Siemens 3SK1, 24V dc Safety Relay, 0 Safety Contacts

This safety relay provides monitored protection for sensors and safety-related circuits in industrial control systems. Designed for use with single-channel or dual-channel sensor inputs, it supports automatic or monitored start routines, cross-circuit detection and start-up testing. The device suits installations requiring a Compact protective element with spring-loaded terminals and combined screw Snap-on mounting for secure panel fitting.

• SIL3 and PL e safety performance for high-demand systems
• 1.2 W maximum power loss reduces heat dissipation
• 4 000 m maximum sensor cable run for long-distance wiring
• 99% safe failure fraction enhances diagnostic coverage
• 600 s maximum internal diagnostics interval maintains periodic checks

• Suitable for monitoring light barriers and laser scanners
• Used with magnetically operated switch monitoring NC-NO or NC-NC
• Ideal for protective door monitoring in machine safety circuits
• Can be used with emergency-off circuits and 2-hand switches
• Used for opto-electronic protection device integration

It accepts either one 2-channel sensor or two 1-channel sensors with monitored start-up and floating/non-floating sensor options.

With automatic start the typical restart time is 60 MS and recovery after power failure is typically 6 500 MS.

It operates between -25 °C and +60 °C and functions at altitudes up to 4 000 m with 10 to 95% relative humidity.

It uses push-in spring-loaded terminals supporting solid conductors 0.5 to 1.5 mm² and stranded conductors 0.5 to 1.5 mm² with appropriate core-end processing.

The product is intended for Class A EMC environments and may cause interference in regular settings without mitigation.