Siemens 6ES7431-1KF20-0AB0 SIMATIC S7-400 SM 431 8AI 14-Bit U/I/R Analog Input Module

The Siemens 6ES7431-1KF20-0AB0 is a SIMATIC S7-400 SM 431 analog input module with 8 isolated channels that accept voltage, current, or resistance signals at up to 14-bit resolution. Four of the eight channels also support resistance-type transmitters, and the module draws its load voltage from a separate 24 V DC supply with reverse-polarity protection.

Technical Specifications

Selection Notes

Choose this SM 431 variant when the application needs resistance-type transmitter inputs alongside voltage and current, since only 4 of its 8 channels support resistance measurement while all 8 handle voltage or current. The internal/external potential separation between channels and the backplane bus keeps measurement loops isolated from the S7-400 backplane, which matters when sensors share a common ground with other plant equipment. For applications needing higher resolution or thermocouple inputs instead, the 16-bit SM 431 variants in the same family are the better fit.

Applications

The 8-channel input count and mixed voltage/current/resistance ranges suit process signals from pressure transmitters, flow meters, and resistance-based sensors feeding an S7-400 rack. The 52 µs basic conversion time and parameterizable integration time let the interference frequency suppression be matched to 50 Hz or 60 Hz mains.