Industrial Engineer · phase 2 of 16
Two-Wire Transmitter
Analog transmitter powered through the same current loop that carries its measurement signal.
The Explain card
- Plain English
- A two wire transmitter runs on the same pair of wires that carry its signal. The loop current powers the electronics and reports the measurement at the same time.
- Example
- A pressure transmitter has just two terminals. The analog input card, or a separate loop supply, pushes 24 V into the loop and the transmitter regulates the current between 4 and 20 mA.
- Why it matters
- Two wires mean cheaper runs and fewer terminals, and the transmitter cannot draw below 4 mA because it needs that much to stay alive. A loop that reads zero is broken, never merely at the bottom of scale.
- Hook
- The signal wire is the power cord.
Where it sits in the deck
Phase 2: PLC I/O and Field Signals
Where the controller meets the machine: discrete and analog signals, the wiring conventions behind them, and the field devices that send them.
