Highway Addressable Remote Transducer Protocol
The HART Communications Protocol (Highway Addressable Remote Transducer Protocol) is an early implementation of Fieldbus, a digital industrial automation protocol. Its most notable advantage is that it can communicate over legacy 4-20 mA analog instrumentation wiring, sharing the pair of wires used by the older system. According to Emerson, due to the huge installed base of 4-20 mA systems throughout the world, the HART Protocol was one of the most popular industrial protocols today. HART protocol made a good transition protocol for users who were comfortable using the legacy 4-20 mA signals, but wanted to implement a "smart" protocol. Industries seem to be using Profibus DP/PA and Foundation fieldbus (also by Rosemount) more as users become familiar with later technology and look to take advantage of the enhanced diagnostics they can provide.
The protocol was developed by Rosemount Inc., built off the Bell 202 early communications standard, in the mid-1980s as proprietary digital communication protocol for their smart field instruments. Soon it evolved into HART. In 1986, it was made an open protocol. Since then, the capabilities of the protocol have been enhanced by successive revisions to the specification.
Read more about Highway Addressable Remote Transducer Protocol: Modes, Packet Structure
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