What is the recommended practice for terminating shielded cables?

• A. Do not ground the shield at all.
• B. Ground the shield at the device only.
• C. Ground the shield at one end or both ends as EMI conditions require; use proper connectors.
• D. Ground the shield at the power source only.

Answer: (C)

Shielding works by giving EMI a low-impedance path to ground, so the shield must be bonded to ground at the termination. The best practice is to ground the shield at one end or at both ends as EMI conditions require, and to use proper shield-termination connectors that keep the shield continuous and firmly bonded to the equipment ground. Grounding at a single end can minimize ground-loop currents in some installations, while grounding at both ends can improve shielding effectiveness on long or highly EMI-prone runs, provided the grounding scheme is designed to avoid problematic loops. Leaving the shield ungrounded defeats its purpose, and grounding only at the device or only at the power source can leave shielding incomplete or introduce unwanted currents.