Siemens SIMATIC S7-400 Reference Manual page 258

Analog modules
5.21 Analog input module SM 431; AI 8 x 14 Bit (6ES7431-1KF20-0AB0)
● Voltage
● Current
● Resistance
Permissible input voltage for voltage input (destruction
limit)
Permissible input current for current input (destruction
limit)
Sensor connection
● For voltage measurement
● For current measurement
● For resistance measurement
● Load of 2-wire transducer
258
– As 2-wire transducer
– As 4-wire transducer
– With 2-wire connection
– With 3-wire connection
– With 4-wire connection
± 1 V / 100 kΩ
± 10 V / 100 kΩ
1 to 5 V / 100 kΩ
± 20 mA / 50 Ω
4 to 20 mA / 50 Ω
0 to 600 Ω / 10 MΩ
Maximum 18 V continuous;
75 V for 1 ms (cycle clock ratio 1 : 20)
40 mA continuous
Possible
Possible
Possible
Possible; line resistance is also measured
Possible
Maximum 750 Ω
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08