What this module is — and what it is for
The Siemens 6ES7231-7PB22-0XA8 is an analog input module from the SIMATIC S7-200 CN family, specifically the EM 231 spare part that works only with the S7-22X CPU. It carries two analog inputs designed for resistance thermometers (Pt100, Pt200, Pt500, Pt1000, Pt10000, Ni100, Ni120, Ni1000, Cu10) and plain resistance measurement up to 150, 300, or 600 ohm. Resolution reaches 16 bit with overrange (15 bit + sign), giving 0.1 °C or 0.1 °F per step on temperature types.
Key ratings that govern fit
The module fits the S7-200 CN backplane and draws 1.8 W from the bus, plus 1 mW for the sensor excitation — a light load that leaves headroom for other modules in the rack. Physical footprint is 71.2 mm wide, 62 mm deep, and 80 mm tall, consistent with the standard EM form factor. Critically, this part carries CE approval only; no UL or CSA marks are on file, so if your panel requires those for the local inspection, plan for a documented risk assessment or a separate compliance path.