THREE WIRE LOW POWER TRANSMITTER

摘要

A three wire transmitter bidirectionally communicates AC signals to and from a first external device and sends DC signals to a second external device. The transmitter includes a sensor circuit and a communication circuit, both energized from power and common terminals of the transmitter. The communication circuit receives a sensor output indicating a sensed process variable and provide DC and AC signals to a signal terminal which connects to both external devices, and also receives AC signals from the first external device. The DC signal is representative of the sensed process variable and the AC signal is digitally representative of the sensed process variable and of transmitter data selected by the received AC signal.