A NEW APPROACH TO THE PROBLEM OF OBTAINING STABLE, LONG-TERM ELECTRICAL CONDUCTIVITY MEASUREMENTS IS INVESTIGATED, WITH EMPHASIS ON THE ACHIEVEMENT OF A CELL/ELECTRODE/ELECTRONICS DESIGN RESISTANT TO INTENSE BIOLOGICAL ACTIVITY, AND CAPABLE OF ACCURATE

A NEW APPROACH TO THE PROBLEM OF OBTAINING STABLE, LONG-TERM ELECTRICAL CONDUCTIVITY MEASUREMENTS IS INVESTIGATED, WITH EMPHASIS ON THE ACHIEVEMENT OF A CELL/ELECTRODE/ELECTRONICS DESIGN RESISTANT TO INTENSE BIOLOGICAL ACTIVITY, AND CAPABLE OF ACCURATE PERFORMANCE WHEN USED IN LONG-DURATION UNATTENDED APPLICATIONS ON MOORED SENSOR STRINGS. THE OBJECTIVE IS A SENSOR AND ASSOCIATED ELECTRONIC CIRCUITRY CAPABLE OF MAINTAINING AN ACCURACY WITHIN 0.010 MMHO/CM WHEN DEPLOYED FOR PERIODS OF UP TO ONE YEAR. A NOVEL CELL DESIGN IS HYPOTHESIZED WHICH IS EXPECTED TO BE ENTIRELY FREE OF PROXIMITY EFFECTS. PROTOTYPE CELLS, WITH INTERFACE ELECTRONICS OF SUITABLE CONFIGURATION, ARE FABRICATED AND SUBJECTED TO LABORATORY TESTS FOR ACCURACY AND STABILITY, PRIOR TO EXPOSURE TO CONDITIONS OF KNOWN INTENSE BIOLOGICAL ACTIVITY. THE CELLS ARE RETRIEVED AFTER SUITABLE INTERVALS AND TESTED FOR DRIFT. A SUCCESSFUL OUTCOME WILL PERMIT THE SUBSEQUENT DEVELOPMENT OF SENSORS SUITABLE FOR USE ON MOORED STRINGS PRESENTLY LIMITED TO MEASUREMENT OF TEMPERATURE AND WATER CURRENT. THESE STRINGS ARE IN ROUTINE USE, BUT ARE LIMITED IN VALUE BECAUSE OF THEIR INABILITY TO PROVIDE TIME-SERIES DATA RELATING TO SALINITY, DENSITY, SOUND VELOCITY, AND OTHER PARAMETERS. THE EXISTENCE OF SUITABLE SENSORS FOR ELECTRICAL CONDUCTIVITY WOULD ADD LITTLE TO THE COST OF THESE STRINGS WHILE CONTRIBUTING SUBSTANTIALLY TO THEIR SCIENTIFIC UTILITY. THE INCREASING EMPLOYMENT OF VERTICAL MOORING STRINGS WITHIN SATELITE TELEMETRY DATA ACQUISITION SYSTEMS WOULD SERVE FURTHER TO FACILITATE THE EXPLOITATION OF SUCH CONDUCTIVITY SENSORS.