AiVibeHART Protocol
HART (Highway Addressable Remote Transducer) is a digital communication protocol for process instruments that superimposes a low-level digital signal on the 4–20 mA analogue loop, allowing configuration, diagnostics and extra variables over existing wiring.
HART uses frequency shift keying based on the Bell 202 standard, representing binary ones and zeros as two frequencies superimposed on the loop current. Because the digital signal averages to zero, it does not disturb the analogue measurement, which remains the primary process value. Communication is master-slave: a host such as a handheld communicator, asset management system or HART-enabled I/O card queries the device for its primary variable, secondary variables, configuration and status.
HART is widely used in the process industries because it works with the large installed base of 4–20 mA instruments and wiring. Technicians use it to commission and calibrate transmitters, read diagnostics from valve positioners and verify device configuration. Asset management software can monitor device health continuously through HART multiplexers or HART-capable I/O. WirelessHART, standardised as IEC 62591, extends the protocol to mesh radio networks.
The protocol is maintained by the FieldComm Group. Its digital data rate is low, so it suits configuration and diagnostics rather than fast control, and multidrop mode connects several devices on one pair but gives up the analogue signal. Loop resistance requirements must be met for communication to work. Changing the configuration of a live instrument can affect control and safety functions, so it must follow site procedures and be carried out by qualified personnel.
Key points
- Digital FSK signal superimposed on the 4–20 mA analogue loop
- The analogue value remains the primary measurement
- Used for commissioning, calibration and device diagnostics
- Maintained by the FieldComm Group
- WirelessHART, standardised as IEC 62591, extends it to mesh radio
Where AiVibe comes in
AiVibe designs and manufactures the AiAmbA AI Factory, whose edge devices and AI agents let people talk to PLC, CNC and robot controllers in plain language. Agents only propose changes, a trained operator confirms each one, and the AI Factory never replaces a machine's control or safety systems.