Problem
Oregon State University College of Oceanography needed a device to gather multiple samples of plankton. The sampler was to be lowered from a ship on a cable to various depths and samples were to be collected on command.
Solution
The Plankton Sampler had a rotating "lazy susan" carriage with nine removable buckets containing fine mesh bags to collect the samples. A large pump forced sea water through a center column and plenum into a sample net. After a sample was completed the pump was stopped and the carriage was rotated to bring the next net bucket into position for another sample.
A major problem was the cable that suspended the sampler. It had a strong outer metal jacket that supported the sampler and three small diameter center conductors. Three phase AC motor power and bidirectional communications had to be carried in the conductors. Further, the conductors were too small to carry the current necessary to drive the pump. The solution was to provide three phase 2250VAC from the ship and step down transformers and power supplies in the sampler to produce voltages to power the motor and electronics. At the shipboard end and sampler end of the cable, data was injected onto the 2250VAC power and recovered with a proprietary three-channel FSK modem receiver.
The entire assembly was framed in a heavy steel cage to provide protection when handling alongside ship, and the electronics was packaged in an oil-filled pressure case to allow operation at great depths.
Results
The Plankton Sampler was deployed on several cruises and allowed detailed analysis of species content and population numbers of ocean plankton.