RTD module for the S7-200 rack
The Siemens 6ES7231-7PB21-0XA0 is an EM231 RTD input module that mounts directly on the S7-22X CPU expansion bus — no separate power supply needed beyond the backplane. It provides 2 analog inputs configurable for PT100, PT200, PT500, PT1000, PT10000, Ni100, Ni120, Ni1000, Cu10, or resistance ranges of 150, 300, and 600 ohms with 15-bit plus sign resolution.
RTD types you can wire directly
The module accepts a wide range of RTD types: PT100/200/500/1000/10000, Ni100/120/1000, and Cu10, plus straight resistance measurements in 150, 300, and 600 ohm ranges. Resolution is 15-bit plus sign across the selected range, which gives you enough granularity to see a fraction of a degree on a PT100 without external signal conditioning.