What components make up a typical control loop in instrumentation, and what are common color codes for field wiring?

• A. A loop consists of sensor, transmitter, power supply, and interconnecting cables; typical color codes: +24 V supply (red), 0 V (black/blue), shield green or bare; grounding/shielding depends on standards.
• B. A loop is only the wire from transmitter to controller; colors red/black.
• C. A loop includes sensor and controller; colors yellow for power.
• D. A loop requires separate battery; colors green for supply.

Answer: (D)