Galvanically (that is, optically or electromagnetically) isolated 4- to 20-mA current loops offer robust noise immunity and tolerate long cable runs. These advantages, combined ...

Consequently, a 4- to 20-mA current is drawn from the out terminal of VR1 and circulated in the output loop. The full-scale 20-mA output is trimmed via R1. The impedance of the low-pass filter ...