Factors in the design of a power transfer system for inductively coupled oceanographic sensors

An outline is given of the factors involved in the design of a system for powering oceanographic sensors inductively coupled to a long mooring cable, in particular where the total system power must be held to an absolute minimum. A calculation is made of the total power that is transmitted down the cable for given minimum power into the sensors, assuming a fixed impedance for the seawater return path. Designs for both split and solid core couplers are given. The split core coupler is the more difficult of the two to design, principally because the highly corrosive saltwater environment precludes the use of cut metal cores so that lower permeability ferrite cores must be used.