as with the DC offset the scope kept overloading and tripping)

(Attachment Link)

As you can see not a bad square, the rise is pretty good.

(Attachment Link)

Okay now we view the top - hmm... that wasn't there before.

(Attachment Link)

In this picture I've added a positive DC offset which the square wave is on top of, as a result the square wave's amplitude is lower, as you can see - it's a lot less bad.

It's a pretty bad artifact. According to the service manual it's just a DC bias into an op-amp.

Great that those attachments didn't work when it did it that way.

BTW this is an extreme example, I had it at 6.84v offset (maxes out at 10) so it's not "terribly far" and a frighteningly large artifact but when viewing something riding on an offset that's nearby it's OK, so as long as the signal's "within view" it tends to be good.

There's a person here saying "oh that's expected behaviour" https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-anomaly-on-what-should-be-a-simple-task/?action=dlattach;attach=1167288;image - this image is not. That's terrible! I agree with OP here and is on screen!

You need to trust the scope to reproduce a signal that fits in the range accurately, there's no excuse for that!

--- End quote ---

Do you plan to actually read what people answered and explained to you?

You are overloading scope input amplifiers by several order of magnitude. Distortion you see is caused by user insisting on doing what people are telling you is wrong.

ALL of your signal has to be on screen. If you have 100 mV P-P riding on top of 10V DC offset, you can set scope to 20mv/div, set offset for 10V (if scope has that offset in that range) and nicely see signal on the screen.
Because setting offset subtracted 10V DC component form the signal and you defacto have a 100mV P-P signal left for scope to analyse.

If you put in 10V P-P into scope set to 20mv/div and use scope offset to look at top level of signal, you are shoveling 10V signal in preamp set for 800mV full range... You get overdrive....

So in short, ifm when you are setting the scope, some part of signal goes under or over visible screen, you are doing it wrong.... signal has to enter the screen from the left, and exit to the right and never go outside top or bottom. It actually can, 10-20% more but that is it...

Once you accept that, I am willing to explain why is it so. And yes, all current digital scopes,cheapest to very expensive,  from all brands do this same very thing.

--- End quote ---

Your tone is somewhat twatish there and I must point out:

Did you see the picture linked? it is entirely on the screen!

As for my screenshots, I was asked to provide them and yes we already agreed it was saturation.

Finally: there's one difference between OP and I - mine rises quickly *then drops* then rises back up.

saying real world things are not ideal (no matter how twatty or twat-free the tone isn't helpful.

2N3055:

--- Quote from: py-bb on December 28, 2022, 02:22:49 pm ---
--- Quote from: 2N3055 on December 28, 2022, 02:00:33 pm ---
--- Quote from: py-bb on December 28, 2022, 11:58:25 am ---Okay I did the experiment.

First up the full wave we're viewing. There is a 50 ohm terminator in play (as with the DC offset the scope kept overloading and tripping)

(Attachment Link)

As you can see not a bad square, the rise is pretty good.

(Attachment Link)

Okay now we view the top - hmm... that wasn't there before.

(Attachment Link)

In this picture I've added a positive DC offset which the square wave is on top of, as a result the square wave's amplitude is lower, as you can see - it's a lot less bad.

It's a pretty bad artifact. According to the service manual it's just a DC bias into an op-amp.

Great that those attachments didn't work when it did it that way.

BTW this is an extreme example, I had it at 6.84v offset (maxes out at 10) so it's not "terribly far" and a frighteningly large artifact but when viewing something riding on an offset that's nearby it's OK, so as long as the signal's "within view" it tends to be good.

There's a person here saying "oh that's expected behaviour" https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-anomaly-on-what-should-be-a-simple-task/?action=dlattach;attach=1167288;image - this image is not. That's terrible! I agree with OP here and is on screen!

You need to trust the scope to reproduce a signal that fits in the range accurately, there's no excuse for that!

--- End quote ---

Do you plan to actually read what people answered and explained to you?

You are overloading scope input amplifiers by several order of magnitude. Distortion you see is caused by user insisting on doing what people are telling you is wrong.

ALL of your signal has to be on screen. If you have 100 mV P-P riding on top of 10V DC offset, you can set scope to 20mv/div, set offset for 10V (if scope has that offset in that range) and nicely see signal on the screen.
Because setting offset subtracted 10V DC component form the signal and you defacto have a 100mV P-P signal left for scope to analyse.

If you put in 10V P-P into scope set to 20mv/div and use scope offset to look at top level of signal, you are shoveling 10V signal in preamp set for 800mV full range... You get overdrive....

So in short, ifm when you are setting the scope, some part of signal goes under or over visible screen, you are doing it wrong.... signal has to enter the screen from the left, and exit to the right and never go outside top or bottom. It actually can, 10-20% more but that is it...

Once you accept that, I am willing to explain why is it so. And yes, all current digital scopes,cheapest to very expensive,  from all brands do this same very thing.

--- End quote ---

Your tone is somewhat twatish there and I must point out:

Did you see the picture linked? it is entirely on the screen!

As for my screenshots, I was asked to provide them and yes we already agreed it was saturation.

Finally: there's one difference between OP and I - mine rises quickly *then drops* then rises back up.

saying real world things are not ideal (no matter how twatty or twat-free the tone isn't helpful.

--- End quote ---

Yes I'm a twat... Thank you... You are so kind. That comment definitely elevated this discussion.. Thank you.

This image ?

https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-anomaly-on-what-should-be-a-simple-task/?action=dlattach;attach=1167288;image

What is wrong with it?



py-bb:
Twatish is bad..... but OK

You see where it changes and is all over the place - that's what wrong with it. I can't believe you consider that OK.

2N3055:

--- Quote from: py-bb on December 28, 2022, 03:40:41 pm ---Twatish is bad..... but OK

You see where it changes and is all over the place - that's what wrong with it. I can't believe you consider that OK.

--- End quote ---

Thank you for being kind....

As for signal, that is how source signal looks. ...

bdunham7:

--- Quote from: 2N3055 on December 28, 2022, 03:58:53 pm ---As for signal, that is how source signal looks. ...

--- End quote ---

Pretty much--this was intended to be the 'good' example, but there is a small bit of settling after the large transition even with that screenshot with all of the signal on the screen.  I didn't think much of it at the time since it is so small, but there does appear to be a bit of damping/settling behavior at these slower timebases.  Others have remarked on a small 'dip' in slow square waves on this scope as well.

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