INHERENTLY CALIBRATED FIBER OPTIC SENSORS FOR MEASURING SEAWATER PH

THE WORLD'S OCEANS MAY ABSORB A LARGE PART OF THE CO2 EMISSIONS GENERATED BY BURNING FOSSIL FUELS, THEREBY LESSENING THE GREENHOUSE EFFECT. HOWEVER, MEASURING THIS GLOBAL PROCESS WILL REQUIRE HIGHLY ACCURATE, PRECISE NEW CHEMICAL SENSORS THAT CAN OPERATE UNATTENDED FOR LONG PERIODS ON BUOYS DEPLOYED AT SEA. THIS PROJECT WILL DEVELOP A FIBER OPTICAL PH SENSOR AND INSTRUMENT PACKAGE THAT DOES NOT REQUIRE CALIBRATION WITH EXTERNAL STANDARDS AND THEREFORE CAN OPERATE UNATTENDED. THE INHERENTLY CALIBRATED SENSOR IS MADE POSSIBLE BY A PROPRIETARY PROCESS THAT PRODUCES THIN, PHYSICALLY RESILIENT TRANSPARENT FILMS OF PH INDICATOR DYES. OPTICAL ABSORBANCE MEASUREMENTS MADE AT MULTIPLE WAVELENGTHS WILL PROVIDE ACCURATE ( 0.001 PH UNITS) AND PRECISE PH MEASUREMENTS FREE FROM THE DRIFT DISPLAYED BY CONVENTIONAL PH ELECTRODES. PHASE I WILLDEMONSTRATE THAT THE IMMOBILIZED DYES, BECAUSE THEY HAVE OPTICAL PROPERTIES AND ACID/BASE CHEMISTRIES THAT ARE SIMILAR TO DYES IN SOLUTION, ARE THEREFORE CAPABLE OF INHERENT CALIBRATION. PHASE II WILL DEVELOP AN INSTRUMENT THAT CAN EXPLOIT THE BENEFITS OF INHERENT CALIBRATION. THE SELF-CALIBRATING INSTRUMENT WILL BE CONSTRUCTED USING LOW-POWER COMPOSITE METAL-OXIDE SEMI-CONDUCTOR TECHNOLOGY ONA CIRCUIT BOARD THAT CAN BE PLUGGED INTO A PERSONAL COMPUTER (PC). MULTIPLEXING WILL ALLOW SEVERAL PH SENSORS TO USE A SINGLE LINEAR DIODE ARRAY DETECTOR. INTERNAL SHUT-DOWN SOFTWARE WILL SCHEDULE MEASUREMENTS AROUND LOW CURRENT IDLE PERIODS SO THAT LONG-TERM, UNATTENDED OPERATIONON BUOYS AT SEA WILL BE POSSIBLE USING SOLAR TRICKLE RECHARGING OF THE POWER SUPPLY. THE SENSORS AND INSTRUMENT PACKAGE WILL ALLOW OCEANOGRAPHERS TO DEPLOY LARGE NUMBERS OFSENSORS FOR EXTENDED PERIODS AND WILL PROVIDE THE DATA NECESSARY TO MEASURE OCEANS' RESPONSE TO ANTHROPOGENIC INPUTS OF CO2.