Signal Filtering - Siemens SINAMICS G120 Operating Instructions Manual

8.10.4

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.
Figure 8-26
The filter does not increase the inverter response time. The inverter activates its safety
functions as soon as one of the two F-DI signals changes its state from high to low.
SINAMICS G120C Inverter
Operating Instructions, 01/2011, FW 4.4, A5E02999804A AB
Filter for suppressing discrepancy monitoring
8.10 Fail-safe function Safe Torque Off (STO)
Functions
231