Siemens SIMATIC S7-400 Reference Manual page 263

Circuit for resistance measurement
The following conditions apply when measuring the resistance and temperature with the SM
431; AI 8 x 14 Bit:
Table 5-56 Channels for resistance measurement of the SM 431; AI 8 x 14 Bit (6ES7431-1KF10-0AB0)
Measuring type parameter
Resistance
(4-conductor connection)
Unused channels
Unused channels can be left open. Set the measuring range modules to position "B". You can
improve the noise immunity of the module in a measuring environment with serious
interference by interconnecting M- and M
Measuring ranges
Set the measuring ranges using the measuring range modules, and at the "measuring method"
parameter in
Table 5-57 Measuring ranges of the SM 431; AI 8 x 14 Bit (6ES7431-1KF10-0AB0)
Selected measuring
method
V: Voltage
2DMU: Current
(2-wire transducer)
4DMU: Current
(4-wire transducer)
R-4L: Resistance
(4-conductor connection)
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
5.21 Analog input module SM 431; AI 8 x 14 Bit (6ES7431-1KF20-0AB0)
Permissible for
channel n
0, 2, 4 or 6
STEP 7 .
Measuring range
(type of sensor)
± 1 V
1 to 5 V
± 10 V
4 to 20 mA
4 to 20 mA
± 20 mA
600 Ω
You must disable the "Measuring type" parameter for channels n+1
(1, 3, 5, 7).
Reason: The connections of channel n+1 are used to supply the
resistance that is connected to channel n.
.
ANA
Measuring range module set‐
tings
A
B
D
C
A
Analog modules
Condition
Description
The digitized analog values are lis‐
ted in the section "Representation of
analog values for analog input chan‐
nels" in the voltage measuring
range.
To supply these transducers with
current you must connect 24 V to the
L+ and M front connector terminals.
The digitized analog values are lis‐
ted in the section "Representation of
analog values for analog input chan‐
nels" in the current measuring range.
The digitized analog values are lis‐
ted in the section "Representation of
analog values for analog input chan‐
nels" in the current measuring range.
The digitized analog values are lis‐
ted in the section "Representation of
analog values for analog input chan‐
nels" in the resistance measuring
range.
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