Description of the signal filter
The following filters are available for the fail-safe digital inputs:
● One filter for the simultaneity monitoring
● A filter to suppress short signals, e.g. test pulses.
Set the discrepancy time for the simultaneity monitoring.
The inverter checks that the two input signals of the fail-safe digital input always have the same
signal state (high or low).
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 permanent discrepancy signifies a fault in the fail-safe digital
input circuit, e.g. wire breakage.
When appropriately set, the inverter tolerates brief discrepancies.
The discrepancy time does not extend the inverter response time. The inverter selects its safety
function as soon as one of the two F-DI signals changes its state from high to low.
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Figure 5-4
Simultaneity monitoring with discrepancy time
Filter to suppress short signals
In the following cases, an immediate inverter response to signal changes of the fail-safe digital
inputs is not desirable:
● If a fail-safe digital input of the inverter is interconnected with an electromechanical sensor,
signal changes can occur due to contact bounce.
● In order to identify faults due to short-circuit or cross faults, several control modules test
their fail-safe digital outputs with "bit pattern tests" (bright/dark test). If a fail-safe digital
input of the inverter is interconnected with a fail-safe digital output of an open-loop control
module, then the inverter responds with a bit pattern test.
The typical duration of the signal change within a bit pattern test:
– On test: 1 ms
– Off test: 4 ms
If the fail-safe digital input responds to many signal changes within a certain time, then the
inverter responds with a fault.
Commissioning
5.11 Setting basic functions
Safety Integrated - SINAMICS G110M, G120, G120C, G120D and SIMATIC ET 200pro FC-2
Function Manual, 01/2017, FW V4.7 SP6, A5E34261271B AD
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