Instruments lowerd down to the ocean bed are not easy to control. Besides underwater modems the main control option is still based on wire connections. Instruments mounted on a frame (e.g. tripods) are
connected to a distribution box and data and power are controlled via a submersible cable. This cable acts as a connection between the submerged frame and a floating buoy were the data can be send via radio modems.
A battery source inside the buoy is powering up the instrument at the submerged frame.
The weakest link of this system is the cable itself. Tides, wind and other events are pulling, pushing and twisting on the cable, and the cable will eventually break. The biggest stress on the cable is
the torgue generated by twisting against a fixed support. A decoupling piece is neccessary to reduce the torque and the risk of breaking the cable.
To minimize the risk of cable breakage ARGUS developed a novel DATA-POWER-SWIVEL (DPS) which resists a load of 4...15 tons. The rotary joint contains an optical data unit. The data transfer is 115.2
kb/s. The serial data in- and output can be configurated as RS 485, 422, 232. The cable can be as long as 1.300 m depending on the cable quality (twisted pair). Another interesting feature is the possibility
of powering up instruments or charging batteries mounted on a submerged frame. The swivel contain a DC/DC converter which transforms power through an air gap (water gap). Thus the swivel galvanically isolates the
floating system from the submerged one galvanically.