A self-contained oceanographic depth recorder for high speed towing

This paper describes an instrument for recording depth of oceanographic and other underwater towed gear. A pressure-rated, streamlined housing contains the pressure sensing element and recording mechanism. The housing is rated for depths as deep as 1,000 feet and towing speeds as high as 40 knots. Basically, the depth sensing element works on the principle of displacing a precision-made, spring-loaded piston. The piston is displaced an amount proportional to the water pressure. A self-contained battery-powered drive mechanism makes a permanent record of the towing operation depth history. In this paper, specific details are given for the principle of operation, design of the streamlined housing, design for a specific depth range, drag predictions, expected error, calibration techniques, and maintenance procedures.