How many conductors does a 4-wire transmitter use?

How many conductors does a 4-wire transmitter use?

• A. Two.
• B. Four.
• C. Three.
• D. Five.

Answer: (B)

Four conductors are used because a 4-wire transmitter has its own power supply separate from the current loop signal. Two wires power the transmitter electronics, and two separate wires carry the 4-20 mA current loop to the controller. This separation allows independent powering and better isolation/noise performance. In contrast, a 2-wire transmitter shares the same two conductors for both power and signal, so only two wires are used. Therefore, the transmitter uses four conductors.

Four conductors are used because a 4-wire transmitter has its own power supply separate from the current loop signal. Two wires power the transmitter electronics, and two separate wires carry the 4-20 mA current loop to the controller. This separation allows independent powering and better isolation/noise performance. In contrast, a 2-wire transmitter shares the same two conductors for both power and signal, so only two wires are used. Therefore, the transmitter uses four conductors.