Define HART?

HART is an acronym for “Highway Addressable Remote Transducer”. The HART protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA as shown in fig. This enables two-way field communication to take place and makes it possible for additional information (tag numbers, measured variables, range & span data) beyond just the normal process variable to be communicated to/from a smart field instrument.

The HART protocol communicates at 1200 bps without interrupting the 4-20mA signal and allows a host application (master) to get two or more digital updates per second from a field device. As the digital FSK signal is phase continuous, there is no interference with the 4-20mA signal.