The Omron 61F-GN AC110/220 is a conductive-type level controller from the 61F series, designed for high/low level detection in tanks, reservoirs, and process vessels. It operates on a dual-voltage supply of 110/220VAC and switches a relay output based on the resistance between its probe electrodes.
The 0 ~ 4kOhm sensitivity range means the controller triggers the relay when the resistance between the common and level probes drops below the set threshold — typical for water-based conductive liquids (tap water, coolant, wastewater). For liquids with lower conductivity (deionized water, some oils), the 4kOhm upper limit may not detect reliably; a lower-sensitivity model would be needed. The SPDT (2 Form C) contact arrangement provides one normally-open and one normally-closed set of changeover contacts per pole, rated 3A at 200VAC. That's enough to drive a small pump contactor coil or a pilot light directly, but not a motor load — the relay contacts are for signal-level switching, not power. The 1 km maximum distance between the controller and the sensor head means the probe wiring can run across a large plant floor or between buildings without signal degradation, as long as the cable resistance stays within the 4kOhm sensitivity window.