Where is the shield of a shielded instrumentation cable typically grounded?

• A. Grounded at both ends
• B. Grounded at one end (usually the measurement instrument end)
• C. Not grounded
• D. Grounded at the sensor end only

Answer: (B)

Shielding works by providing a low-impedance path for interference to flow to ground, keeping the inner signal conductors quiet. Grounding the shield at only one end—usually the measurement instrument end—keeps the shield at a single reference potential and lets it drain noise without creating a loop. If both ends are grounded, tiny voltage differences between grounds can drive currents around the shield, creating a ground-loop that can introduce noise and voltage drops into the signal path. Leaving the sensor end ungrounded avoids introducing additional paths for current near the source. This one-end grounding approach is the standard practice for shielded instrumentation cables.