Which sequence correctly represents a simple wiring diagram linking a controller, recorder, and a valve positioner in series?

• A. Pos. of Controller -> Pos. of Recorder -> Neg. of Recorder -> Pos. of Positioner -> Neg. of Positioner -> Neg. of Controller
• B. Pos. of Controller -> Neg. of Controller -> Pos. of Recorder -> Neg. of Recorder -> Pos. of Positioner -> Neg. of Positioner
• C. Pos. of Recorder -> Pos. of Controller -> Pos. of Positioner -> Neg. of Recorder -> Neg. of Positioner -> Neg. of Controller
• D. Pos. of Controller -> Pos. of Recorder -> Neg. of Recorder -> Pos. of Positioner -> Neg. of Positioner -> Neg. of Controller

Answer: (D)

In a simple current-loop wiring, the same current must travel through every device in one continuous path and return to the source. For a controller, recorder, and valve positioner, the correct path starts at the controller’s positive, goes into the recorder’s positive, then continues from the recorder’s negative into the positioner’s positive, and finally returns from the positioner’s negative to the controller’s negative. That is: controller positive → recorder positive, recorder negative → positioner positive, positioner negative → controller negative. This creates a closed loop where all devices are in series and the current flows through each in order. Other sequences would interrupt the loop or reverse the flow through a device, so they wouldn’t provide a proper single current path.