What are ground loops?
Whenever more than one current path exists between two points, a ground-loop is set up, and if the two points are at different potentials (which is nearly every case), circulating ground currents will flow. Basically, ground-loops cause problems by adding and subtracting current or voltage from the signal source. As a result, the receiving device can’t differentiate between the wanted and the unwanted signals. The biggest source of ground-loop interference, and why two points, reputed to be ground, can be at different potentials, is ground inductance. Inductance becomes the common coupling mechanism that forces all, or a portion, of the signal return current to share a return path with the interference source. The interference source can be due to noise generated internally, within the instrumentation enclosure, or by external interference sources. The long ground loops associated with industrial sensor applications can conduct noise current because of external magnetic fields that pas
