8 AI thermocouple / RTD — hazloc-rated end-of-life module
The Siemens SM 331 analog input module 6ES7331-7SF00-0AB0 provides 8 analog inputs that can be configured as thermocouple inputs (types B, E, J, K, N, R, S, T, U, L) or as resistance thermometer inputs (Pt100, Pt200, Ni100). This module carries ATEX II 3 G (2) GD Ex nA [ib Gb] [ib IIIC Db] IIC T4 Gc and FM Class I, Division 2, Groups A, B, C, D T4 approvals, confirming it is suitable for installation in Zone 2 gas and Zone 22 dust hazardous areas (ATEX) and Class I Div 2 locations (FM). The ATEX marking includes intrinsic safety entity parameters for the connected field circuits.
Thermocouple and RTD input flexibility with mV ranges
For thermocouple inputs, the module supports millivolt ranges from -25 mV to +25 mV, -50 mV to +50 mV, -80 mV to +80 mV, -250 mV to +250 mV, and -500 mV to +500 mV, as well as a ±1 V range. This covers the full output span of common thermocouple types including the low-level signals from Type T and Type E at cryogenic temperatures. Resistance thermometer inputs (Pt100, Pt200, Ni100) are supported via 4-wire connection for Pt100 and Pt200, eliminating lead resistance error. The module does not provide channel-to-channel isolation, so the common-mode voltage on all inputs must remain within the module's rated limits. The maximum shielded cable length is 200 meters for thermocouple inputs and 50 meters for resistance thermometer inputs. This constraint should be factored into field wiring plans to avoid signal degradation.
End-of-life sourcing — order against RFQ
For replacement planning, verify that any alternative module in the S7-300 family supports the same thermocouple types and RTD configurations, and confirm the ATEX/FM hazardous-area approvals match your installation requirements.