4 source inputs for the ET 200S slice
The Siemens 6ES7131-4BD51-0AA0 is a 4-channel digital input module for the ET 200S distributed I/O system, delivering four 24 V DC source inputs in a 15 mm-wide housing. It ships as a 5-unit pack — the packing unit is part of the order code, so one order line lands five identical modules, which is the standard way to stock this spare part for line-side cabinets.
Signal thresholds and sensor compatibility
The input stage recognises a logic '1' at -15 to -30 V and a logic '0' at -5 to +30 V — the negative-going signal range means this module expects sourcing (PNP) sensors that pull the input to the negative rail when active. Each channel draws about 7 mA at 24 V when on, and the module supports 2-wire proximity sensors with a permissible quiescent current up to 1.5 mA, so it won't false-trigger on the leakage of a standard inductive prox.
Input timing and cable runs
The hardware debounce filter is fixed — not parameterisable — with a typical on-delay of 3 ms and a spread of 2 ms to 4.5 ms for both rising and falling edges. That 3 ms floor means the module filters out contact bounce and short sensor glitches, but it also sets the minimum pulse width the downstream PLC logic sees. For cable runs, unshielded twisted-pair is good up to 600 m; shielded cable extends that to 1 000 m, which covers most plant-floor drops from the ET 200S interface module.
Power budget and isolation
The module draws up to 500 mA from the 24 V DC backplane supply, with a typical power loss of 0.7 W — that 500 mA is the ceiling for the module plus its connected sensors, so the upstream ET 200S power module must have headroom for this slice. Channel-to-backplane isolation is tested at 500 V DC, but there is no channel-to-channel isolation, no diagnostics function, and no group-error LED. For applications that need per-channel fault reporting, this is not the module; for simple dry-contact or proximity monitoring where a green per-channel status LED is enough, it fits cleanly.