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HART

Highway Addressable Remote Transducer - hybrid analog+digital protocol for process field instruments.

Type: Hybrid ProtocolSpeed: 1200 bps (digital)Released: 1986Organization: FieldComm Group
1.2 kbps
Bandwidth
15 (multidrop), 1 (analog+digital)
Max Nodes
3000m
Max Distance
No
Real-Time

Protocol Overview

Highway Addressable Remote Transducer - hybrid analog+digital protocol for process field instruments.

When to Use HART

Choose HART for process instrument integration, upgrading analog systems, or when remote configuration and diagnostics are needed without new wiring.

Technical Specifications

Physical Layer

  • Physical Layer: FSK over 4-20mA
  • Cable Type: Standard 4-20mA wiring
  • Topology: Point-to-point, Multidrop
  • Power Over Cable: Yes

Data Layer

  • Data Link: Master/Slave
  • Encoding: FSK (1200 Hz / 2200 Hz)
  • Error Detection: Parity and checksum
  • Frame Size: Variable

Performance

  • Scan Time: 2-8 updates per second
  • Deterministic: No
  • Real-Time: No

Certification

  • Certification Required: Yes
  • License Cost: FieldComm Group membership
  • Version: HART 7

Advantages & Disadvantages

Advantages

  • ✓Works over existing 4-20mA wiring
  • ✓Backward compatible with analog systems
  • ✓Extensive device diagnostics
  • ✓Remote configuration
  • ✓Process and status information
  • ✓Huge installed base
  • ✓No additional wiring needed
  • ✓Intrinsically safe capable

Disadvantages

  • ✗Very slow (1.2 kbps)
  • ✗Not suitable for closed-loop control
  • ✗Limited to process instruments
  • ✗Multidrop loses analog signal
  • ✗Communication overhead

Common Use Cases & Applications

Process instrumentation
Pressure and temperature transmitters
Flow meters
Level sensors
Analytical devices
Valve positioners

Industry Adoption

Adoption LevelVery High
Market Share40M+ installed devices
Geographic PresenceWorldwide
Primary Industries
Oil & GasChemicalPetrochemicalPharmaceuticalWater Treatment

Supported Message Types

Universal commands
Common practice commands
Device-specific commands

Supported PLC Brands

Emerson
Endress+Hauser
ABB
Yokogawa
Siemens
Honeywell
Schneider Electric

Quick Links

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