Answer / ayaz

250 ohm  use in loop only for hart protocol and use only smart devices 

Answer / ashraf

According to the HART Foundation spec, the 1200-2400 Hz HART signal needs a minimum (230 ohm) resistance in the loop to create a HART signal with enough amplitude to meet the sensitivity requirements of a HART modem receiver.

Answer / hitesh

convert analog signal 4-20mA to digital signal 1-5V

Answer / nitesh kumar

For converting 4-20 mA 

Answer / nilesh66in

The power supply is a low impedance to the hart signal
shorting it out. Adding the resistor raises the impedance
so that the signal can be detected by the calibrator. The
HART protocol uses 1200 baud Frequency Shift Keying (FSK)
based on the Bell 202 standard to superimpose digital
information on the conventional 4 to 2OmA analog signal.


Nilesh Bhagwat ( Sr. Inst Tech)

Answer / ritesh patel

convert output of digital to analog

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