The aim of this work has been to design and test a refractometer for accurate measurement of seaw... more The aim of this work has been to design and test a refractometer for accurate measurement of seawater refractive index. The goal was to create a refractometer with a cylindrical embodiment and measure refractive indices with an accuracy of 10 −6 refractive index units (RUI). The realization of the instrument resulted in a measurement chamber consisting of a cylindrical glass tube with an inner radius if 4 mm, thickness of 1 mm and length of 115 mm. To transverse the laser beam into the glass cylinder in a satisfactory way, the beam is directed by mirrors submerged in an immersion oil. The oil functions as a "compensating" medium between the air-glass interface and was only used because desired embodiments were not available. The final refractometer design was decided after rigorous computer simulations. The experiments were conducted by measuring the laser beam displacement of sodium chloride solutions, with salinities ranging from 0 to 40 parts per thousand. A brief temperature measurement was also conducted. The results revealed that the instrument was able to short-term measurements with an accuracy of 1.5⋅10 −5 RIU, but poor repeatability of the instrument decreased the overall accuracy to 2.9⋅10 −4 RIU. The increased uncertainties is considered to be caused by either small displacements in the tweakable components in the setup or by slow drifts in the laser/detector caused by heating processes. i I would first like to thank my supervisor, professor Lars Egil Helseth, for engagement, guidance and support through this last year's period of work. My thanks also to Xiaodong Guo for helping with the vaporising system. And to the institute workshop for making important parts for my setup. Thanks also to Jostein Hovdenes (AADI), Jon Hellevang (CMR), Peter Thomas (CMR), and Benny Svardal (CMR) for a rewarding and interesting meeting, where the basic design idea of the setup first arose. At last, thanks to my fellow students, friends and family, especially my sister, for their help and support.
The aim of this work has been to design and test a refractometer for accurate measurement of seaw... more The aim of this work has been to design and test a refractometer for accurate measurement of seawater refractive index. The goal was to create a refractometer with a cylindrical embodiment and measure refractive indices with an accuracy of 10 −6 refractive index units (RUI). The realization of the instrument resulted in a measurement chamber consisting of a cylindrical glass tube with an inner radius if 4 mm, thickness of 1 mm and length of 115 mm. To transverse the laser beam into the glass cylinder in a satisfactory way, the beam is directed by mirrors submerged in an immersion oil. The oil functions as a "compensating" medium between the air-glass interface and was only used because desired embodiments were not available. The final refractometer design was decided after rigorous computer simulations. The experiments were conducted by measuring the laser beam displacement of sodium chloride solutions, with salinities ranging from 0 to 40 parts per thousand. A brief temperature measurement was also conducted. The results revealed that the instrument was able to short-term measurements with an accuracy of 1.5⋅10 −5 RIU, but poor repeatability of the instrument decreased the overall accuracy to 2.9⋅10 −4 RIU. The increased uncertainties is considered to be caused by either small displacements in the tweakable components in the setup or by slow drifts in the laser/detector caused by heating processes. i I would first like to thank my supervisor, professor Lars Egil Helseth, for engagement, guidance and support through this last year's period of work. My thanks also to Xiaodong Guo for helping with the vaporising system. And to the institute workshop for making important parts for my setup. Thanks also to Jostein Hovdenes (AADI), Jon Hellevang (CMR), Peter Thomas (CMR), and Benny Svardal (CMR) for a rewarding and interesting meeting, where the basic design idea of the setup first arose. At last, thanks to my fellow students, friends and family, especially my sister, for their help and support.
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