What is HART Communications Protocol?
HART technology is based on a master or slave protocol in which HART-enabled master devices (host devices) communicating with HART-enabled devices. It was developed as a proprietary digital communications protocol in 1986 by Rosemount Inc. (or you can regard it as Emerson Inc.). As we all know, HART is an open protocol so that any manufacturer or freely employed user can use it for free.
Hart can use 4-20 mA system without interrupting the 4-20 mA analog signal on digital communication. When the analog signal continues to provide the original value to the field meter, the digital signal provides additional device information. This makes it possible to communicate bi-directional fields, rather than just passing the normal process variables to additional information in the Field tool, like sensors, transmitters, and other devices that collect data or perform tasks. This allows the Hart users to use the 4-20 mA signal excellent system and also want a "smart" protocol.
It’s said that more than 70% of all “smart” process instruments support HART communication and HART Protocol is the most widely available digital communications standard in the field of process control surely.
All in all, HART communication protocol is an excellent protocol and technology inside field devices.