Are there are other ways in which 60hz can get into a system other than ground loop ?


Yeah lot's of ways. Besides those already listed...

If there is a cylindrical inductor in the circuit. (loops can be other than in just the ground line.)

Room lights sometimes.. though more often this is capacitive coupling from florescent lights and at ~20-50kHz.

Vibration (usually at 120 not 60Hz... I assume harmonics are included.)

The best way to check is to move your circuit around. And see what happens. Things get worse as you move toward the source, inductive things will have an orientation dependence. you can block electrostatic things.

At the ridiculously low sub microvolt level, I've seen capacitve coupling between wires carrying power to different circuit fragments. (Though this was not 60Hz.)



Radiation/EMI, capacitive crosstalk, unintended magnetic coupling, power supply ripple...

  • \$\begingroup\$ Aside from power supply ripple, are these sources generally within close proximity to a system/pcb/circuit ? \$\endgroup\$ – efox29 Oct 23 '14 at 6:48
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    \$\begingroup\$ Could you expand a bit on this answer? \$\endgroup\$ – clabacchio Oct 23 '14 at 9:34
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    \$\begingroup\$ @Clabaccio: Yes, but I choose not to. \$\endgroup\$ – EM Fields Oct 23 '14 at 10:45
  • \$\begingroup\$ @efox29: It depends on what you consider to be "close proximity" and on the source. \$\endgroup\$ – EM Fields Oct 23 '14 at 10:50
  • \$\begingroup\$ Electric and/or magnetic fields will be present throughout a building and within quite a few yards of an overhead cable. You tell me whether that counts as "close proximity"... \$\endgroup\$ – user_1818839 Oct 23 '14 at 11:30

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