Which of the following is a symptom of a ground loop?

Which of the following is a symptom of a ground loop?

• A. Offset signals
• B. Ground fault
• C. Stable readings
• D. Proper shielding

Answer: (A)

Ground loops create a difference in electrical potential between the transmitter’s return path and the control system ground. That extra potential acts like an additional voltage in the loop, which in a 4–20 mA system shows up as a DC offset in the current. In other words, the process value might be correct, but the loop current is shifted, producing offset signals. A ground fault would be a direct short to ground, not just a shifted reading; stable readings imply little interference, and proper shielding reduces interference rather than producing a symptom.

Ground loops create a difference in electrical potential between the transmitter’s return path and the control system ground. That extra potential acts like an additional voltage in the loop, which in a 4–20 mA system shows up as a DC offset in the current. In other words, the process value might be correct, but the loop current is shifted, producing offset signals. A ground fault would be a direct short to ground, not just a shifted reading; stable readings imply little interference, and proper shielding reduces interference rather than producing a symptom.