HART Protocol

Industrial/ICS 🏭 • Protocols 🔗 Difficulty: premium

Definition

HART (Highway Addressable Remote Transducer) overlays a digital FSK signal on the 4–20 mA analog loop to configure, diagnose, and read multiple variables from smart field instruments without disrupting the primary control signal.

Examples

  • A technician connects a handheld communicator to a pressure transmitter’s loop to change damping and range while the 4–20 mA output keeps the loop in control.
  • An asset management system uses a HART multiplexer to pull device diagnostics and alert maintenance when a valve positioner reports excessive travel.

Discover 🔎

HART lets you talk to smart instruments over the same two wires carrying the analog 4–20 mA signal. The analog current still drives the control loop, while a low-amplitude digital signal rides on top to read variables, check health, and change configuration. This dual-nature design made HART the de facto standard for brownfield upgrades—adding intelligence without rewiring plants.

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