Rockwell Automation Publication 440R-UM013E-EN-P - March 2017 45
Chapter 7
EMD Safety Relay Timing Functions
The EMD safety relay has three functions that use timing:
• Off delay
•On delay
•Jog
The off-delay timing depends on whether the function is retriggerable.
During the timing cycle, the Logic IN status indicator flashes.
Off Delay, Non-retriggerable
With input B1 open, the off-delay function is not retriggerable. The off-delay
timer starts when the logic link signal at terminal L12 turns off. Once started,
the off-delay timer runs for its full duration. Figure 32
shows three cases of the
timing sequences that can occur with this configuration.
Figure 32 - Off-delay, Non-retriggerable Timing Diagram
Case 1
1. The logic link signal at terminal L12 turns on and the safety outputs
turn on immediately (that is, within the specified reaction time).
2. The logic link signal turns off and the off-delay timer starts.
3. The off-delay time has elapsed, and the safety outputs turn off.
L12
Safety
Outputs
Fault
t t t
1
Case 1 Case 2 Case 3
2 3 4 5 6 7 8 9 10 11 12 13 14
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