What is a HART communicator and How it works?

What is HART Communicator?

HART communicator is a tool designed to communicate with process instruments. HART communicators use 4-20mA analog wiring to establish communication with the HART-enabled devices. HART is an open communication protocol. HART communicators are suitable for processes that demand the use of several instruments for monitoring, calibration, or for processes in which the instruments are located in hazardous regions.

A HART communicator device consists of:

  • LCD display
  • Keypad
  • Battery
  • Charging cable

Working principle of HART Communicator

HART stands for Highway Addressable Remote Transducer. To superimpose low-level digital communication signals on top of the 4-20mA signal, the HART Protocol employs the Frequency Shift Keying (FSK) standard. This enables bidirectional field communication, allowing additional information beyond normal process variables to be sent and received to and from intelligent field devices.

The HART protocol communicates at 1200 bps without interfering with the 4-20 mA signal, allowing the host application (master) to receive more than two digital updates per second from the smart field device. Because the digital FSK signal is phase-continuous, it does not interfere with the 4-20mA signal. The 4-20mA signal carries the basic measurement (for field devices) using the industry standard 4-20mA current loop, the fastest and most reliable. Additional information about a device is transmitted using a digital signal superimposed on an analog signal.

The HART protocol offers two real-time communication channels. They are

  • An analog 4-20mA signal
  • A digital signal

The digital signal provides various information about the instruments such as status of the device, diagnostics, instrument type, sensor type, model number, and so on. The two communication channels combined provide a complete, economical, and very powerful field communication solution that is easy to use and configure.

Click here to read HART communicator features and connection

What are all the capabilities of a HART Communicator?

  • The HART 375 Communicator’s primary role is to communicate with an instrument that uses the HART protocol.
  • Provide information about the instruments such as instrument type, sensor type, model number and so on.
  • Each HART instrument can be named, tagged or changed.
  • Each HART instrument’s diagnostic abnormality can be performed.
  • Adjustments for URV (Upper Range Value), LRV (Lower Range Value) are possible.
  • Can monitor variable process values and signal values in milliamperes (mA).
  • During calibration, this function can be used to reset and set the reading value.
  • Can be used to give the control valve the Auto-Manual Calibration command.
  • Can be used to calculate the Control Valve’s Equal Percentage, Linear, and Quick Opening.
  • Signal injection for simulation is possible.

HART Protocol Layers

HART is built on the essential Open System Interconnection (OSI) standard model:

HART uses three of the seven layers: the Physical Layer, the Data Link Layer, and the Application Layers.

Major HART Communicator manufacturers

  • Emerson Process Management (475 Field Communicator, AMS Trex Communicator)
  • Endress+Hauser ( Xpert SMT77, Xpert SMT70, SWA70)
  • Yokogawa ( YHC5150X, YHC4150X)
  • Fluke (Fluke 154, 709H mA)
  • Druck (DPI 620)

Advantages of HART Communicator

  • They are designed primarily for the work of field service technicians.
  • Easy to run field devices
  • Can check the status of the field device remotely.
  • We can configure the field devices remotely especially when the field device is in a Hazardous Environment.

Disadvantages of HART Communicator

  • The digital signal in the HART communicator is slow.
  • Can connect only a maximum of 16 HART devices