Four inputs that handle AC or DC, 24 to 48 V
The 6ES7131-4CD02-0AB0 is a 4-channel digital input module for the ET 200S distributed I/O system. Each channel accepts 24 V to 48 V UC (universal current), meaning the same module handles AC or DC signals without rewiring — useful when a panel mixes 24 VDC sensors and 48 VAC limit switches on the same slice. The input thresholds are defined for both voltage types: a logic 1 is detected at 15 V to 57.6 V DC or 15 V to 48 V AC, while logic 0 sits at -6 V to +6 V DC or 0 V to 5 V AC. That gives a clean noise margin on 24 V nominal circuits and still reads a 48 V signal correctly without a divider network.
Diagnostics and protection per module
This module includes parameterizable diagnostics — the red SF (group error) LED lights on wire break or short circuit. The wire-break detection circuit sources a minimum load current of 0.5 mA to 2 mA through the sensor; if the quiescent current drops below that threshold, the module flags the channel. A fixed current-limiting resistor (18 kΩ at 24 V, 39 kΩ at 48 V) prevents the wire-break sense current from falsely triggering on a healthy 2-wire sensor. Short-circuit protection is provided per module, and reverse-polarity protection is automatic for both AC and DC supplies — the module handles a reversed 24 VDC or 48 VAC connection without damage.
DIN-rail footprint and backplane loading
Unshielded cable runs up to 600 m; shielded runs reach 1 000 m. The input filter is fixed at 15 ms for both on-to-off and off-to-on transitions — adequate for industrial sensors but worth noting if your application needs sub-10 ms response to fast edges.