Speed monitoring relay with IO-Link
The Siemens 3UG5851-1AA40 is a digital monitoring relay purpose-built for speed supervision on rotating machinery — conveyors, fans, pumps, and spindle drives — where detecting an overshoot or undershoot condition is critical to process integrity or equipment protection. It covers a detection range from 0.1 to 6000 r/min, which means it handles everything from slow-turning agitators to high-speed spindles in a single device, without needing a separate pickup sensor. The relay integrates IO-Link communication, so the speed setpoints, trip delays, and actual speed values can be read or written over the IO-Link master, eliminating manual potentiometer adjustments on the panel door.
Key ratings and what they mean for fit
The 0.1 to 6000 r/min range determines the pulse-train frequency the relay can evaluate from a proximity switch or encoder input.
Integration notes
Supply voltage is 24 V DC — standard for control panels. The screw terminals accept 0.2–2.5 mm² conductors; strip length 8 mm. The relay's ON delay and tripping delay are set via IO-Link or, if IO-Link is not used, through the front-panel rotary switches (the description confirms both methods). The two changeover contacts are rated for typical control loads; verify the contact rating against your specific load (e.g., a 24 V DC solenoid or a 230 V AC contactor coil) to ensure adequate service life. The 38 mm housing width fits standard DIN-rail spacing alongside other SIRIUS 3UG5 series monitors.