How can ground loops be prevented?

How can ground loops be prevented?

• A. Use a single, thick shield throughout the system.
• B. Ground shields at one point, use isolators, avoid tying commons together unnecessarily.
• C. Tie all commons together at multiple points.
• D. Increase shield length to reduce interference.

Answer: (B)

Ground loops happen when there are multiple return paths to ground, which lets a small current circulate and inject noise into the signal. To prevent this in a 4–20 mA/HART setup, ground the cable shield at a single point so shield currents don’t create an unwanted loop. Use galvanic isolation between devices to break direct ground connections, and avoid tying common grounds together at more than one point. This approach minimizes the loop area and stops stray currents from flowing through the measurement path, keeping the signal clean. Grounding the shield at both ends or making the shield thicker doesn’t solve the problem and can even encourage circulating currents; tying commons at multiple points introduces additional ground paths that form loops; increasing shield length generally increases susceptibility to interference. So the combination of single-point shield grounding, isolation, and minimal common grounding is the effective way to prevent ground loops.

Ground loops happen when there are multiple return paths to ground, which lets a small current circulate and inject noise into the signal. To prevent this in a 4–20 mA/HART setup, ground the cable shield at a single point so shield currents don’t create an unwanted loop. Use galvanic isolation between devices to break direct ground connections, and avoid tying common grounds together at more than one point. This approach minimizes the loop area and stops stray currents from flowing through the measurement path, keeping the signal clean. Grounding the shield at both ends or making the shield thicker doesn’t solve the problem and can even encourage circulating currents; tying commons at multiple points introduces additional ground paths that form loops; increasing shield length generally increases susceptibility to interference. So the combination of single-point shield grounding, isolation, and minimal common grounding is the effective way to prevent ground loops.