4–20 mA Current Loops

A transmitter, shielded twisted pair, 24 VDC loop supply and PLC/DCS/RTU AI module, with RL(max) = (Vsupply − Vmin) / 0.020 A (900 Ω at 24 V and 6 V minimum), a signal level table (4 mA = 0%, 20 mA = 100%, below 3.6 mA = fault per NAMUR 43), wiring practices, applications and a field loop check.