Neptune Systems

OS-1 Optical Level Sensor V2

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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

More Information
UPC 019962172359
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Product Questions

Is this the sensor for the DDR?
Question by: Adrian Diaz on Feb 10, 2020, 10:38 AM
Hey there,

Yes they are the same optical eyes!

Take care
Answer by: Thomas Billington on Feb 12, 2020, 2:19 PM
Do these sensors work in the dark? Will my ATK work when we turn off the house lights at night?
Question by: Charles Smith on Dec 28, 2019, 11:51 PM
Hey there,
Yes, they do work in the dark.

Please let us know if you need anything further and take care!
Answer by: Matt Lucero on Dec 31, 2019, 12:19 PM
Can this be hooked into a DOS unit or will it only with with the FFM? Thanks!
Question by: James Barnhill on Nov 25, 2017, 6:00 PM
The optical sensors, such as those in the DDR, have a different type of plug for use with the DOS. The OS-1 sensors have a stereo jack type plug and will not work with the DOS unfortunately.

Hope this helps!
Answer by: Zack on Nov 25, 2017, 11:48 PM
Do you think this would to monitor the level in a skimmer cup, if attached to the lid.
Question by: Dave Emery on May 27, 2017, 4:14 AM
This can be used as a high water level sensor on your collection cup. You could drill a small hole in the lid and mount to the lid, or you could use the OS-M-1 and use the magnetic mount to position inside of the collection cup.

Happy reefing!
Answer by: Zack on Jun 5, 2017, 1:07 PM
I just received the sensor and I was wondering if it is fully submersible, i.e. can I use it as low level sensor in the sump by just attaching it to the pump inside the sump, without drilling a hole in the glass? This way it will be fully submersed under 10" of water most of the time?
Question by: Alex Varlakhanov on May 23, 2017, 1:07 AM
The OS-1 sensors are submersible.

Have a great day!
Answer by: Zack on May 25, 2017, 4:59 PM
You guys are saying that the OS-1 cannot be used to create a water tight seal in an ATO reservoir but the Neptune site says otherwise - can you confirm?

Here's is the Neptune link: https://forum.neptunesystems.com/showthread.php?18373-Optical-Sensor-(OS-1)-Info-amp-Usage
Question by: PAUL BLAZEBY on May 13, 2017, 7:01 PM
Thanks for bringing this to our attention! This information does appear to differ from the initial information we had, but Neptune is definitely the authority on their products, so it would appear that with the supplied silicone gasket they can be used in this way.

Happy reefing!
Answer by: Zack on May 16, 2017, 3:54 PM
Can these be cleaned and what would be the recommended method. Before I replace the ones in my ddr that got gunked up with a film from with a bad batch of calcium I'd like to know in case it ever happens again. Thanks!
Question by: Mike Niemann on May 7, 2017, 10:48 PM
Hey there,
These can easily be cleaned up with a short soak in a solution made from regular white vinegar or citric acid solution. Usually 30-40 minutes will get any deposits right off and then a quick rinse before re-installing!

Happy reefing!
Answer by: Zack on May 10, 2017, 2:20 PM
Will it only work with the FMM Module?
Question by: Wyatt Smith on Feb 24, 2017, 11:46 AM
Hey there,
The Optical Sensor currently does require the FMM module to communicate with the Apex system.

Have a great day!
Answer by: Zack on Feb 27, 2017, 2:41 PM
Do you know the size of the holes that it wil fit in. I'm trying to get a custom bracket made
Question by: Chris Brunelle on Feb 24, 2017, 11:04 AM
Hey there,
The probe body is .5", so an installation hole size slightly greater than this will be fine. A 5/8" bit should make a properly sized hole.

Have a great day!
Answer by: Zack on Feb 27, 2017, 2:31 PM
Follow up question - is there a way to extend the 10' cable if necessary?
Question by: Todd Davidson on Feb 24, 2017, 9:58 AM
Hey there,
While we don't currently have an option for extending the optical sensor cable, we do have Aquabus extension cables which would allow you to move the module closer to the source if needed.

Have a great day!
Answer by: Zack on Feb 27, 2017, 2:07 PM
How long is the wire on this sensor?
Question by: Todd Davidson on Feb 23, 2017, 10:15 PM
Hey There,
This sensor has a 10' cable. If you have any other questions, let us know!
Answer by: Jason Smith on Feb 24, 2017, 8:14 AM
Do these sensor comes with brackets or we need to make them .
Do you a picture of the bracket
Question by: Chris Brunelle on Feb 23, 2017, 4:05 AM
Hey Chris,
This sensor does not include a mount at this time. The sensors can be mounted into custom brackets or through a hole in a vessel. If you have any other questions, let us know! : )
Answer by: Jason Smith on Feb 23, 2017, 7:49 AM