What are the four wires in a 4-wire transmitter?

What are the four wires in a 4-wire transmitter?

• A. Two for the output signal and two for the shield.
• B. One for power and three for data.
• C. Two for power supply and two for the output signal.
• D. Four for ground connections.

Answer: (C)

The main idea is that a four-wire transmitter has separate paths for power and signal. Two wires provide the power to the transmitter’s electronics, giving it a stable independent supply. The other two wires carry the 4–20 mA output current, which is the actual measurement signal sent to the controller or receiver. Keeping these paths separate improves noise immunity and allows the transmitter to be powered independently from the signal loop. The shield or ground is not counted as part of the four wires, and isn’t the signal path itself.

The main idea is that a four-wire transmitter has separate paths for power and signal. Two wires provide the power to the transmitter’s electronics, giving it a stable independent supply. The other two wires carry the 4–20 mA output current, which is the actual measurement signal sent to the controller or receiver. Keeping these paths separate improves noise immunity and allows the transmitter to be powered independently from the signal loop. The shield or ground is not counted as part of the four wires, and isn’t the signal path itself.