Scope channel Noise difference?

[Wmacky]

That was very helpful.  Thanks for taking the time to do that! 

I really just wanted to make sure this brand new scope was not to far from the norm for these units. This last post gives me some comfort.


As to calibration. Yes, that was tried early on. No dice!

[miguelvp]

Did you calibrate it after say, 20 minutes? because on boot it takes a while to settle.
Of course when you power it up it will be off but will get to the calibrated state after several minutes.

If you calibrate right after powerup it will tend to drift and be off after being on for a while.

Edit: Still the voltage drift and settle time might annoy some but the purpose for the scope is about timing accuracy.

[tautech]

Did you calibrate it after say, 20 minutes? because on boot it takes a while to settle.
Of course when you power it up it will be off but will get to the calibrated state after several minutes.

If you calibrate right after powerup it will tend to drift and be off after being on for a while.

Edit: Still the voltage drift and settle time might annoy some but the purpose for the scope is about timing accuracy.

Yes, but since the very first oscilloscope settling time has been well known.
Componentry takes time to fully reach a temperature where results are consistant.

Most if not all Service manuals specify a mimimun time powered on before calibration adjustments are made.
A similar time is usually also stated in the manual before a "Self Cal" is done.

All this is well known by experienced users but catches newbies out.

[Wmacky]

Yep, I calibrated dead cold.     I just did it again after a warm up. Live and learn.  Unfortunately no change.

BUT!   I did somewhat resolve my issue.  I downgraded the scope to 200 MHZ.  At that bandwidth the channel noise difference Vpp AVERAGED is only 60uV!  And. it looks prettier on the screen @ 500uV P/D.


YeaH, I know.  I haven't done anything but knock off a grand of value from the scope. But, it doesn't piss me off as much now when I look at it.  Perhaps I should forget about it? Unless someone thinks that's a mistake and it's with returning. I PMed Dave and hope for his comment. I'd love to learn if he gives it a thumbs up or swift kick!

[rs20]

BUT!   I did somewhat resolve my issue.  I downgraded the scope to 200 MHZ.  At that bandwidth the channel noise difference Vpp AVERAGED is only 22uV!  And. it looks prettier on the screen @ 500uV P/D.

Reducing bandwidth reduces peak-to-peak/RMS noise, because you're filtering away some of the noise. This isn't surprising, and Dave's done a video about it (under the guise of explaining why digital scopes appear noisier). The scope also has hi-res and averaging acquisition modes which will reduce the noise a whole lot more, without compromising bandwidth. How often do you plan to use the scope at the most sensitive voltage setting?

YeaH, I know.  I haven't done anything but knock off a grand of value from the scope. But, it doesn't piss me off as much now when I look at it.

All I can say is: an oscilloscope is a tool, not a work of art. What you've written above is profoundly irrational.

[Wmacky]

BUT!   I did somewhat resolve my issue.  I downgraded the scope to 200 MHZ.  At that bandwidth the channel noise difference Vpp AVERAGED is only 22uV!  And. it looks prettier on the screen @ 500uV P/D.

Reducing bandwidth reduces peak-to-peak/RMS noise, because you're filtering away some of the noise. This isn't surprising, and Dave's done a video about it (under the guise of explaining why digital scopes appear noisier). The scope also has hi-res and averaging acquisition modes which will reduce the noise a whole lot more, without compromising bandwidth. How often do you plan to use the scope at the most sensitive voltage setting?

YeaH, I know.  I haven't done anything but knock off a grand of value from the scope. But, it doesn't piss me off as much now when I look at it.

All I can say is: an oscilloscope is a tool, not a work of art. What you've written above is profoundly irrational.

I was trying to be humorous I guess. So is it your suggestion that the scope should stay?  Nobody has really stated what they would do in my shoes. Again, I'm rather new to this, and appreciate the experience of others more familiar......

[rs20]

I was trying to be humorous I guess. So is it your suggestion that the scope should stay?  Nobody has really stated what they would do in my shoes. Again, I'm rather new to this, and appreciate the experience of others more familiar......

My 2c: when I look at those maximum-vertical-zoom, non-bandwidth-limited, no-averaging, no-hi-res screenshots, they both look terrible. Superimpose a signal of interest on top of that, and it's going to be a horrible experience trying to sort the signal from the noise. This isn't a fault with the scope, you've just put it in the worst case position. If you look at how the noise is 1.5mV or whatever at 300 MHz, that's extraordinary performance for the price point (maybe, I dunno). Set it back to 1V/div, and it'll look perfect.

