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Session 1559

An Innovative Student Project to Develop a Precision Instrument for Undersea pH Measurements

Stuart Wilkinson, Ph.D., G. Mark Pennington, M.S.M.E. University of South Florida

Abstract

The present paper describes the design and prototype construction of a teleoperated robotic sensor for precision pH measurement of sea water at deep ocean locations. The need for such an automated device originated with NOAA. The design and construction was undertaken at the USF Mechanical Engineering Department's Robotic Systems Laboratory. The completed prototype will be utilized for research purposes by the USF Marine Science Center in St. Petersburg.

Introduction

The design work centered around the automation and miniaturization of an existing laboratory procedure to facilitate remote undersea precision pH measurement (to 1/1000th of a pH unit). The laboratory procedure known as spectrophotometric testing [1] involves 6 basic steps:

1. sample the sea water or fill - collect sample at the appropriate depth. 2. base-line test - spectrophotometrically analyze a controlled light source passing through the sample. 3. indicator-dye injection - injecting a metered amount of indicator-dye into the sample. 4. indicator-dye mix - mixing the dye into the sample. 5. dye-reacted test - spectrophotometrically analyze a controlled light source passing through the sample. 6. test chamber flush - thoroughly eject current sample to allow recycle to next sample.

The layout of the device involved subdividing the 6 basic steps into three groups, each containing 2 steps; namely: fill/flush, base-line test/dye-reacted test, and dye injection/dye mix. The 3 groups were accommodated with a revolving cylindrical core placed within an outer casing. The core contained a test chamber which served as a container for the sample and would revolve on a central shaft supported by bearings. Each of the 3 groups of operational steps were given a station position, such that the test chamber was able to be indexed to each station in turn where the appropriate procedures could be performed.

Constraints & Material Selection

The constraints on the design fell into 2 major categories: material & operational. The material constraint is that neither the sea water sample or indicator dye could make any contact with metals as this would adversely affect the precision of the pH measurement. The operational constraints were that the device must maintain proper function in any physical orientation and the sample could not contain air pockets.

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Wilkinson, S., & Pennington, G. M. (1997, June), An Innovative Student Project To Develop A Precision Instrument For Undersea P H Measurements Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6620