The Siemens 6ES7231-5QD50-0XB0 is a signal board for the S7-1200 G2 CPU family, adding 4 thermocouple inputs directly on the CPU's front slot. It accepts type J or K thermocouples and includes onboard cold-junction compensation, so no external reference junction or isothermal block is needed. Thermocouple signal levels are in the millivolt range – keep TC wire routed away from VFD and high-current power wiring. The board's cold-junction compensation is reliable with a clean signal path; noise on the TC pair will show up as temperature drift that looks like a field issue.
Occupies one signal board slot on the S7-1200 G2 CPU, directly plugging into the front connector. No additional DIN-rail space required – the board mounts flush with the CPU face. Packaged singly (82 x 34 x 79 mm). Panel builders: account for the board's terminal height when closing the cabinet door – typical SB clearance matches the CPU's own depth, but verify against field wiring duct placement.