My understanding of the cause of common mode noise in my measurement

[eTobey]

Hi,

i have read a bit, drawn my circuit and started thinking. Because i did not comprehend why the noise was exactly generated in the scope/circuit, even though i had the probe shorted.

Now i have come a conclusion and would like to know if this is true, and if there are other circumstances where this would be not the case or somehow different:
"The noise is generated by a current that flows through the GND lead of the probe (through earth GND back to the supply and its parasitic capacitances), and therefore creating a voltage."

[m k]

Practically everything is an antenna of some sort.
So everything must be filtered somehow also.

If your shorted probe is showing a shape of a line voltage it is not shorted to neutral.

[eTobey]

If your shorted probe is showing a shape of a line voltage it is not shorted to neutral.

Neutral? You mean earth ground?

[m k]

More like a point the PSU treats as neutral.
It can still be "far" from real earth.

When you short the probe you still have a triangle of probe leads and a circuit at the other end.

Some say that for 4-wire measurement you should have all leads disconnected from the bundle.
I guess that starts to be around a magic category.