Monitoring and Response Times of F-Systems
A.2 Configuring the Monitoring Times
Safety Engineering in SIMATIC S7
A-2
System Manual, 04/2006, A5E00109529-05
A.2
A.2
Configuring the Monitoring Times
Configuring the Monitoring Times for F-Systems
Monitoring times for the safety program are configured similarly in S7 Distributed Safety and
S7 F/FH Systems. That is, in some cases you enter the monitoring times as F-block
parameters and in
STEP 7 dialogs, as described in the following sections. For monitoring
communication between the F-CPU and F-I/O, you configure the monitoring times in
HW Config in the object properties dialog for the applicable F-modules, F-SMs, fail-safe
DP standard slaves or fail-safe I/O standard devices.
Rules for Configuring Monitoring Times
When configuring monitoring times, you must take into account the availability as well as the
safety of the F-system as follows:
•
Availability: To ensure that the temporal monitoring is not triggered when there is no
error, the monitoring times selected must be sufficiently long.
•
Safety: To ensure that the process safety time is not exceeded, the monitoring times
selected must be sufficiently short.
Warning
In order for pulses to be reliably detected, the time interval between two signal changes
(pulse duration) must be greater than the corresponding monitoring time.
General Procedure for Configuring Monitoring Times
Use the following procedure for configuring monitoring times:
1. Configure the standard or H-system.
Refer to the applicable hardware manuals and online help systems for needed
information.
2. Configure the specific monitoring times of the F-system with respect to availability.
Approximation formulas for calculating the minimum monitoring time are presented below
in the respective sections on monitoring times or in the following:
–
For S7 Distributed Safety an Excel calculation file is available in the Internet at:
http://support.automation.siemens.com/WW/view/en/11669702/133100
.
–
For S7 F/FH Systems: in
...\Siemens\STEP7\S7BIN\S7ftimeb.xls directory
3. Use these MS Excel files to calculate the maximum response time and ensure that the
process safety time is not exceeded. If necessary, reduce the specific monitoring times of
the F-system.
