Products > Test Equipment
How much noise floor and other things matter in oscilloscope usability
<< < (7/63) > >>
Andreas:

--- Quote from: Fiorenzo on December 23, 2021, 12:00:05 pm ---In what situation really matter to have an oscilloscope with a "low" noise floor?

--- End quote ---

The most annoying situation is when you use a FFT to detect small signals within a larger complex signal.
E.g. 50 Hz mains hum within a pre-amplified signal. (AC transformer too near to the setup creating a large error nearly not visible in the time domain).

E.g. actual Chopper frequencies and overlay of different stages (dependant on temperature) at the output of a Chopper stabilized OP-Amp. (had the problem that the measured noise increased suddenly at special temperatures due to interferences)

with best regards

Andreas

Fiorenzo:

--- Quote from: Kleinstein on December 23, 2021, 12:47:34 pm ---For most uses the noise of the scope is not really an issue. This is because a 1:10 probe is often the mayjor noise source.  Unless the scope is rather high in noise, the noise floor is mainly an issue with the few measurements done with an 1:1 probe or similar signal via coax.
For digital signals itself the scopes noise is usually not an issue, but it may be when looking at the supply ripple.

For comparing the noise, one should take the bandwidth into account. With a higher BW the RMS noise naturally goes up. This effect can make a new higher BW scope look higher noise. So  one usually should compare at the same BW, like the usual 20 MHz BW setting.

2 Gs/s are a bit on the low end for 500MHz BW. This may lead to some aliasing and a few more thoughts about what one is actually seeing at the short time scale end.

--- End quote ---

Thank you Kleinstein for your reply.

What typology of circuits/signals need measurements with a 1x probe?

Does a higher sample rate give a better visual resolution of square wave signals at high frequency  or its benefit is reduced by the amount of noise of the front end?
Fiorenzo:

--- Quote from: nctnico on December 23, 2021, 01:28:17 pm ---
--- Quote from: Kleinstein on December 23, 2021, 12:47:34 pm ---For most uses the noise of the scope is not really an issue.

--- End quote ---
I strongly disagree with this. An oscilloscope with a lot of noise gives thick traces which make it hard to see the actual level of a signal. Ofcourse you can use high-res or bandwidth limiting but IMHO these should be targeted at cleaning up a signal and not masking a poorly designed analog front end. An oscilloscope with a low noise floor is easier to work with. I used to own an Agilent DSO7104A and it was just horrible to work with for analog stuff due to the massively thick traces it has due its own noise.

Also note that the noise doesn't only apply to the most sensitive V/div setting, it applies similar to all V/div settings. The noise level is usually specified in Volts using the most sensitive V/div setting but it would be more accurate to specify it as a percentage of a division or full range. In the end the V/div setting adjusts an input divider but the actual noise level (what goes into the ADC and what gets added by the ADC) stays the same; it is just scaled differenty.

--- End quote ---

Thank you, interesting.
Sighound36:
This was one fo ther main reasons for purchasing Lecroy scopes, (we also have Rigol 8000's) which are great general scopes and have some cracking features, but for low noise rail voltage measurments (and 2 channel FFT's) that are consistant, accurate (gain accuracy of 0.5%) and reliable coupled with the superb selection of probes then Wavepro HD is the R&D go to. We alosmuse powerananlysers (both DC and AC which are again very accurate) along with a 6705C.

nctnico is on the money, scope accuracy is very important imho
Fiorenzo:

--- Quote from: Fungus on December 23, 2021, 02:51:59 pm ---
--- Quote from: Fiorenzo on December 23, 2021, 12:00:05 pm ---For example the noise floor:
In what situation really matter to have an oscilloscope with a "low" noise floor?

--- End quote ---

When you're measuring very small signals.


--- Quote from: Fiorenzo on December 23, 2021, 12:00:05 pm ---I am going to use It for many different things, I am a "begginer" but I do digital stuff with embedded electronics and I also aim to learn more things as possible about analog electronics starting from working on an old valve radio that i would like to repair and experiment with.

--- End quote ---

It won't make any difference at all on your digital stuff.

For the radio? If it turns out to be a problem you can easily add a preamplifier and make it even better than a lower-noise oscilloscope.





--- Quote from: Fiorenzo on December 23, 2021, 12:00:05 pm ---So how much this matter in electronics? How this could preclude its usability?

--- End quote ---

It's not a showstopper. You can still do everything, just maybe not as easily for a few specific things.

The real questions are: How often do you do those things? How much would you have to spend to get a lower-noise 'scope with the same abilities as your Rigol? Is the extra money well-spent?

--- End quote ---

Yes I understand what you mean, but I don't have the knowledge to understand ​all the "abilities" of my scope.
My budget is <2000€ but if it is possible to spend less of 500€ It would be (offcourse) better because I could buy other equipments.
It Is a difficult decision because there are so many models of oscilloscopes and no one is perfect.
I would like to have the right instrument that will let me expand my knowledge and build circuits without particular constrains, maybe I am exagerating because I don't have a complete understanding of all the fields of electronics, but at the same time I do not expect to work with Ghz exotic electronics.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod