Rockwell Automation Publication 1734-UM013J-EN-P - July 2014 39
Safety Inputs, Safety Outputs, and Safety Data Chapter 2
Safety Outputs (1734-OB8S)
Read this section for information about safety outputs.
Safety Output with Test Pulse
When the safety output is on, the safety output can be configured to pulse test
the safety output channel. By using this function, you can continuously test the
safety output’s ability to remove power from the module’s output terminals. If an
error is detected, the safety output data and individual safety output status turn
off.
Figure 18 - Test Pulse in a Cycle
For the 1734-OB8S module, the pulse width (X) is typically 475 μs; the pulse
period (Y) is typically 575 ms.
Dual-channel Mode
When the data of both channels is in the on state, and neither channel has a fault,
the outputs are turned on. The status is normal. If a fault is detected on one
channel, the safety output data and individual safety output status turn off for
both channels.
Figure 19 - Dual-channel Setting (not to scale)
To prevent the test pulse from causing the connected device to malfunction,
pay careful attention to the input response time of the output device.
ON
OFF
OUT0
Safety Output
0, 1
Status
OUT0
OUT1
OUT1
Safety Output
0, 1
Status
Fault Detection
Error
Detected
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Normal Operation
Safety
I/O
Network
Data Sent
to the
Controller
Safety
I/O
Network
Data Sent
to the
Controller
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