What baud rate is typical for HART digital communication?

• A. 300 baud
• B. 1200 baud
• C. 4800 baud
• D. 9600 baud

Answer: (B)

HART digital communication rides on the same 4–20 mA loop by modulating the current with two tones in a frequency-shift keying scheme. The rate at which those digital bits are carried is 1,200 bits per second, so the typical baud rate for HART data is 1,200. This value reflects a practical balance: it’s fast enough to transfer useful diagnostic and device data in a reasonable time, yet slow enough to keep the digital channel from distorting the analog 4–20 mA signal over typical field cables and loop conditions. Higher speeds would require more bandwidth and could complicate compatibility with older field devices, while much slower speeds would make communications and diagnostics impractically slow. So 1,200 baud is the standard, commonly cited rate for HART digital communication.