Siemens SIMATIC S7 - Selecting the Digital Input Application

Fail-Safe signal module (SM) applications
3.1 Digital input applications
S7-1200 Functional Safety Manual
68 Manual, 02/2015, A5E03470344-AA
3.1.1
Selecting the digital input application
Input architectures for achieving Safety Integrity Level (SIL)/Category/Performance Level (PL)
Table 3- 1 Safety Integrity Level (SIL)/Category/Performance Level (PL) requirements
Application
Sensor
supply
Sensor eval-
uation
Channel
connection
Type of sensor
connection
Achievable
SIL/Category/PL
Without
short-
circuit
detection
With short-
circuit
detection
1 and 2 Internal
or
External
1oo1 evalu-
tion
Single input 1 channel 2/3/d
3 and 4 Internal
or
External
1oo2 evalua-
tion
Two inputs 2 channel
equivalent
3/3/e
5
Internal
2 channel
equivalent
3/3/e
3/4/e
6 External 3/3/e
7
Internal
2 channel - 3 wire
non-equivalent
3/3/e
3/4/e
8 External 3/3/e
9
Internal
2 channel - 4 wire
non-equivalent
3/3/e
3/4/e
10
External
3/3/e