Rockwell Automation 1747-L40 SLC 500 Fixed Hardware Style - Manual (Page 65)

Chapter 5
Wiring Your Control System
5–2
Contact Output Circuits Ċ AC or DC
Relays can be used for either AC or DC output circuits and accommodate
either sinking or sourcing field devices. These capabilities are a result of the
output switch being a mechanical contact closure, not sensitive to current
flow direction and capable of accommodating a broad range of voltages.
This high degree of application flexibility makes contact output modules
very popular and useful in control environments with a broad mix of
electrical I/O circuit requirements.
Solid-State DC I/O Circuits
The design of DC field devices typically requires that they be used in a
specific sinking or sourcing circuit depending on the internal circuitry of the
device.
Sourcing Device with Sinking Input Module Circuit
The field device is on the positive side of the power supply between the
supply and the input terminal. When the field device is activated, it sources
current to the input circuit.
DC POWER
SUPPLY
+
_
FIELD DEVICE
Input
DC Com
DC
INPUT
CIRCUIT
I