Inductive Modem

RBR’s inductive modem communication system, the MLM-1000 is designed to provide fast communication with deployed instruments. It is available as an option on any of our standard instruments, or as a standalone variant to which any device with a serial line may be attached. The modem uses an underwater transformer to transmit information through a jacketed mooring line without requiring cables or connectors. Instruments may be connected to the MLM-1000 and communication at 4800 baud is provided over a jacketed mooring line. Features include transparent link, automatic node discovery, and CRC error detection.

The MLM-1000’s head-end modem can act as a simple system controller by autonomously polling each instrument at regular intervals. Each polled data packet can be transmitted via a directly-connected RF, cellular, or satellite telemetry. The conductor loop is comprised of the steel core of a jacketed mooring cable and sea or fresh water. The ends of the steel cable are stripped of the insulating jacket and are thus in contact with the water. Between the stripped ends of the cable, the water provides a conduction path for electric current. Each system node typically uses a toroidal transformer that is clamped around the mooring line. The magnetic coupling between the toroid and the mooring cable is the medium by which information is transferred between the mooring cable and the particular system node.

Main Features

  • The ability to receive oceanographic measurement data from any one of a network of deployed RBR logger instruments in soft real time.
  • The ability to alter sampling regimes for already deployed logger instruments, for example in response to changing marine environmental conditions.
  • The ability to gauge the status and functional health of deployed instruments.
  • The ability to download data from logger instrument memory while the instrument is deployed.

MLM-1000 inductive modem datasheet