Safety-rated PROFINET F-module for distributed I/O
The Siemens 6AG1688-3AF37-2AX0 is a PROFIsafe F-module in the SIMATIC ET 200pro family, designed for safety-related shutdown and monitoring in distributed automation. It communicates over PROFINET with IRT and MRP, so it participates in isochronous real-time motion networks and media-redundant ring topologies without a separate safety bus. The safety logic supports one SIL 3 channel (two-channel sensor evaluation) or two independent SIL 2 channels (single-channel sensors) for emergency-stop and guard-monitoring circuits. That means a single module can handle a dual-channel estop pair or two separate single-channel safety mats without an additional safety CPU slot.
Controller compatibility and fieldbus fit
This F-module integrates natively with S7-1500 and S7-1200 controllers, including ET 200pro and ET 200S CPUs. For S7-300/400 systems, it requires an F-CPU and STEP 7 V11 SP1 or higher with the Safety V11 option package. It does not support PROFIBUS, DeviceNet, EtherNet/IP, MODBUS, CAN, or AS-Interface — the only fieldbus is PROFINET. Mounts via a clip onto the ET 200pro base unit. Overall depth is 49 mm including the angled SIMATIC Ethernet connector, so factor that into the enclosure depth when laying out the IP20-rated rear section.
Rated for ambient operation from -20 °C to 60 °C. The rear side carries IP20 protection, meaning it is suitable for dry, enclosed control cabinets — not for washdown or outdoor deployment. CE marked; no RoHS/REACH or UL listing appears in the available documentation.