Practical Tips

HART Communication across the isolation distance

In addition to the analog 4…. 20 mA current signal, many 2-wire transmitters permit digital communication, which is modulated on the output current. A popular protocol is the Hart Communication of the HART Communication Foundation (

It is the function of an appropriate transmitter-repeater amplifier to also transmit the modulated frequency in unadulterated form across the isolation distance. In view of the fact that HART Communication must function in both directions, the HART transmitter repeater has a return channel which transmits the digital queries from the master to the slave (field device, transmitter) against the normal analog data flow.

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