ABB AC500-S Safety User Manual page 303

Configuration and programming
AC500-S Libraries > SafetyBlocks_PLCopen_AC500_v22.lib
Fig. 109: Timing Diagrams for SF_GuardMonitoring
External signals: Mechanical setup combines that of an opening and closing switch according to EN 954
(safety guard with two switches). Discrepancy time monitoring for time lag between both mechanical
switches reaction, according to EN 954 (to be considered as "application error" detection, i.e., generated by
the application).
An error is detected if the time lag between the first S_GuardSwitch1/S_GuardSwitch2 input and the second
is greater than the value for the DiscrepancyTime input. The Error output is set to TRUE.
The function block detects a static TRUE signal at the RESET input.
Error and Reset Behavior
The S_GuardMonitoring output is set to FALSE. If the two S_GuardSwitch1 and S_Guardswitch2 inputs are
bridged, no error is detected. To leave the Reset error state, the Reset input must be set to FALSE. To leave
the discrepancy time errors, the inputs S_GuardSwitch1 and 2 must both be set to FALSE.
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