Following this question, I purchased a DSO-2090 USB oscilloscope.
When I power it up, I see lots of small fluctuations in the waveform, whether connected to nothing, a battery source, itself (small waveform generator on the back) or by shorting the ground clip.
In the screenshot above, the CH1 is connected to a small, battery powered circuit of mine. CH2 does not have the probe connected at all.
I have spoken to a colleague about this and was told that I should see a flat line so I am worried I have purchased a faulty unit.
My question is whether or not background noise like this is normal in an oscilloscope?
Edit 1
Added 1kHz waveform example as per comment:
Best Answer
As an indicator that the second capture you displayed looks normal, here's one I just made of a 1 KHz square wave, from my ELAB-080 combination instrument (dual channel DSO, 16-channel logic analyzer, arbitrary waveform generator (AWG), and dual channel power supply) which also has a vertical 8-bit resolution in its DSO section. (Note: at $495, the ELAB-080 was over your budget in your other question where I recommended the DSO-2090).
You can see the noise at the top and bottom of each square wave, which looks almost identical to your trace.