Rockwell Automation Publication 1734-UM013N-EN-P - September 2017 27
Safety Inputs, Safety Outputs and Safety Data Chapter 2
Figure 5 - Test Pulse in a Cycle
For the 1734-IB8S module, the pulse width (X) is typically 525 μs; the pulse
period (Y) is typically 144 ms.
When the external input contact is closed, a test pulse is output from the test
output terminal to diagnose the field wiring and input circuitry. By using this
function, short-circuits between inputs and 24V power, and between input signal
lines and open circuits can be detected.
Figure 6 - Short-circuit between Input Signal Lines
IN+
24V
24V
0V
COM
T0
T1
IN0
IN1
External Contact
Short-circuit between Input Signal Lines and Power
Supply (positive side)
External Contact
Short-circuit between Input Signal Lines
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