Noise Signal?

Question

I am working on a circuit board. I am wondering what are the possible objects that creates a 60Hz noise interference.

Answer 1

Every electrical line, connection, poor connection, wire, switch and appliance in the power distribution system

Answer 2

There are really only two sources:

Your power supply or other external connection
AND
"loops" in your circuit that can pick up 60 Hz by induction from all the 60Hz EMF that is everywhere in populated electrified areas (note, 50Hz in some areas!)

Good power supplies are filtered and don't pose a problem. Other sources need to be addressed on a item by item basis.

Good design avoids loops, but good shielding can also go a long way to eliminate Electromagnetic interference.

Answer 3

The primary causes are ground loops.

E.G. A power amp is plugged in one socket. An effects pedal is plugged into another. A grounded shield lead connects the output of the effects pedal to the amplifier input.

There is a big loop of ground along the lead, the power cable of the amp, through the power cabling back to the switch box, back to the socket where the pedal is plugged in, to the pedal and back to the lead.

The 60 Hz power signal is picked up by this loop like an antenna and so there is a 60Hz signals running around the loop.

When your signal is referenced to ground, you're going to hear the 60Hz signal that is picked up by the loop.

Answer 4

ur oscilloscope itself