What is the HART protocol and what is it for?

What is the HART protocol and what is it for?

19 Jan 2020

With the end of World War II and the fall of important geopolitical barriers, the world entered a new technological era. At this time, the approximation of science with the industrial activity allowed the rapid development and absorption of cutting-edge technologies in all the productive stages of the industry, an event that became known as the third industrial revolution. It was in this context that, in 1989, the HART protocol appeared. Acronym for Highway Addressable Remote Transducer, the protocol was created to facilitate the calibration, as well as the range and damping adjustments of analog equipment.

Protocol features and benefits

Commonly used for communication between intelligent field devices and a control system, HART was the first digital bidirectional communication protocol that did not affect the analog control signal. It provides two simultaneous communication channels: a 4-20mA analog signal and a digital signal. The analog signal transmits the measured variable (in the case of a field instrument) using a 4-20mA loop, while the digital signal is used to carry additional information from the device, such as configuration standards, calibration, parameterization, descriptive TAGs, among others.

HART can be used in applications from most industry segments, even in hazardous environments. The protocol operates according to the Master-Slave standard, where the slave will only transmit a message if there is a request from the master, which means that the field instrument (slave) will only send information when it receives a request from the control system (master).

In terms of performance, HART the following features can be highlighted:

  • Simple design, easy to operate and maintain;
  • Compatibility with analog instrumentation;
  • Analog signal and digital communication;
  • Option of point-to-point or multidrop communication;
  • Flexible data access using up to two masters;
  • Supports multivariable equipment;
  • 500 ms response time (with up to two transactions);
  • Compatible with products and other protocols from various manufacturers.