Safety
Fail-Safe Systems
A5E00085588-03
7-9
Basic Procedure
To configure the monitoring times, proceed as follows:
1. Configure the standard or fault-tolerant system. You can find the necessary
information in the relevant hardware manuals and online help systems.
2. Configure the specific monitoring times of the F-system with regard to
availability: The times should be considerably longer than the minimum
monitoring times. You can find approximation formulas in the information on
calculating the minimum monitoring times or in the Excel table
STEP7\S7BIN\S7ftimeb.xls.
3. Use the Excel table STEP7\S7BIN\S7ftimeb.xls to calculate the maximum
response time, and check whether the maximum fault tolerance time for the
process has been exceeded.
!
Safety Note – Pulse Detection
To enable pulses to be detected reliably, the time between two signal changes
(pulse duration) must be longer than the corresponding monitoring time.
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