How much scope noise is to much

crutschow

Joined Mar 14, 2008
26,814
What does the trace look like at the same sensitivity with the scope input grounded.
That's the intrinsic noise of the scope.

Digital scopes tend to have a higher level of noise than an analog scope.
 

rsjsouza

Joined Apr 21, 2014
293
Whatever @crutschow mentioned with a remark: digital scopes are capable of showing spurious noise more evidently than analog scopes (this due to phosphor persistence) but not necessarily have more noise.

I would refer to two videos from Dave Jones about this subject
 

DickCappels

Joined Aug 21, 2008
7,181
Welcome to digital scopes. Yes, the noise you are seeing is quantization noise. For each measurement the scope must choose between two values, and with 8 bits it look a bit noisy. If you scope can average or integrate over a number of samples, that can be made to look a lot cleaner. Yours was my firs concern upon buying a digital scope nearly 20 years ago, but it was never a problem for me.
 

tautech

Joined Oct 8, 2019
196
I'm new to the digital scope world. I've attached a photo showing a trace obtained on a tektronic tds520.
200mv range from the onboarding squarewave generator 1.1 probe

1st photo is full bandwidth 2nd is 20mhz

Is this an acceptable amount of noise on the squarewave?
Do you mean the probe compensation output ?
While it's not intended for use with a 1x probe for other than a sanity check the noise you see is entirely normal as others have indicated.
Other than using Averaging and/or in some scopes HiRes/ERES can also be used to display waveforms with less internal noise making its way to the display.
 

Thread Starter

condenser

Joined Nov 13, 2017
16
What does the trace look like at the same sensitivity with the scope input grounded.
That's the intrinsic noise of the scope.

Digital scopes tend to have a higher level of noise than an analog scope.
It's about the same with the probe grounded..
Just odd after looking at analog scopes for many years. Needed something faster, perhaps not as fast as I now have, but i don't expect I'll need to buy again. At least not for awhile
Thanks for everyone's input.
 
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