Siemens Simatic S7-400 - Manual (Page 301)

Analog Modules
5-85
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
5.19.2 Measuring Methods and Measuring Ranges of the
SM 431; AI 8
14 Bit
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
Chan. n+1
Meas. Method
Channel n
Disa-
bled
Voltage Current
4-DMU
Current
2-DMU
R-4L R-3L RTD-4L RTD-3L TC-L
Disabled x x x x x
Voltage x x x
Current four-wire
transmitter x x
Current two-wire
transmitter x x
Resistor
four-conductor x
Resistor
three-conductor x
Thermal resistor
four-conductor x
Thermal resistor
three-conductor x
Thermocouples x x 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.