Neptune Systems Magnetic Optical Sensor

The MOS (Magnetic Optical Sensor) by Neptune Systems is a refined upgrade over the original OS-1-M, designed for enhanced reliability and a more compact form factor. This sensor provides precise water level detection using infrared optical technology and connects directly to any Apex FMM port.

With its built-in magnetic mount, fully waterproof body, and slimline design, the MOS is ideal for use in tight spaces such as sumps, dosing containers, or ATO reservoirs.

Key Features

• Improved design for durability and performance

• Accurate wet/dry detection using infrared light

• Fully waterproof sensor body

• Strong magnetic mount—compatible with glass or acrylic up to 12 mm thick (½”)

• Silicone-encased external magnet to prevent slipping or corrosion

• Compact size—fits easily in cramped or narrow compartments

• Plugs directly into Neptune FMM ports

Versatile Applications

The MOS sensor is suitable for a wide range of water-level automation and safety functions:

• Auto Top Off (ATO) systems

• High/low sump level alerts

• RO/DI water storage monitoring

• Leak prevention automation

• Dosing reservoir tracking

The sensor communicates wet/dry status to your Apex Controller via the FMM module, triggering alarms, automation routines, or equipment shutdowns as needed.

Compatibility

• Works with all Neptune FMM Modules (Standalone or integrated)

• Suitable for use on reservoirs or chambers with wall thicknesses up to 6 mm (¼”) for internal mounting, and up to 12 mm (½”) with the external magnet

• Requires an Apex Controller with available FMM port

What’s Included

• 1x MOS Magnetic Optical Sensor

• Built-in magnetic mounting system

  Note: Requires Neptune Apex Controller and FMM module (standalone or embedded) for operation. Sensor cable is pre-attached.