Floating ground

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A floating ground circuit is a circuit in which the ground is not used as a fixed reference, rather, it is a common node in the circuit. This can occur when equipment is not connected to a grounding point. Some older electronic equipment may be designed purposely with floating grounds. (it is not uncommon to find old vacuum tube guitar amps with this problem).

Floating grounds can become a hazard both to other electrical equipment and operators. If a person is in contact with both the equipment and a real ground point, they may act as a conductor and can be electrocuted. Ground loops can form when equipment with floating grounds are connected to properly grounded equipment, and results in a current traveling between the two devices.