Neptune Systems

OS-1-M Optical Level Sensor V2 With Mount

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$37.95 $37.95

Discontinued by Bulk Reef Supply
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Optical sensors are the go-to sensor if you want a reliability over a long period of time. The Neptune Optical Sensor plugs directly into the FMM allowing you to monitor the level of your sump, mixing station, or any other reservoir that has up to 1/4" thick walls.


Includes Magnetic Mount


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 on any type of reservoir that has up to 1/4" thick walls. 

  • Compatible with Neptune FMM Module
  • Magnet mounts to walls up to 1/4" thick
  • Can be mounted vertical or horizontal


What's Included?

1x OS-1 V2 Optical Sensor with nut and washer

1x OS-M Optical Sensor Magnetic Mount


Note: FMM Module required for use.

More Information
UPC 019962170454
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Product Questions

Do they offer an extension for the wire I need 15 feet minimum
Question by: Martin Germishuys on Sep 7, 2018, 9:09 AM
Hey there!

Unfortunately there is not any extension for these sensors.

Take care!
Answer by: Thomas on Sep 7, 2018, 2:16 PM
Hello I’m asking to see how long the wire for this is? Can’t find it anywhere.

Question by: Martin Germishuys on Sep 6, 2018, 8:45 PM
Hey there!

It is just a couple inches under 10 feet!
Answer by: Thomas Billington on Sep 7, 2018, 2:23 PM
Can this be used always submerged, as a low level alarm from the bottom of a reservoir? (Wet=no alarm dry=alarm)
Question by: Damion on Nov 24, 2017, 7:47 AM
They can be used in a reverse function. You will need to program it into your Apex but it is a simple open/closed statement.
Answer by: Charlie on Nov 24, 2017, 8:15 AM
Can you add this to a breakout box?
Question by: Stephen Jay on May 25, 2017, 8:03 AM
Hi Stephen,
The Optical Level Sensors require the FMM to operate. It is not compatible with the I/O Breakout Box.
Answer by: Charlie on May 26, 2017, 3:12 PM
I have several of these sensors without the mount... Can I buy just the mount?
Question by: Robert on May 24, 2017, 9:50 PM
Hi there,
Unfortunately at this time the mount is not sold separately.
Answer by: Charlie on May 26, 2017, 3:15 PM
Is the description correct, they can only be used on material up to 1/4" thick? That seems crazy thin. My sump is made of 3/8" material and using it directly on a glass tank would almost always be out of the question.
Question by: Clint on May 24, 2017, 6:41 AM
That is correct according to Neptune. Due to the very compact size of the magnets, I don't think Neptune is comfortable suggesting reliable use over this thickness and keeping the probes securely in place.

Happy reefing!
Answer by: Zack on May 30, 2017, 4:05 PM
Can you buy the FMM mode and water level sensors if you aren't in need to install in line flow motoring?

Can the solenoid be rigged to also shut off a water line as an emergency measure if the float valve fails?

Can these sensors be installed easily in 2 part resovoirs that arent from neptune?

How many can you comnect to an FMM?

Does it work with apex classic?
Question by: Allen Frady on May 23, 2017, 11:42 PM
The FMM module has 4 sensor ports which can be used for a variety of applications such as water level sensors, flow monitors, and leak detection. The solenoid can be plugged into the accessory port on the module as long as you have a power supply and can then be used to control flow as well. The solenoid is a normally closed solenoid, so will only open when power is applied. This could be used as a redundancy to the optical sensors as a mechanical means of stopping flow, but would only activate according to your programming for the sensor inputs.

Hope this helps!
Answer by: Zack on May 30, 2017, 3:31 PM
What is the cable length on this?
Question by: Michael Barcomb on May 23, 2017, 11:37 PM
The os-1 sensor has a cable length just under 10ft.

Happy reefing!
Answer by: Zack on May 30, 2017, 3:29 PM