What it is and what it does
The Omron 61F-GP-NT AC120 is a High/Low Level controller from the 61F series, designed to detect and control liquid levels via electrode probes. It operates on a 120VAC supply and switches a SPDT relay (2 Form C) rated at 3A at 250VAC. The sensitivity range of 0 to 4kOhm covers most conductive liquids — water, weak acids, coolants — where the resistance between probes drops below the set threshold.
Key ratings and what they mean for fit
The 0 to 4kOhm sensitivity range is the core selection parameter. Set it to the actual resistance of your liquid at operating temperature — clean water is roughly 10-50 kOhm per cm, so this controller works with a probe spacing that keeps the loop resistance under 4 kOhm. The 600m maximum distance between controller and sensor means the electrode head can be placed far from the panel, useful for deep tanks or remote sumps. The SPDT relay output (2 Form C) at 3A/250VAC drives a small pump contactor or alarm directly. If your load exceeds 3A, interpose a power relay. The socketable octal base (8-pin plug-in) makes replacement a 30-second swap — no rewiring, which matters when a sump pump controller fails at 2 AM.
Where it goes in the panel
The 61F-GP-NT AC120 mounts via its octal socket to a DIN rail or panel. The 8-pin plug-in termination matches standard relay sockets (e.g. Omron PYF-08A or equivalent). Keep the controller within the -10°C to 55°C operating range — that covers most indoor panel environments but not direct sun or steam-valve proximity.