Functions
7.10 Safe Torque Off (STO) safety function
Inverter with CU240B-2 and CU240E-2 Control Units
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Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
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Figure 7-23 Connecting an F digital output module, e.g. SIMATIC F digital output module
You can find additional connection options and connections in separate control cabinets in
the Safety Integrated Function Manual, see Section Overview of documentation (Page 13).
7.10.4
F-DI signal filtering
The inverter checks the signals of the fail-safe digital input for consistency. Consistent
signals at both inputs always assume the same signal state (high or low).
Discrepancy
With electromechanical sensors (e.g. emergency stop buttons or door switches), the two
sensor contacts never switch at exactly the same time and are therefore temporarily
inconsistent (discrepancy). A long-term discrepancy points toward a fault in the wiring of a
fail-safe input, e.g. a wire break.
An adjustable filter in the inverter prevents faults caused by temporary discrepancy. Within
the filter tolerance time (parameters p9650 and p9850), the inverter suppresses the
discrepancy monitoring of the fail-safe inputs.