Rockwell Automation 1756-XXXX ControlLogix Digital I/O Modules - Manual (Page 75)

Rockwell Automation Publication 1756-UM058G-EN-P - November 2012 75
Diagnostic Module Features Chapter 4
Features Specific to
Diagnostic Output Modules The table below lists features specific to ControlLogix diagnostic digital output
modules.
Field Wiring Options
As with diagnostic input modules, ControlLogix diagnostic output modules
provide isolated or nonisolated wiring options. I/O modules provide point-to-
point, group-to-group, or channel-to-channel wiring isolation.
Your specific application determines what type of isolation is necessary and
which output module to use.
No Load Detection
For each output point, no load detection senses the absence of field wiring or a
missing load from each output point in the Off state only.
The output circuit on a diagnostic output module has a current sensing
optoisolator used in parallel with the output transistor. Current flows through
this sensing circuit only when the output is Off, as shown in the simplified
diagram.
Topic Page
Field Wiring Options 75
No Load Detection 75
Field-side Output Verification 76
Pulse Test 78
Diagnostic Change of State for Output Modules 79
IMPORTANT Although some ControlLogix diagnostic I/O modules provide nonisolated,
field-side wiring options, each I/O module maintains internal electrical
isolation between the system side and field side.
Current
Sense
Load
V+
41681
Output
Transistor
Current Flow with
Output Off
Current Flow with
Output On