Guide to Inductive Moorings

Real-time ocean observing systems provide critical information for the study of ecosystems, water quality, and fisheries, as well as data for long-term climate change studies. Wireless (satellite/mobile) telemetry has made real-time, unattended, remote oceanography increasingly practical.

Traditional real-time moorings required failure-prone breakouts for direct cable connections to instruments. These systems also lack flexibility, because the location and type of each instrument is fixed once the cable is manufactured.

Sea-Bird’s Inductive Modem (IM) system provides reliable, real-time data transmission for up to 100 instruments that can be positioned or repositioned at any depth. The IM system supports both autonomously operating instruments and those that require a command to take a measurement and return the data. Global commands to take and store a measurement can be sent to all instruments on the mooring line. Data is retrieved by sending a command to each instrument, using its unique ID, to transmit its data.

Sea-Bird’s IM system transmits commands and data between an Inductive Modem Module (IMM) in the surface buoy and up to 100 IM-enabled instruments on a plastic-jacketed steel mooring line, without the need for breakouts

1. 1. Underwater Instruments – up to 100 IM-enabled instruments can be on the mooring cable, including:

      Instrument	Temperature?	Conductivity?	Pressure (optional)?	Other? / Notes
      SBE 16plus-IM V2	x	x	x	Up to 7 auxiliary sensors, such as dissolved oxygen, turbidity, fluorescence, PAR, etc.
      SBE 37-IM	x	x	x
      SBE 37-IMP	x	x	x
      SBE 37-IMP-ODO	x	x	x	Dissolved oxygen
      SBE 39plus-IM	x		x
      UIMM				Adapts RS-232 instruments (acoustic current meters, Doppler profilers, optical sensors, etc.) for IM moorings

   2. Inductive Modem Module (IMM) – small printed circuit board housed in buoy that communicates with IM instruments and interfaces to a computer/data logger via RS-232 serial connection. Commands to IM instruments can be global (for example, command all instruments to take and store a measurement now) or addressed to an individual instrument (for example, send your data now). Data can be received from only one instrument at a time.
      

      

   3. Inductive Cable Coupler (ICC) – couples mooring line to IMM via a waterproof bulkhead connector through the buoy hull. Clamps along the plastic-jacketed portion of mooring cable, below the seawater ground. For typical moorings; optional.
      

      

   4. Mooring cable* – plastic-jacketed steel mooring line, used as both the data transmission line and the mooring support line for the instruments. This type of rope is frequently also used for non-inductive oceanographic moorings because of the corrosion resistance provided by the plastic jacket. It is not necessary to provide any electrical connection between instrument and cable; expensive and unreliable electro-mechanical cables and terminations are not needed to get real-time data.
   5. Buoy controller* – housed in buoy and connected to IMM via RS-232. Programmed to send commands to IMM to poll each underwater IM instrument for data and send data to shore via mobile or satellite transmission.
   6. Surface buoy* - houses IMM, controller/data logger, telemetry transmitter/receiver, and power supply.
   7. Shore installation* – houses telemetry receiver (and optional transmitter, permitting shore control of buoy function) and computer for logging, processing, and displaying data.
   *Not supplied by Sea-Bird.