Besides 4-20 mA, what outputs are common for 4-wire transmitters?

• A. Binary encoded pulses.
• B. Digital RS-232.
• C. 1-5 VDC or ±10 V analog.
• D. AC 60 Hz sine wave.

Answer: (C)

When a transmitter is 4-wire, it often provides a voltage output in addition to the current loop. This is because many control and data-acquisition systems have high-impedance analog inputs that directly measure DC voltages, making interface simple and straightforward. The most common voltage ranges are 1-5 V DC or ±10 V DC, which give enough dynamic range for accurate measurement while staying easy to interface with typical ADCs.

Why this fits well: 1-5 V or ±10 V voltages provide a direct, stable representation of the sensed value that can be fed into a voltage input without needing current-to-voltage conversion at the receiving end. The transmitter is usually powered separately (hence “4-wire”), so it can deliver a clean voltage signal as an additional option to the standard 4-20 mA loop.

The other possibilities described are not typical outputs for this scenario: binary encoded pulses or RS-232 are digital communication methods, not a continuous analog measurement signal. An AC 60 Hz sine wave would not represent a single measurement value in a simple, linearly scalable way.