Oceanographic CTD sensor
A university Group Design Project to develop and design a combined Conductivity, Temperature and Depth (CTD) sensor for implementation on the 'ecoSUB µ5', for operation at depths of up to 500m in waters such as the North Sea.
From our initial brief, and consideration of our target market / stakeholders, we determined high-level project aims and specific objectives, which informed the generation of a list of technical design requirements. As a team, we worked to specify the sensors & required electronics for the instrument. For the mechanical design of the unit, we used a weighted-parameter approach (a binary weighting matrix), based on the product design requirements. This was used to evaluate concepts and make high-level team design decisions. My primary role was to then translate this high-level specification into a concrete product design that was suitable for manufacture.
Mechanical Design Overview
(Expand for detailed info)
To ensure physical compatibility with the ecoSUB μ5, the nose cone and its internal components were designed around the existing geometry present in the ecoSUB. A priority when locating components was to maximise the remaining volume within the cone, so that the end user may install additional, custom payloads of their own, greatly increasing the flexibility of the product.
The interior of the nosecone will be flooded (courtesy of peripheral flooding holes), so the cone itself need not function as a pressure vessel; this greatly reduces the risk of the cone buckling and removes restrictions on geometry (enabling components to pierce the outer wall). The water-tight pressure housing for the electronics consists of a permanent resin enclosure for all but the conductivity sensor, which is held directly by the nose cone. The other two sensors are contained within the resin, and their sensing interfaces exposed to the external water through two streamlined portholes in the side of the hull, which are designed to ‘scoop’ water over the sensors whilst minimising drag.
The assembly consists of three major components: the resin-encased electronics (including pressure and temperature sensors), the conductivity probe, and the nose cone itself. Assembly and disassembly are straightforward, with the first two sliding easily into the latter (whilst the sensors are exposed, they are flush so that they do not interfere with assembly).
Sensors were carefully placed so that they did not alter the exterior, circular profile of the ecoSUB when viewed end-on. This provides two direct benefits: reduced hydrodynamic drag and retainment of the ecoSUB’s capability to be deployed with a launch-tube. With the resin coating all components and the isolation of the temperature sensor from the sea water due to the waterproofing necessity, it was decided that a heat pipe should be used to bridge the temperature sensor to the environment so that it could measure temperature.
Engineering Drawings to BS8888
This assignment was graded 1st class and was subsequently selected by the University to be showcased to the ecoSUB team.