The Omron 61F-G3N AC100/200 is a conductive liquid level controller from the 61F series, designed for high/low level detection in tanks, sumps, and process vessels. It operates on a 100/200VAC supply and provides three relay outputs (SPDT, 2 Form C) rated at 3A @ 200VAC. The sensitivity is adjustable from 0 to 4kΩ, which lets it work with different liquid conductivities — from clean water to mildly conductive process fluids. The control-to-sensor distance can run up to 1 km, so the controller can sit in a central panel while the electrodes are out on the tank.
The 0 ~ 4kΩ sensitivity range is the critical spec for the application engineer: it determines whether the controller can detect the liquid level reliably. Low-resistance liquids (tap water, many coolants) are easy; high-resistance liquids (deionized water, some chemicals) may need the sensitivity turned up or a different probe. The 1 km maximum distance between controller and sensor means the 61F-G3N can drive long cable runs without false triggering — useful for large tank farms or remote sumps. The SPDT (2 Form C) relay outputs give you one normally-open and one normally-closed contact per relay, which is enough to drive a fill valve and a high-level alarm, or a pump and a low-level alarm, without adding interposing relays. The 3A @ 200VAC contact rating handles small contactors and pilot lights directly; for larger loads, use the relay to switch a contactor coil.
Wire the supply and electrodes to the screw terminals and set the sensitivity pot.