NexSens CB-1250 User Guide

The NexSens CB-1250 Data Buoy is designed for deployment in lakes, rivers, coastal waters, harbors, estuaries and other freshwater or marine environments where environmental data collection is planned.


CB-1250 Data Buoy


Instrument Cage


Instrument Cage for CB-1250


Instrument Cage Assembly

  1. Place the cage security bracket onto the ends of the cage and frame.
    1. Reference the CB-1250 diagram below

      Cage Security Bracket



      CB-1250 Diagram



  2. Run the bolt with pinhole downward through the buoy frame. Place a lock washer and the castle nut onto the bolt. Use a pair of 1-1/8” or adjustable wrenches to tighten the castle nut.

    Bolt installation



  3. Place the end plates over the center bolt and secure with the three remaining bolts, lock washers and nuts. Tighten each securely.

    End plate installation



  4. Run the cotter pin through the hole in the center bolt and bend the long leg around one of the ridges on the castle nut.

Cotter pin installation


Solar Tower Testing 

Three 57W panels allow for solar charging when the buoy is facing any direction. As a precaution, these panels are diode protected in the instance that they are not receiving direct sunlight. When configured with factory installed batteries, a solar regulator is included in the data well. Otherwise, a solar regulator is required from an outside source.

Solar panel voltage output between pin 1 and pin 3 of the UW-6 SOLAR plug will oscillate between 8-20V depending on the available sunlight.

Connect the leads of a DC voltmeter to pin 1 and pin 3 to confirm the panels are producing the proper voltage.

UW-6 Plug pin connections



Safety First

Always follow safe marine and boating practices.


  • Heavy gear and boat clutter during deployment is unsafe. Care must be taken during deployment to maintain a clean and safe environment.
  • Use proper protective equipment (work boat, lifting rig, gloves, safety footwear, etc.) when deploying any buoy system.
  • Buoy systems are heavy, and personnel can quickly become entangled within mooring lines. Flotation gear should be worn at all times when working on or near the water.
  • Never deploy buoys in unsafe weather conditions.

Ballast Weight and Stability

To prevent overturning and ensure stability, additional ballast weight may be needed.


  • As configured at the factory, the buoy’s center of gravity is near the water surface. Any weight added above the water surface must be appropriately counterbalanced by additional ballast weight below the surface.
  • Be sure to keep topside devices lightweight and positioned as low as possible on the tower. Mount the ballast weight as low as possible on the underside of the buoy. It is preferred that the ballast weight be connected to the eye of the instrument cage.
  • It is recommended to use at least 200 lbs. of galvanized chain for ballast, however, the exact weight is dependent upon the conditions at the deployment location.
  • Before final deployment, some experimentation with ballast weight may be required to properly balance the buoy.

CB-1250 Ballast Weight Diagram



Mooring Options

Single-Point mooring diagram


Single-Point Mooring

When to Use

  1. In calm waters
  2. When monitoring sensors are attached to the instrument cage or housed in 914-M deployment pipes located within the three buoy pass-through ports.
    1. Secure sensor mounting prevents damage from debris and limits the entanglement from mooring lines.


  1. Attach a stainless steel mooring line to the bottom eye of the instrument cage.
    1. Ensure that the mooring line has adequate length to remain taut in the water column.
  2. Shackle a heavy chain to the bottom of the mooring line.
    1. Confirm that the chain is long enough so that the anchor cannot be lifted during high water conditions.
  3. Connect an anchor to the bottom of the chain.


Two-Point mooring diagram

Two-Point Mooring

When to Use

  1. When monitoring sensors or sensor strings are deployed in the water column directly below the buoy.
    1. This setup allows the mooring lines to be pulled taut away from the buoy, freeing the water column for a suspended sensor line.


  1. Attach short mooring lines to opposite eye nuts located on the bottom of the buoy frame.
  2. Secure each surface line and a water column line to a marker buoy.
    1. Ensure that the water column line has adequate length to remain taut in the water column.
  3. Shackle heavy chains to the bottom of each water column line.
    1. Confirm that the chain is long enough so that the anchor cannot be lifted during high water conditions.
  4. Connect an anchor to the bottom of each chain.



Important: This section contains only general information on the available mooring options for CB-1250 data buoys. To develop an effective mooring strategy, a variety of application-specific criteria (water level fluctuations, currents and wave action, debris loads, etc.) must be thoroughly reviewed prior to deployment. NexSens does not endorse any particular mooring strategy for any specific application.