Question about Ground Loops

[walid1]

Why you enlarge the problem, try to forget the datalogger for a monent, my question is very simple
i ask if you work in TV corporation and you notice that there is some bars in the picture and a hum in the audio and u want to prove to the others that there is a ground loop what you tell them and what measurement you must make to support yourself.
thanks

 

[MP1]

I do not see where sensors connected to a logger is any different than all of the different peripherals of a TV working together.
If all components do not have the same ground potential, none of your voltage references are the same from one end of the device to the other. If the shielding is not good on all points that are protected from spurious frequencies, you will have this type of noise as well. These are the two main concerns in grounding.
Normally, one goes through the system with a scope in TV equipment to see where the signal is no longer clean. Then further investigation usually provides an answer as to why.

MP