Hi All
First of all thank you all for spending the time to help me! After the feedbacks around the noise, I decided to take some measurements, did comparisons and checked manuals.
Back to my original question, my goal is to determine whether or not there was something wrong with the analog oscilloscope and the way it was plotting things with the probe set to 10x attenuator.
I think the answer is: there is absolutely nothing wrong with the oscilloscope and the way its displaying the wave. In fact it is showing a very slightly clearner wave than the digital oscilloscope (probably due to its analog nature). Let me know if you agree to my statement after my analysis below.
Noise: I connected both oscilloscopes to the function generator. It is turned on, but the output for the channel is DISABLED so there is only 1V DC output there (no wave, just a flat DC signal).
Check the screens below. Both scopes are displaying the signal with the same settings. The vertical scale is currently at 100mV. You can see that in both scopes the trace is taking almost 2 divisions. In the digital I added AC RMS measure as well as P-P. The AC RMS is showing 52mv variation which make sense.
If I then turn on the signal, we can see that the wave is displayed consistently on both scopes (they both still have same settings).
Now what was making the two scopes show different lines before was the bandwidth limiting setting which was turned ON in the digital scope (my bad). What that does is to limit the bandwidth to 20mhz on the channel removing high frequency noise from the signal. In the same manner the Zoom feature of the 2225 also limits the bandwith (to 5mhz), thus removing the noise.
With that we have the screens below:
Sweet! So everything is allright with the scope, and I got Nothing to worry. Plus a learned quite a lot in this analysis.
Now, I could just have said it was all about the BW limit feature, but I really wanted to show the full analysis because now the questions are:
- Is the amount of noise I'm seeing too much?
- What would be the expected noise that I should see?
I tested the AC RMS on the probe adjust signal on both scopes and they are quite similar (50 in the digital and 60 in the analog).
If I short the probe on the digital oscilloscope I get 12mv reading on the AC RMS, significant smaller.
Thanks!
Walter