What it is and what it does
The Omron 61F-G AC100/200 is a conductive-type liquid level controller from the 61F series, configured for High/Low Level detection — meaning it maintains a fill level between two probe points, not just a single overflow alarm. It accepts a dual-range supply of 100 or 200 VAC, so the same unit works on either a 100 V or 200 V line without rewiring. The sensing circuit triggers when the liquid resistance between probes falls within the adjustable 0 to 4 kOhm range. That covers most conductive liquids — water, weak acids, coolants — but not deionized water or hydrocarbons. The SPDT relay output (2 Form C) switches 5 A at 220 VAC, enough to drive a contactor or small pump directly.
Deployment context
The 61F-G AC100/200 mounts to a chassis or panel backplate via its integral mounting holes. Screw terminals accept field wiring directly — no socket required. The control-to-sensor distance can run up to 1 km from the controller to the probe electrodes, which suits tank farms or remote sumps where the controller sits in the MCC room and the probes are at the vessel. Operating temperature spans -10°C to 55°C, so it's fine inside a non-condensing enclosure but not for direct outdoor exposure or freeze-thaw environments.