The Omron 61F-INL AC110/220 4KM is a High/Low Level controller from the 61F series, designed to monitor and control liquid levels in tanks, reservoirs, or process vessels. It accepts a 110/220VAC supply and drives two SPDT relay outputs (2 Form C), each rated at 3A @ 200VAC. The headline spec here is the 4 km maximum distance between the controller and the remote sensor electrodes — that's the '4KM' suffix. For a level relay, 4 km means you can place the controller in a central panel and run the electrode wires out to a tank farm or remote sump without signal loss or false triggering. Sensitivity is adjustable from 0 to 0.7 kΩ, which lets you tune the detection threshold for different liquid conductivities — clean water, wastewater, conductive process fluids all have different resistance values between the probe tips.
Mounts on standard DIN rail — snaps onto the top hat profile in the panel, screw terminals for the electrode and power connections. Alarm High/Low contact indication is built in — the front-panel LEDs and relay states give you a quick visual on whether the level is above the high probe, below the low probe, or in the normal band. Useful for a panel walk-by check without opening the door.
The 61F series has been around for decades, and the INL variant with the 4 km range is a standard stocking item.