Glossary · Industrial communication
HART protocol
Also known as: HART, Highway Addressable Remote Transducer
German: HART-Protokoll
In process automation, the HART protocol (Highway Addressable Remote Transducer) superimposes a digital frequency-shift-keyed signal on the 4–20 mA analog current loop, so that field instruments can be configured and diagnosed digitally while the analog signal keeps transmitting the process value. It is managed by the FieldComm Group.
- Industrial communication
- Standards
- Process industry
In one sentence
HART adds digital communication on top of a 4–20 mA loop, allowing configuration and diagnostics without losing the analog signal.
Example
A technician connects a handheld communicator to the loop of a pressure transmitter and changes its measuring range via HART without disconnecting the 4–20 mA signal.
How it applies
- Engineering: HART lets plants keep proven 4–20 mA wiring while gaining digital access to device data. HART-capable I/O cards or multiplexers pass the digital data on to asset management systems.
- Commissioning: Device tag, range, damping and units are set via HART. The configured range must match the scaling in the control system, or the displayed value is wrong.
- Safety: In safety instrumented systems the analog value is typically the safety-relevant signal. Write access via HART is usually restricted or protected, because an unintended parameter change can affect a safety function.
- Documentation: The documentation team lists HART commands and device variables supported, the device description version and the write protection options.
HART vs. WirelessHART
Wired HART rides on the analog loop. WirelessHART uses the HART application layer over a wireless mesh network, without a 4–20 mA signal.