Valve position switch wiring in PLC
Advantage: If a wire breaks, indication of that position is lost. If a valve in the beam path is open and the open wire breaks, the PLC will indicate that the valve is not open. The beam would be turned off. Fail Safe
Disadvantage: If work is being performed on the valve and the +24 vdc is shorted to ground, indication of all other inputs powered by the same fuse will be lost.
Advantage: If a wire breaks, indication of that position is lost. If a valve in the beam path is open and the open wire breaks, the PLC will indicate that the valve is not open. The beam would be turned off. Fail Safe
Advantage: If work is being performed on the valve and the +24 vdc is shorted to ground, indication for only that valve is affected.
Disadvantage: Extra components to install and check. Added costs for installation