AN OPTICAL FEEDBACK BASED HIGH ACCURACY BEAM TRANSMISSOMETER DEVELOPMENT

A LIGHT SOURCE WILL BE DEVELOPED USING OPTICAL FEEDBACK, AND WILL BE INCORPORATED INTO A LIGHT BEAM TRANSMISSOMETER TO DEVELOP A PROTOTYPE FOR EVENTUAL PRODUCTION OF A HIGH ACCURACY, WAVELENGTH SELECTABLE BEAM TRANSMISSOMETER. THE ACCURACY IN MEASUREMENT OF PARTICLE VOLUME CONCENTRATION WITH THE EXISTING RED LIGHT (660 NM WAVELENGTH). 25 CM TRANSMISSOMETER IS APPROXIMATELY THIRTY PARTS PER BILLION. TRANSMISSIOMETERS USING LOW POWER LIGHT EMITTING DIODES (LED'S), AT OTHER WAVELENGTHS ARE PRESENTLY INFEASIBLE DUE TO INSTABILITY AND LOW LIGHT OUTPUT. BY USING A SILICON DETECTOR WHICH HAS EXCELLENT STABILITY AND TEMPERATURE COEFFICIENT TO CONTROL THE LIGHT SOURCE (OPTICAL FEEDBACK), THE ACCURACY OF THE EXISTING RED LIGHT, 25 CM TRANSMISSOMETER. CONSEQUENTLY, THIS PROJECT WILL LAY THE GROUNDWORK FOR PRODUCTION OF WAVELENGTH SELECTABLE (I.E. USING GREEN, YELLOW, ORGANGE, AND THE NEWLY DEVELOPED BLUE LED) TRANSMISSOMETERS. THIS WILL ALLOW DETERMINATION OF THE CONTRIBUTION OF DISSOLVED, AS WELL AS SUSPENDED MATERIAL TO THE ATTENUATION OF LIGHT IN NATURAL WATERS. THE PROJECT WILL BE PERFORMED PRIMARILY AS A LABORATORY BASED PROGRAM OF PROTYTYPE DEVELOPMENT, CALIBRATION, AND TESTING, FOLLOWED BY A BRIEF ASSESSMENT OF OPERATION IN THE FIELD.