The Omron 61F-G4NR AC110/220 is a High/Low Level controller from the 61F series, designed to monitor and control liquid levels using conductive probes. It accepts a dual-range supply of 110/220VAC, making it straightforward to wire into existing panel voltage without a separate transformer. Sensitivity is adjustable from 0 to 1.1 kOhm, which covers most conductive liquids — water, weak acids, coolants — and the relay output (six relays total, configured as SPDT 2 Form C and 3 Form C) switches up to 3A at 200VAC. That contact rating is enough to drive a small pump contactor or alarm annunciator directly. The distance from controller to sensor can run up to 800 meters, which covers long tank runs in a plant.
The 0~1.1 kOhm sensitivity range means the unit detects liquid presence based on the resistance between probes. For clean water (typically 1–10 kOhm), you set the threshold near the low end; for more conductive fluids like brine or coolant, you adjust upward. This is the parameter that decides whether the controller triggers on foam, residue, or actual liquid — so dial it in during commissioning. The 800-meter maximum distance between controller and sensor is a practical spec for large tanks or remote sumps. It means the sensing head can be placed far from the panel without signal degradation, as long as the probe wiring stays within that loop resistance.
This class of level controller is common in water treatment, chemical dosing, coolant sump monitoring, and packaging machinery where a tank needs high/low level alarms or pump control. The idling prevention feature (listed in the specs) automatically stops the pump if the liquid level drops below the low probe, protecting the pump from running dry.