What is a Ground Loop?

• A. A voltage difference that occurs between 2 grounding points
• B. A loop used to connect grounds
• C. Noise picked up by ground wires
• D. A protective earth fault

Answer: (A)

Ground loops happen when equipment is tied to more than one ground reference, forming a conductive loop. Each ground path has some impedance, so the different grounding points can sit at slightly different voltages. When devices share signal or power grounds, a voltage difference exists around the loop, and small currents circulate through the loop. These circulating currents produce noise or hum in the system and can affect measurement accuracy. The essential description is a voltage difference between two grounding points. It’s not simply a loop used to connect grounds, nor merely noise picked up by ground wires, and it isn’t a protective earth fault. Mitigation comes from grounding practices that keep grounds at a common potential, like single-point or star grounding, good shielding, or isolation where needed.