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9.8.5.4
Input filter
Overview
The input filter suppresses unwanted brief signal changes at a fail-safe digital input (F-DI).
Requirement
Unexpected movements due to long connecting cables
If a cable at a fail-safe digital input is too long, the fail-safe digital input might not reliably detect
a short-circuit of the connecting cable to 24 V or to ground. An undetected short-circuit may
mean that the connected sensor is no longer working. This may impair the functional safety of
the machine or the system and therefore endanger people or lead to material damage.
• Only connect cables with a length of ≤ 30 m to a fail-safe digital input.
Description of function
If a fail-safe digital input (F-DI) is connected to an electromechanical sensor, for example, then
contact bounce leads to brief signal changes. In this case, an immediate response of the
converter to signal changes is not desirable. Too many signal changes within a specific time
result in a converter fault.
During the filter time (p10017) of the input filter, the converter ignores signal changes. The
input filter time is fixed to 4 ms.
The set input filter impacts the response time of the safety function connected to the F-DI.
9.8.5.5
Self-test of the fail-safe digital input (F-DI)
Overview
To detect faults at an early stage, the converter tests its shutdown paths, functions and
interfaces using the online self-test.
Self-test with internal test signals is available to test a fail-safe digital input (F-DI).
Description of function
The self-test checks with test signals at the input terminals of the F-DI whether the F-DI can be
switched to the fail-safe state (to "low"). If the converter does not detect a feedback signal, then
it triggers a fault response.
The converter internally generates test signals for the input circuit of the F-DI (p10041 = 0).
The test signal length and the test cycle cannot be changed.
SINAMICS S200 pulse train servo drive system with SIMOTICS S-1FL2
Operating Instructions, 11/2023, FW V6.3, A5E51646767B AA
WARNING
9.8 Safety Integrated (for S200 PTI only)
Functions
289
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