Neptune Systems Optical Sensor Optical sensors are the go to sensor if you want a reliable sensor over a long period. The Neptune Optical Sensor plugs directly into the FMM allowing you to monitor the level of your sump, mixing station, or any other reservoir with liquid in it. This sensor plugs into your FMM and, using reflected infrared light, will signal your Apex when it changes state from being wet to dry or dry to wet. This sensor can be used for constructing your own ATO (auto-top-off), as a high-level warning sensor in your sump, water storage level sensor, and much more. The sensors can be mounted into custom brackets or through a hole in a vessel. Included are a fastening nut and silicone washer. What's Included? 1x OS-1 V2 Optical Sensor with nut and washer
