Which practice is NOT a typical EMI mitigation technique for instrumentation loops?

Which practice is NOT a typical EMI mitigation technique for instrumentation loops?

• A. Ground shields at both ends
• B. Route cables away from EMI sources
• C. Use shielded twisted pair
• D. Install line reactors

Answer: (A)

Ground shielding is most effective when it is tied to ground at a single point to avoid creating a ground loop. Ground shields at both ends can form a loop current path along the shield, and EMI can circulate in that loop or be driven into the signal conductor, adding noise to the low-level instrumentation signal. By connecting the shield to ground at only one point, you minimize those loop currents and reduce the chance that EMI will couple into the loop. The other practices are typical ways to reduce EMI in instrumentation loops. Routing cables away from known EMI sources lowers the exposure of the signal path to interfering fields. Using shielded twisted pair helps reject noise and maintain signal integrity. Installing line reactors on power feeds can dampen fast transients and limit conducted EMI that might couple into the instrumentation loop.

Ground shielding is most effective when it is tied to ground at a single point to avoid creating a ground loop. Ground shields at both ends can form a loop current path along the shield, and EMI can circulate in that loop or be driven into the signal conductor, adding noise to the low-level instrumentation signal. By connecting the shield to ground at only one point, you minimize those loop currents and reduce the chance that EMI will couple into the loop.

The other practices are typical ways to reduce EMI in instrumentation loops. Routing cables away from known EMI sources lowers the exposure of the signal path to interfering fields. Using shielded twisted pair helps reject noise and maintain signal integrity. Installing line reactors on power feeds can dampen fast transients and limit conducted EMI that might couple into the instrumentation loop.