Siemens SIMATIC S7-400H - Fault-Tolerant Digital Input Modules in a 1-Out-Of-2 Configuration; Using Redundant Digital Input Modules with Redundant Sensors

Using I/O on the S7-400H
7-20
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Using redundant digital input modules with redundant sensors
You install digital input modules with redundant sensors in a 1-out-of-2
configuration:
Digital input modules
Figure 7-8 Fault-tolerant digital input modules in a 1-out-of-2 configuration with 2 sensors
The use of redundant sensors increases their availability. Discrepancy analysis
detects all errors – except for the failure of a non-redundant on-load voltage
supply. You can further increase the availability by installing redundant on-load
voltage supplies.
When connecting a sensor to several digital input modules, the redundant modules
have to have the same reference potential.
Connection examples are available in Appendix F and in the SIMATIC FAQs at
http://www.siemens.com/automation/service&support under the
keyword “Redundant I/O”.