Using I/O on the S7-400H
7-24
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Redundant analog input modules with non-redundant sensors
Analog input modules in a 1-out-of-2 configuration are used for non-redundant
sensors:
U
R
Analog input modules
Analog input modules
I
Voltage measurement
IIndirect current measurement
Analog input modules
I
dirDirect current measurement
Figure 7-10 Fault-tolerant analog input modules in a 1-out-of-2 configuration with one sensor
Pay attention to the following when connecting a sensor to several analog input
modules:
• Connect the voltage sensors in parallel to the analog input modules (left in
illustration).
• You can convert a current into voltage using external impedance to enable you
to use voltage analog input modules connected in parallel (right in illustration).
• 2-wire transducers are powered externally to enable you to repair the module
online.
The use of redundant fail-safe analog input modules increases their availability.
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”.
Redundant analog input modules for voltage measurement
Module not suitable for voltage measurement with non-redundant encoder:
AI 4x15bit Ex 6ES7 331-7RD00-0AB0 I-Input
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