what is the difference about HART, and 4-20mA signal?
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Answer Posted / khaled khreim
The HART Protocol is an acronomy of Highway Adressable
Remote Transducer,it uses the frequancy shift koeying
standard to impose digital communication on top of the 4-
20mA signal.
this enables a two way field communication to take place,
making it possible for additional info rather than the
process variable only.
Hart protocol is a Master/Slave protocol, the HART protocol
can be used in different modes like point to point or
multidrop for communicating info from/to smart fiel device
and the controller, the field device and the controller
should be HART enabled.
In general HART protocol opens two communication channels:
the first one is the 4-20mA normal signal for the measured
value using the 4-20mA current loop. And the second chanel
is the digital signal whic is imposed on the analog one.The
digital signal gives additional info about the field device
such as device status, diagnosis, and other types of info
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