Achievable Safety Classes with F-I/O
5.2 Safety Functions for Achieving Safety Classes for F-I/O with Inputs
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05
5-3
Effect of Sensor Quality on Safety Class
The achievable safety class is dependent on the quality of the sensor and the magnitude of
the proof-test interval in accordance with IEC 61508 (interval for external function test).
If the quality of the sensor is lower than the quality stipulated in the required safety class,
redundant sensors connected via two channels must be used.
See also
1oo2 Evaluation for F-I/O with Inputs (Page 5-5)
5.2.1
1oo1 Evaluation for F-I/O with Digital Inputs
Introduction
This section presents examples for wiring of sensors to provide a better understanding of the
1oo1 evaluation. The examples, taken from the
Automation System S7-300 Fail-safe Signal
Modules manual, show several options for wiring sensors to F-SMs.
1oo1 Evaluation
In the case of 1oo1 evaluation, a nonredundant sensor is connected via one channel to the
F-module.
Burner Management Applications in Accordance with VDE 0116 and EN 298
If sensors that afford safety via one channel in accordance with VDE 0116 and EN 298 are
used, S7-300 F-SMs, ET 200S and ET 200pro F-modules, and ET 200eco I/O modules with
digital inputs may be used with 1oo1 sensor evaluation in burner management applications
in accordance with VDE 0116 and EN 298.
Example: One Single-channel Sensor Connected via One Channel to One F-DI (SIL2/Category 3)
The following figure presents the wiring diagram for an SM 326, DI 24 ☓ 24 VDC with 1oo1
sensor evaluation. The sensor is supplied by the F-I/O. This wiring enables SIL2/Category 3
to be achieved. SIL2/Category 3 can only be achieved if a suitably-qualified sensor is used.
/
0
',
9V
60
',['&9
Figure 5-1
Example: Wiring Diagram for One Sensor Connected via One Channel to One F-DI
(1oo1)
