Why should shielded cable be used in 4-20 mA loops?

Why should shielded cable be used in 4-20 mA loops?

• A. To improve mechanical durability
• B. To comply with OSHA
• C. To reduce electrical noise
• D. To increase current capacity

Answer: (C)

Shielded cable reduces electrical noise in 4-20 mA loops by blocking electromagnetic interference from affecting the signal. In a current loop, the measured value is conveyed by the loop current, and stray EMI from motors, drives, or nearby equipment can couple into the conductors and create small voltage fluctuations that distort the reading. The shield provides a conductive barrier around the signal conductors and is grounded so interference is diverted away from the loop, preserving accurate current transmission and improving reliability in noisy environments. The other options aren’t the primary purpose: shielding doesn’t mainly enhance mechanical durability, isn’t a safety or regulatory requirement, and doesn’t increase how much current the loop can carry.

Shielded cable reduces electrical noise in 4-20 mA loops by blocking electromagnetic interference from affecting the signal. In a current loop, the measured value is conveyed by the loop current, and stray EMI from motors, drives, or nearby equipment can couple into the conductors and create small voltage fluctuations that distort the reading. The shield provides a conductive barrier around the signal conductors and is grounded so interference is diverted away from the loop, preserving accurate current transmission and improving reliability in noisy environments.

The other options aren’t the primary purpose: shielding doesn’t mainly enhance mechanical durability, isn’t a safety or regulatory requirement, and doesn’t increase how much current the loop can carry.