What you're doing is taking a race car, driving it around an oily hairpin bend at 300 miles per hour and complaining that the tyres have slightly different lack of grip while you smash into the railings. Turn on averaging or hi res, orset it to 1 V/div, and forget about this "problem". Is my very long 2c.

If your scope has significantly (2x) worse noise than another copy of the same model, then that's a different story.

[JohnnyBerg]

So is it your suggestion that the scope should stay?  Nobody has really stated what they would do in my shoes. Again, I'm rather new to this, and appreciate the experience of others more familiar......

My advise would be to return the scope. You clearly do not know how to operate it, and what its for. What use is a tool, if you do not now what to do with it?

Why did you buy it in the first place, and why 300 MHz? I guess just because it was shinny. You obviously have no idea what to do with that.

[Wmacky]

So is it your suggestion that the scope should stay?  Nobody has really stated what they would do in my shoes. Again, I'm rather new to this, and appreciate the experience of others more familiar......

My advise would be to return the scope. You clearly do not know how to operate it, and what its for. What use is a tool, if you do not now what to do with it?

Why did you buy it in the first place, and why 300 MHz? I guess just because it was shinny. You obviously have no idea what to do with that.

Thanks for the smug comment, ( not the first),  and the discouragement of someone that wants to learn. I hope this was able to provide you with a superiority fix.

"Why did you buy it in the first place"          Because I enjoy building Vacuum tube audio amps, and would like to learn to use a Oscilloscope to troubleshoot them. I have other interests as well, such as drone assembly, video flown RC aircraft, amateur radio, and general electronic interests. "Shinny" wasn't a reason I used.

I thank everyone else that took the time to comment.

[JohnnyBerg]

So is it your suggestion that the scope should stay?  Nobody has really stated what they would do in my shoes. Again, I'm rather new to this, and appreciate the experience of others more familiar......

My advise would be to return the scope. You clearly do not know how to operate it, and what its for. What use is a tool, if you do not now what to do with it?

Why did you buy it in the first place, and why 300 MHz? I guess just because it was shinny. You obviously have no idea what to do with that.

Thanks for the smug comment, ( not the first),  and the discouragement of someone that wants to learn.I hope this was able to provide you with a superiority fix.

I thank everyone else that took the time to comment.

I posted pictures and measurements from my scope. Others told you that the channel difference was insignificant. That there is a relation between bandwidth and noise.

And then you pop that rather silly question, and got a straight, direct answer.

What did you expect to hear?

[dom0]

I don't think JohnnyBerg meant to insult you (per se), but rather your choice of tools. Powerful tools usually require equally knowledgeable and powerful users (except for handguns which are safe for everyone) so you're probably better off with a less powerful tool (e.g. less of that noisy bandwidth which you apparently don't need anyway), which is then simpler to use and thus can be put to better use by you. Alternatively, get more knowledgeable about your tools, that works too, but takes time ;-)

[JohnnyBerg]

I don't think JohnnyBerg meant to insult you (per se),

I certainly do not mean to insult anyone. English is not my native language and I find it difficult to express myself in the right tone 

but rather your choice of tools. Powerful tools usually require equally knowledgeable and powerful users (except for handguns which are safe for everyone) so you're probably better off with a less powerful tool (e.g. less of that noisy bandwidth which you apparently don't need anyway), which is then simpler to use and thus can be put to better use by you. Alternatively, get more knowledgeable about your tools, that works too, but takes time ;-)

+1

[T3sl4co1l]

(except for handguns which are safe for everyone)

Spoken like a true 'Murkan!

JK, I don't mean to insult you

Tim

[Wmacky]

I don't think JohnnyBerg meant to insult you (per se),

I certainly do not mean to insult anyone. English is not my native language and I find it difficult to express myself in the right tone 

but rather your choice of tools. Powerful tools usually require equally knowledgeable and powerful users (except for handguns which are safe for everyone) so you're probably better off with a less powerful tool (e.g. less of that noisy bandwidth which you apparently don't need anyway), which is then simpler to use and thus can be put to better use by you. Alternatively, get more knowledgeable about your tools, that works too, but takes time ;-)

+1

Perhaps I overreacted, but the intent of the phrase "I guess just because it was shinny."  seemed clear enough to me?