Siemens Simatic M7-400 Reference Manual page 301

5.19.2 Measuring Methods and Measuring Ranges of the
SM 431; AI 8
Measuring Methods
You can set the following measuring methods for the input channels:
• Voltage measurement
• Current measurement
• Resistance test
• Temperature measurement
You specify the setting by means of the measuring range modules on the module
and by means of the "Measuring Type" parameter in STEP 7.
Circuit Variants for 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 5-52 Selection of the Measuring Method for Channel n and Channel n+1 of the SM 431;
AI 8 14 Bit
Meas. Method Disa-
Chan. n+1
bled
Meas. Method
Channel n
Disabled x
Voltage x
Current four-wire x
transmitter
Current two-wire x
transmitter
Resistor x
four-conductor
Resistor x
three-conductor
Thermal resistor x
four-conductor
Thermal resistor x
three-conductor
Thermocouples x
Example
If you select "current (two-wire transmitter)" for channel 6, you can then only
deactivate the measuring method or set "current (two-wire transmitter)" for
channel 7.
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
14 Bit
Voltage Current Current
4-DMU 2-DMU
x x x
x
x
x
x
Analog Modules
R-4L R-3L RTD-4L RTD-3L TC-L
x
x
x
5-85