Siemens SIMATIC S7-400H System Manual page 191

Library V5.x Library V4.x Library V3.x Module
Distributed: Redundant AI dual-channel
X
S7-400H
System Manual, 03/2012, A5E00267695-11
X AI8x12Bit
Use in voltage measurement
The "wire break" diagnostics function in HW Config must not be activated,

neither when operating the modules with transmitters nor when
thermocouples are connected.
Use for indirect current measurement
When determining the measuring error, observe the following: The total input

resistance in measuring ranges > 2.5 V is reduced from a nominal 100 kOhm
to 50 kOhm when operating two inputs connected in parallel.
The "wire break" diagnostics function in HW Config must not be activated,

neither when operating the modules with transmitters nor when
thermocouples are connected.
Use a 50 ohm resistor (measuring range +/- 1 V) or 250 ohm resistor

(measuring range 1 - 5 V) to map the current on a voltage, see figure 10-9.
The tolerance of the resistor must be added on to the module error.
This module is not suitable for direct current measurement.

Use of redundant encoders:
You can use a redundant encoder with the following voltage settings:

+/- 80 mV (only without wire break monitoring)
+/- 250 mV (only without wire break monitoring)
+/- 500 mV (wire break monitoring not configurable)
+/- 1 V (wire break monitoring not configurable)
+/- 2.5 V (wire break monitoring not configurable)
+/- 5 V (wire break monitoring not configurable)
+/- 10 V (wire break monitoring not configurable)
1...5 V (wire break monitoring not configurable)
13.4 Connecting redundant I/O to the PROFIBUS DP interface
Using I/Os in S7–400H
Order number
6ES7331–7KF02–0AB0
191