What are common outputs of 4-wire transmitters?

• A. 4-20 mA, 1-5 VDC, or ±10 V analog.
• B. Only 4-20 mA.
• C. Voltage outputs only.
• D. 4-20 mA, 1-5 VDC, or ±10 V analog.

Answer: (D)

Four-wire transmitters are designed to offer flexible signal outputs because their separate power supply lets the transmitter generate different types of signals. The most common is the 4-20 mA current loop, which is highly robust over long cables and in noisy environments. But many transmitters can also provide voltage outputs, such as 1-5 V DC or even bipolar ±10 V, to match systems that expect voltage inputs or higher-impedance ADCs. Because these devices can be configured to drive either current or voltage signals, the broadest, most accurate statement about common outputs includes all three: 4-20 mA, 1-5 VDC, or ±10 V analog. The options that limit outputs to only current or only voltage miss the versatility these transmitters can offer.