What this relay does on the line
The RM4JA01M is a current measurement relay from the Harmony RM4J family, designed to monitor AC or DC current and trip its output when the measured current exceeds the set threshold. It covers three switchable ranges: 0.3...30 mA, 10...100 mA, and 100...1000 mA, for both AC (50/60 Hz) and DC — so one relay handles low-level leakage, intermediate loop currents, and higher motor-phase draws without swapping modules. The single changeover contact (1 C/O) switches up to 250 V AC, with a maximum switching voltage of 440 V AC — enough to drive a PLC input or a small contactor coil directly.
Panel fit and environmental rating
The relay occupies a 23 mm wide DIN-rail footprint (0.9 in), 80 mm deep, 78 mm tall — fits standard 35 mm rail alongside contactors and terminal blocks. IP20 at the terminals, IP50 on the casing — protected against dust ingress and finger-safe, but not rated for washdown; keep it inside a sealed enclosure if the panel sees hose spray or condensation. Rated for pollution degree 3 per IEC 60664-1, meaning it tolerates conductive dust and occasional condensation typical in industrial control cabinets.
Lifecycle and sourcing reality
It is designed and tested to EN/IEC 60255-6 (measuring relays and protection equipment), with dielectric test voltage of 2.5 kV and immunity to fast transients at 2 kV level 3 per IEC 61000-4-4.