The Omron 61F-GP-N8D AC120 is a High/Low Level controller from the 61F series, designed for tank fill and drain applications where two probe setpoints maintain liquid level between limits. It runs on a 120VAC supply and switches a SPDT (2 Form C) relay rated at 3A @ 250VAC — enough for direct control of a small pump contactor or solenoid valve.
The sensitivity range of 0 to 1.3 kOhm sets the probe resistance threshold at which the relay changes state. For conductive liquids (water, weak acids, coolants), use a lower probe resistance; for non-conductive or high-resistivity media, the upper end of the range accommodates longer probe runs or higher-impedance sensing. The 1 km maximum distance between controller and sensor means the probes can be placed at the far end of a large tank or remote sump without signal degradation. The SPDT relay output gives you both normally-open and normally-closed contacts, so you can wire for either fill-to-high-level (pump off at high) or drain-to-low-level (pump on at low) without adding an external logic relay. The 3A contact rating at 250VAC covers most pilot-duty loads; for larger pump motors, interpose a contactor.
This class of level controller is common in water and wastewater tanks, coolant sumps on machine tools, chemical holding vessels, and condensate return systems.