What this level controller does on the line
The Omron 61F-G3NL AC110/220 4KM is a high/low level controller from the 61F series, built for liquid level detection in tanks, sumps, and process vessels. It runs on 110/220VAC supply and drives up to three relay outputs — two SPDT Form C contacts rated 3A at 200VAC — so you get independent alarm and pump control circuits from one unit. The headline spec is the 4 km maximum distance between the controller and the remote sensor electrodes. That means the controller can sit in a central panel while the probe heads are out at the tank farm or remote pit — no need to pull the controller out to the wet area. Sensitivity is adjustable from 0 to 0.7 kOhm, which covers most conductive liquids (water, mild chemicals, coolant) but lets you dial out false trips from foam or scaling. The alarm high contact output gives a dry-contact signal when the high-level setpoint is reached — useful for tying into a PLC input or a local beacon.
The three relay outputs are independent — you can wire one for pump-down control, one for high-level alarm, and one for low-level alarm or a remote indicator. Each SPDT contact gives you both NO and NC, so fail-safe logic (pump off on power loss) is straightforward.