Siemens Simatic M7-400 Reference Manual page 313

Circuit Variants of the Channels
Two channels are set in each case with the measuring range module. There are
therefore restrictions as regards the measuring method for the adjacent channels
0/1, 2/3, 4/5 and 6/7, as shown in the following table:
Table 5-58 Selection of the Measuring Method for Channel n and Channel n+1 of the SM 431; AI 8
Bit (6ES7 431-1KF20-0AB0)
Meas. Type
Channel n+1
Meas. Type Chan-
nel n
Disabled
Voltage "1 V
Voltage 1 to 5 V
Voltage "10 V
Current four-wire
transmitter
Current two-wire
transmitter
Resistance
four-conductor
Example
If you select "current (two-wire transmitter)" for channel 6, you can only disable the
measuring method or set "current (two-wire transmitter)" for channel 7.
Circuit for Resistance Measurement
The following conditions apply when measuring the resistance with the SM 431;
AI 8 x 14 Bit:
Table 5-59 Channels for Resistance Measurement of the SM 431; AI 8
Measuring Type Parameter
Resistor
(four-conductor terminal)
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Disabled Voltage Voltage
"1 V
1 to 5 V
x x
x x
x
x
x
x
x
Permissible
for Channel n
0, 2, 4 or 6 You must disable the( "Measuring Type" parameter for
channels n+1 (1, 3, 5, 7).
The reason The connections of channel n+1 are used
to supply the resistance that is connected to
channel n.
Voltage Current
"10 V
4-DMU
x x x
x x
x x
x
14 Bit (6ES7431-1KF20-0AB0)
Condition
Analog Modules
14
Current R-4L
2-DMU
x
x
5-97