What are the advantages of 2-wire transmitters?

• A. They require more power supplies for each sensor.
• B. Lower wiring cost, fewer conductors, good noise immunity, reliable for long cable runs.
• C. They always output a voltage signal.
• D. They cannot operate in hazardous areas.

Answer: (B)

2-wire transmitters are powered from the same current loop that they use to send the measurement, so only two conductors are needed for each device. This loop-powered arrangement reduces wiring costs and the amount of copper and terminals you must install, which is a big practical advantage in field setups with many sensors.

Because the transmitter modulates the current (4–20 mA) rather than a voltage signal, the system gains noise immunity and remains robust over long cable runs. Current signaling is less affected by voltage drops along the wire, so measurements stay reliable even as distance increases, and electromagnetic noise is less likely to distort the signal.

In addition, you don’t need a separate power supply for each sensor; a single loop power can feed many devices, simplifying installation and maintenance, especially in remote or hazardous-area installations when approved safety barriers are used.

The other statements don’t fit because a 2-wire device does not require extra power supplies, it outputs current rather than a fixed voltage, and with proper safety approvals, it can operate in hazardous areas rather than being excluded from them.