The Siemens 3UG5842-2AA40 is a digital monitoring relay that tracks current, active current, voltage, power factor (cos-phi), and power — all through a single device with IO-Link communication. It handles supply voltages up to 690 V AC/DC and a measurement path up to 10 A, with a 24 V DC control supply. The ON-delay and tripping-delay are independently adjustable from 0.1 to 999.9 seconds, giving you fine control over nuisance trips versus real faults. Output is a single changeover contact, terminated via spring-loaded terminals — no screw torque to verify, just strip and push.
What the ratings mean for fit
The 690 V AC/DC rated supply means this relay can be wired directly into 400 V line-to-line panels without a step-down transformer — common in European and IEC distribution. The 10 A measurement path is the through-conductor rating; the relay itself draws only its 24 V DC control supply from a separate source. The spring-cage terminals accept 0.2–2.5 mm² solid or ferruled stranded, which matches standard control wiring practice. IO-Link gives you parameterization and diagnostics over a single M12 cable — no analog scaling or threshold pots to set at the panel.
Where it fits in the panel
The package dimensions are 127 x 111 x 38 mm — a compact footprint for a multi-parameter relay. It is part of the SIRIUS 3UG monitoring relay family, designed for DIN-rail mounting in control cabinets. The spring-loaded terminals reduce wiring time and eliminate the risk of loose connections from vibration. The IO-Link interface means the relay can be configured and monitored from a PLC or IO-Link master without opening the panel door — useful for remote or hard-to-access installations.