Down Wire Net Monitor system
To be able to communicate with our various pelagic nets via a single conductive towing cable we use a BAS in house purpose build “Down wire net monitor” system. This system allows tow way communication via a single conductive cable. It is used to retrieve information from various under water sensors like depth, temperature and light and allows us to send signals down to control our nets during a deployment. The systems consist of a deck unit with a standard PC with a widescreen monitor and a modem, connected to the PC via RS232 and to the main cable via a coax cable. At the other end the under water unit consists of a UW-housing rated to 1000m, holding the electronics and a back up battery. All sensors are then plug into the UW-unit via connectors. It can take 6 sensors and has two outputs to control for example release mechanisms of our different nets. The sensor it can take are: depth, conductivity (salinity), temperature, light intensity, flow (current) and an altimeter.
It has a LavView graphical user Interface which is split into 4 logical areas: the sensor display for all the sensor information, the main depth over time display which also displays the distance to the sea floor as well as any nets events like opening and closing of the nets. The next display is for the control of the nets, and the last one displays the information from the winch with wire out, tension on the wire and so on. By now we have 4 fully interchangeable units with sensors, which mean there is a high number of redundancy, which makes this system very reliable, as you can swap any deck unit, underwater unit and sensor within minutes, to bring ship down time to a minimum. To make it even more interchangeable, all underwater units and the sensors are mounted on the same “cross” holder, making the fault finding and swapping an easy process.