What it is and what it does
The Omron 61F-GNL AC110/220 4KM is a conductive-type level controller from the 61F series, designed for high/low level detection in tanks or reservoirs. It operates by sensing conductivity through electrodes in the liquid — when the resistance between probes drops below the set threshold (0 to 0.7 kOhm adjustable), the internal SPDT relay switches. That relay contact is rated 3A at 200VAC, enough to drive a small pump contactor or alarm. The headline spec here is the 4 km maximum distance between the controller and the sensing electrodes — that's not a typo. It means the controller can sit in a central panel while the probes are at the far end of a long tank farm or remote sump, without signal degradation. For comparison, many level relays top out at 100 m or 1 km.
Power and mounting
Powered by 110 or 220 VAC — selectable, not auto-ranging — so verify your line voltage before wiring. The screw terminals accept standard panel wire, and the housing snaps onto a DIN rail. Operating range is -10°C to 55°C, which covers most indoor control rooms and sheltered outdoor enclosures.