What is HART protocol and how does it work?

HART (Highway Addressable Remote Transducer) superimposes digital communication on 4-20 mA analog signals. A 1200 Hz FSK signal carries digital data without affecting the 4-20 mA reading. This enables: device configuration, diagnostics, multi-variable data transmission, and calibration remotely. HART supports point-to-point (maintain analog output) or multi-drop (digital only, up to 15 devices). It is widely used because it works with existing 4-20 mA infrastructure. HART-IP extends the protocol over Ethernet for modern systems. Configuration requires HART communicator or PC with modem.