{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3UG4851-1AA40","brand":"Siemens","brandSlug":"siemens","productSlug":"3UG4851-1AA40","canonicalUrl":"https://aoctrl.com/siemens/3UG4851-1AA40","factsUrl":"https://aoctrl.com/api/mcp/products/3UG4851-1AA40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3UG4851-1AA40 RPM monitoring relay with digital setting, 24 V AC/DC, 22.5 mm width, IP20/IP40.","salesMarkdown":"The Siemens 3UG4851-1AA40 is a SIRIUS RPM monitoring relay with digital setting — it watches a rotating shaft or motor via a sensor input and trips an output if the speed falls outside a programmed window or below a threshold. It runs on a 24 V AC/DC supply (rated 24... 24 V) and draws up to 4 VA at 24 V maximum, so it fits into a standard 24 V control circuit without a separate power module. The output relay is rated 1 A at 24 V, 0.2 A at 110/125 V, and 0.1 A at 230/250 V — these are the switching limits for the alarm or trip signal, not a motor-load contactor. ## Configurable response and reset behavior Start-up delay is adjustable from 0 to 999.9 s, which lets you suppress nuisance trips during motor acceleration or conveyor start sequences. The relay supports both automatic reset (auto-RESET = Yes) and external reset via a remote pushbutton or PLC contact, giving the commissioning engineer flexibility for attended vs. unattended restart. An error memory (Error Memory = Yes) latches the fault state so the last trip condition is retained even if the monitored speed returns to normal — useful for post-mortem diagnostics on a line-down event. The housing is 22.5 mm wide, 91 mm high, and 102 mm deep — a standard single-module DIN-rail footprint that snaps onto the rail (screw and snap-on mounting) and leaves zero clearance needed on any side (0 mm upwards, forwards, backwards, downwards, and at the side). Terminals are rated IP20 (finger-safe), the enclosure is IP40, and the unit operates from -25 to +60 °C with storage/transport down to -40 °C — fine for most control cabinets and unheated warehouses. Pollution degree 2 (normal industrial environment) and galvanic isolation between input and output mean you can share a 24 V supply with the PLC without worrying about ground loops corrupting the speed signal.","metaTitle":"Siemens 3UG4851-1AA40 SIRIUS RPM Monitoring Relay, 22.5 mm","metaDescription":"Siemens 3UG4851-1AA40 SIRIUS RPM monitoring relay with digital setting. 24 V supply, configurable start delay and error memory. IP20 terminals, IP40 enclosure. Active lifecycle.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"NRND","categoryPath":["Process / Temperature Controllers"],"specifications":{"Depth":"102 mm","Solid":"20 ... 14","Width":"22.5 mm","Height":"91 mm","Upwards":"0 mm","at 24 V":"1 A","Forwards":"0 mm","Stranded":"24 ... 16","at 110 V":"0.2 A","at 125 V":"0.2 A","at 230 V":"0.1 A","at 250 V":"0.1 A","Backwards":"0 mm","Downwards":"0 mm","auto-RESET":"Yes","At The Side":"0 mm","Rated Value":"24 ... 24 V","Error Memory":"Yes","Initial Value":"0.75","When Starting":"0 ... 999.9 s","During Storage":"-40 ... +80 °C","External Reset":"Yes","Of The Terminal":"IP20","at 24 V maximum":"4 VA","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","Fastening Method":"screw and snap-on mounting","Full-Scale Value":"1.25","Of The Enclosure":"IP40","Product Function":"RPM monitoring relay","Delayed Switching":"0","Mounting Position":"any","Galvanic Isolation":"Yes","Product Brand Name":"SIRIUS","Between The Outputs":"No","Degree Of Pollution":"2","Product Designation":"Speed monitoring relay with digital setting","at AWG cables solid":"2x (20 ... 14)","protection class IP":"IP20","at 230 V at 50/60 Hz":"3 A","at 250 V at 50/60 Hz":"3 A","Design Of The Display":"LCD","IO-Link transfer rate":"COM2 (38,4 kBaud)","Instantaneous Contact":"0","Standstill Monitoring":"No","at AWG cables stranded":"2x (20 ... 14)","Between Input And Output":"Yes","Relative Repeat Accuracy":"1 %","Rotation Speed Monitoring":"Yes","Accuracy Of Digital Display":"+/- 1 Digit","Relative Metering Precision":"10 %","Substance Prohibitance (Date)":"05/01/2012","Type Of Electrical Connection":"screw-type terminals","Design Of Input Feedback Input":"No","Adjustable Operating Delay Time":"0 ... 99.9 s","With Lower Or Upper Limit Violation":"0 ... 999.9 s","operational current at 17 V minimum":"5 mA","Surge Voltage Resistance Rated Value":"4 kV","With Degree Of Pollution 2 Rated Value":"300 V","protocol is supported IO-Link protocol":"Yes","due to burst according to IEC 61000-4-4":"2 kV","number of CO contacts delayed switching":"1","number of NC contacts delayed switching":"0","number of NO contacts delayed switching":"0","reference code according to IEC 81346-2":"K","Finely Stranded With Core End Processing":"0.5 ... 2.5 mm²","Suitability For Use Safety-Related Circuits":"No","Tightening Torque With Screw-Type Terminals":"0.8 ... 1.2 N·m","shock resistance according to IEC 60068-2-27":"sinusoidal half-wave 15g / 11 ms","Between The Voltage Supply And Other Circuits":"Yes","Type Of Voltage Of The Control Supply Voltage":"DC","operating frequency with 3RT2 contactor maximum":"5 000 1/h","vibration resistance according to IEC 60068-2-6":"1 ... 6 Hz: 15 mm, 6 ... 500 Hz: 2g","Adjustable Open/Closed-Circuit Current Principle":"Yes","ampacity of the semiconductor output in SIO mode":"200 mA","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","electrostatic discharge according to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Type Of Voltage Supply Via Input/Output Link Master":"Yes","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Thermal Current Of The Switching Element With Contacts Maximum":"5 A","continuous current of the DIAZED fuse link of the output relay":"4 A","Of The Address Range Of The Inputs With Cyclical Transfer Total":"4 byte","Of The Address Range Of The Outputs With Cyclical Transfer Total":"2 byte","point-to-point cycle time between master and IO-Link device minimum":"10 ms","Product Component Removable Terminal For Auxiliary And Control Circuit":"Yes"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3UG4851-1AA40/alternatives.json"},"ai":{"faq":[{"question":"What are the key ratings for the 3UG4851-1AA40?","answer":"It operates on 24 V AC/DC (24... 24 V), draws 4 VA max, and its output relay switches 1 A at 24 V, 0.2 A at 110/125 V, and 0.1 A at 230/250 V. Start delay is adjustable 0–999.9 s."},{"question":"What is the mounting footprint and clearance requirement?","answer":"The housing is 22.5 x 91 x 102 mm (W x H x D) and mounts on a DIN rail with screw and snap-on fastening. Zero clearance is needed on all sides (0 mm upwards, forwards, backwards, downwards, and at the side)."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3UG4851-1AA40","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/3UG4851-1AA40 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}}