Answer / vaibhav v t

HART is a protocol and not a device.It is protocol for
digital signal communnication.
HART compatible transmitter transmits digiatl signal super-
imposed on analog 4-20 mA signal and gives many useful
infoarmation about the transmitter and process parameter
other than output.
You can configure the HART based transmitter using HART
configuator withou removing the trasnmitter from its
location/process.
4-20mA is simple low current signal which is propotional to
calibration range.

Answer / 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

Answer / prince

normally in industries we use 4-20mA signal to transfer the
signal from a transmitter to the control system.nowadays
the trasmitters are smart type. so a HART is a device used
to communicate with this smart transmitters to get the data
online or offline. HART is a digital device, so this
digital signal will superimpose on the analog transmiiter
signal without disturbing it.

Answer / mastersensor80

ANSWER NO 5 IS GOOD,the question about communication
prtotocol, how we trassfer the signal from transmitter to
the DCS,Many ways let us compare between two of them.
a/ 4 - 20 ma (conventila wiring)
b/ HART
HART use the 4 -20 ma but the communication is done via
digital this why we can view many of the transmitter
parameters,this base on PKS (phase hey shifting)refer to
modulation tecniques in communication.

Answer / mujahid/dinesh

HART compatible transmitter transmits digiatl signal super-
imposed on analog 4-20 mA signal and gives many useful
infoarmation about the transmitter and process parameter
other than output.
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.

Answer / haridass

HART Communicator - is a device used to communicate with
the HART / SMART family transmitters, used in the process
control.
* To monitor the PV, Current mA value, Sensor Temperature,
* It is used to re-range the transmitter,
* damping adjustment,
* trimming the sensor of zero/lower/upper ranges.
* create the tags/messages of the transmitter.
* Review the complete details of the transmitter.
* Loop testing the control loop (Indicator/Controller), etc.

Whereas the 4-20 mA source is used for the following:

* To simulate the 4-20 mA signal (For calibration of
control valves, loop testing of the closed/open loop).
* Using the high accuracy 250 ohms resistor, we can get 1-
5vdc as the output which is useful for the DCS input.

Answer / raj

HART=higely addresaable remote tranduer which works on high
frquency modulatition tech. to calbirate smart
transmitter and 4-20ma signal std.linear signal

Answer / rp

HART is a communicator/device works on RF Signal whereas 4-
20 mA is a Electrial Analog Signal not a Device/Instrument.

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