USER MANUAL Manual

Introducing Block I/O
Chapter 1
1-4
Figure 1.2
Sinking
Input Example
dc Power
Supply
Field
Device
Field
Device
Sinking
Input
+V
V
10826I
Block I/O
Sourcing outputs have the power bussed in the block. When the output is
on, current is supplied to the field control device, which sinks the current.
The field circuit and the equipment remain at ground potential until the
output is turned on. Refer to Figure 1.3.
Figure 1.3
Sourcing
Output Example
dc Power
Supply
Field
Device
Field
Device
+V
V
Bus
Fuse
Fuse
10827I
Block I/O
The 1791-IOVW block uses sourcing inputs and sinking outputs.
In sourcing input modules (Figure 1.4), the +V on dc circuits is bussed on
the module supplying (sourcing) the current for each input circuit. The
field device switches the circuit to the common (side of the power supply,
sinking the circuit and causing current to flow from the module’s input