Liquid level control relay — what the sensitivity range means
The RM4LG01M is a liquid level control relay from Schneider Electric's Harmony Relay range, designed to detect conductive liquid levels via resistive probes. Its sensitivity scale of 5...100 kOhm sets the probe resistance threshold at which the relay changes state — a 5 kOhm setting triggers on low-resistance (highly conductive) liquids like salt water, while 100 kOhm suits demineralised water or weak solutions. The single C/O output contact switches loads up to 250 V AC, with a maximum switching voltage of 440 V AC. The electrode circuit is limited to 24 V AC and 1 mA — safe for probe immersion without electrolysis damage.
DIN-rail fit and panel integration
At 22.5 mm wide (0.9 in), the RM4LG01M occupies a single 9 mm pitch module on a DIN rail — 2.5 pitches total. Screw terminals accept up to 2 x 2.5 mm² flexible wire without cable end, or 2 x 1.5 mm² with ferrule. Tightening torque is 0.6...1.1 N·m. IP20 at the terminals, IP50 on the casing — suitable for enclosed panel use, not washdown. Pollution degree 3 and overvoltage category III per IEC 60664-1 mean it handles industrial environments with conductive contamination and transient overvoltages up to 4 kV.