industrial//instrumentation//HART

**Highway Addressable Remote Transducer** superimposes a digital signal on a traditional 4-20 mA loop. The analog current still carries the primary variable; the digital layer carries configuration, diagnostics, secondary variables and device identification.

Highway Addressable Remote Transducer superimposes a digital signal on a traditional 4-20 mA loop. The analog current still carries the primary variable; the digital layer carries configuration, diagnostics, secondary variables and device identification.

It let plants modernize instrumentation without replacing the wiring: the same two wires, the same PLC analog input for the process value, and a digital conversation for everything else. That is why it was central in the transition from purely analog to intelligent instruments in the 1990s.

A 1998 HART transmitter is exactly the kind of device a gateway still has to translate today, next to Modbus meters and PROFIBUS devices (edge gateway).