I see that my oscilloscope has some 50 Hz when the probe only is connected to the oscilloscope, which is normal. But I want to know if my circuit is catching the 50 Hz main from e.g. the power supply. Is there any good way of doing this?
I have a Siglent SDS 1052DL+ oscilloscope and I am measuring the output of a load cell connected to a board.
Edit: Measurements using Jerry Coffins and EforDogsFan methods.
Probe tip connected to probe GND: Showing no significant 50 Hz.
Probe tip connected to probe GND and PCB GND: Showing no significant 50 Hz. Rather some 330 kHz noise from a switching voltage regulator on the board.
Probe tip and probe GND not connected (open): Picking up significant 50 Hz noise, obviously changing in amplitude depending on how the probe wire is put on the table.
Measuring output of load cell: Showing significant 50 Hz noise compared to the DC voltage output of the load cell.
Measuring output of load cell with extra weight compared to previous measurement: Just to show the DC offset when adding significant weight.