Voltage threshold relay with adjustable hysteresis
The RM4UA01B is a voltage measurement relay from the Harmony RM4U series, designed for overvoltage or undervoltage detection on single-phase AC lines. It trips the 1 C/O output contact when the measured voltage exceeds or falls below the set threshold, with a hysteresis adjustable from 5 to 30 % of the threshold setting. No built-in time delay means the relay responds immediately to a threshold violation — useful for fast fault isolation but requires the downstream logic to handle transient events if the application needs a debounce window.
22.5 mm DIN-rail footprint, 2.5 module pitch
The housing is 22.5 mm wide (0.9 in), occupying 2.5 DIN module pitches on the rail. Depth is 80 mm (3.1 in), height 78 mm (3.07 in) — fits standard control-panel enclosures without crowding adjacent devices. Screw terminals accept 2 x 1.5 mm² flexible with ferrule or 2 x 2.5 mm² flexible without ferrule. Tightening torque range is 0.6...1.1 N·m (5.3...9.7 lbf·in). IP20 at the terminals, IP50 on the casing.
Active production, sourced to order
Compliance documentation includes EN/IEC 60255-6 for measuring relays, low-voltage directive 73/23/EEC, and EMC directive 89/336/EEC. Pollution degree 3 per IEC 60664-1, dielectric test voltage 2.5 kV.