{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-2AB40","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-2AB40","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-2AB40","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-2AB40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-2AB40 safety relay, 24 V rated, SIL 3 (IEC 61508) / PL e (ISO 13849-1), 22.5 mm width, screw and snap-on mounting.","salesMarkdown":"Siemens 3SK1121-2AB40 is a SIRIUS safety relay for relay enabling circuits. It mounts on DIN rail (screw and snap-on, any position) and occupies 22.5 mm width with 121.6 mm depth. Rated at 24 V with a DC tolerance of 0.8 to 1.2 times nominal, it switches 1 A at 24 V, 1.5 A at 115 V, and 1.5 A at 230 V — enough to drive contactors or smaller motor starters in a safety circuit. The total current through the relay must stay under 12 A, and power loss tops out at 2 W, so no special ventilation is needed in a typical panel. This relay carries SIL 3 per IEC 61508 and IEC 62061, and PL e per ISO 13849-1. That's the highest performance level for a single-channel safety device under the current standards. It means the probability of dangerous failure per hour is below 10⁻⁷, and with a safe failure fraction of 99%, nearly every failure that occurs will be detected and force the safe state. For the buyer: this part is certified for Category 4 / PL e safety functions — the kind you need for light curtains, two-hand controls, or perimeter guarding where a single fault cannot lead to loss of safety. Response time is 30 ms typical, 50 ms maximum — fast enough to stop a servo-driven axis before a hand reaches the pinch point in most applications. The sensor input minimum pulse is 75 ms, so it filters out contact bounce from mechanical safety switches without extra external timers. ## Terminal wiring and environment Terminals accept solid wire from 20 AWG to 16 AWG (1x or 2x) and stranded wire in the same range. If you're using ferruled ends, the acceptable range narrows to 0.5 to 1.0 mm². Shock resistance is 10 g for 11 ms — enough to survive a forklift bump against the panel but not a direct hammer blow. The EMC emission standard is IEC 60947-5-1 Class A, so it's suitable for industrial environments without additional filtering.","metaTitle":"Siemens 3SK1121-2AB40 SIRIUS Safety Relay, SIL 3 / PL e, 22.","metaDescription":"Siemens 3SK1121-2AB40 SIRIUS safety relay. SIL 3 (IEC 61508), PL e (ISO 13849-1). 24 V rated, 1.5 A at 230 V. 22.5 mm wide, screw/snap-on mount. Current production. Quoted to order","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Safety Relays"],"specifications":{"Depth":"121.6 mm","Solid":"1x (20 ... 16), 2x (20 ... 16)","Width":"22.5 mm","at DC":"0.8 ... 1.2","Height":"100 mm","Maximum":"50 ms","Typical":"30 ms","at 24 V":"1 A","Stranded":"1x (20 ... 16), 2x (20 ... 16)","at 115 V":"1.5 A","at 230 V":"1.5 A","Rated Value":"24 V","Start Input":"Yes","Safety Switch":"Yes","at DC maximum":"110 ms","During Storage":"-40 ... +80 °C","Feedback Input":"Yes","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting","Product Category":"Safety relays","Shock Resistance":"10g / 11 ms","Mounting Position":"any","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"safety relays","Overvoltage Category":"3","Design Of The Product":"Relay enabling circuits","Total Current Maximum":"12 A","according to IEC 61508":"3","according to IEC 62061":"3","power loss [W] maximum":"2 W","Design Of The Cascading":"yes","Safety-Related Circuits":"Yes","EMC emitted interference":"IEC 60947-5-1, Class A","With Core End Processing":"1x (0.5 ... 1.0 mm²), 2x (0.5 ... 1.0 mm²)","according to ISO 13849-1":"e","Of The Sensor Input Minimum":"75 ms","Operating Frequency Maximum":"360 1/h","Safe failure fraction (SFF)":"99 %","Without Core End Processing":"1x (0.5 ... 1.5 mm²), 2x (0.5 ... 1.5 mm²)","Type Of Electrical Connection":"spring-loaded terminal (push-in)","Insulation Voltage Rated Value":"300 V","Monitoring Of Floating Sensors":"Yes","Product Function Parameterizable":"sensor floating / sensor non-floating, monitored start-up / automatic start, 1-channel / 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, 2-hand switches","Safety-Related Delayed Switching":"0","Monitoring Of Non-Floating Sensors":"Yes","Relative Humidity During Operation":"10 ... 95 %","air pressure according to SN 31205":"90 ... 106 kPa","of the ON pushbutton input minimum":"0.15 s","Product Feature Cross-Circuit-Proof":"Yes","operational current at 17 V minimum":"5 mA","Cascading Input/Functional Switching":"Yes","Safety-Related Instantaneous Contact":"3","Surge Voltage Resistance Rated Value":"4 000 V","category according to EN ISO 13849-1":"4","protection class IP of the enclosure":"IP20","stop category according to EN 60204-1":"0","installation environment regarding EMC":"This product is suitable for Class A environments only. In household environments, this device can cause unwanted radio interference. The user is required to implement appropriate measures in this case.","Magnetically Operated Switch Monitoring":"Yes","reference code according to IEC 81346-2":"F","Recovery Time After Power Failure Typical":"6.5 s","Suitability For Interaction Press Control":"Yes","Touch Protection Against Electrical Shock":"finger-safe","safety device type according to IEC 61508-2":"Type B","For Signaling Function Instantaneous Contact":"1","Type Of Electrical Connection Plug-In Socket":"No","Type Of Voltage Of The Control Supply Voltage":"DC","Number Of Sensor Inputs 1-Channel Or 2-Channel":"1","Required Spacing For Grounded Parts At The Side":"5 mm","Type Of The Safety-Related Wiring Of The Inputs":"single-channel and two-channel","hardware fault tolerance according to IEC 61508":"1","vibration resistance according to IEC 60068-2-6":"5 ... 500 Hz: 0.75 mm","PFHD with high demand rate according to EN 62061":"2.5E-9 1/h","suitability for operation device connector 3ZY12":"Yes","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","PFDavg with low demand rate according to IEC 61508":"7E-6","Installation Altitude At Height Above Sea Level Maximum":"4 000 m; Derating, see Product Notification 109792701","Recovery Time After Opening Of The Safety Circuits Typical":"30 ms","Thermal Current Of The Switching Element With Contacts Maximum":"5 A","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms","design of the fuse link for short circuit protection of the NC contacts of the relay outputs required":"Diazed or Neozed fuses, operating class gL/gG: 6 A or MCB type A: 2 A or MCB type B: 2 A or MCB type C: 1 A","design of the fuse link for short-circuit protection of the NO contacts of the relay outputs required":"gL/gG: 6A or circuit breaker type A: 3A or circuit breaker type B: 2A or circuit breaker type C: 1A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3SK1121-2AB40/alternatives.json"},"ai":{"faq":[{"question":"What is the width and mounting of 3SK1121-2AB40?","answer":"Width is 22.5 mm. Mounting is screw and snap-on onto DIN rail, in any position. Depth is 121.6 mm, height is 100 mm."},{"question":"What wire sizes does this safety relay accept?","answer":"Solid wire: 1x or 2x from 20 AWG to 16 AWG. Stranded wire: same range. With ferruled ends: 0.5 to 1.0 mm²."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-2AB40","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3SK1121-2AB40 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-09-02T08:15:54.622Z","lastPublished":"2026-09-02T08:15:54.622Z","indexable":true}}