The Omron 61F-GP-N-AC120 is a High/Low Level controller from the 61F series, designed to detect and control liquid levels in tanks, sumps, or reservoirs. It operates on a 120VAC supply and uses a relay output (SPDT, 2 Form C) rated at 3A @ 250VAC to switch pumps, valves, or alarms. The sensitivity range of 0 to 4kOhm lets you set the detection threshold to match the conductivity of the liquid — useful for water, wastewater, or mild chemical solutions where the probe resistance varies.
The 0~4kOhm sensitivity covers most conductive liquids; you adjust it via the front-panel trimmer to avoid false triggers from foam or scale buildup. The SPDT relay gives you both normally-open and normally-closed contacts, so you can wire it for fill (pump down) or empty (pump up) logic without an external inverter. The 1km maximum distance between controller and sensor means the probe can sit at the far end of a large tank farm or remote well — the controller stays in the panel, the probe goes where the liquid is. Socketable mounting with an 11-pin octal base (standard for this class) makes replacement fast — pull the old unit, plug in the new one, no rewiring of the base.