Simple Current-Loop Transmitter Converts PWM To 4-to-20-mA Output Nov. 20, 2000 Over long cable runs, an isolated 4-to-20-mA current loop offers robust noise immunity and tolerance.

A signal-injection circuit for control-loop analysis is flat from dc to 200 kHz, isolated from chassis ground and easily constructed with a readily available instrumentation amplifier Brian Keeney ...