الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
One of the main aims of thermal metrology laboratory in National Institute for Standards (NIS-Egypt) is to establish the national standard for humidity. This provides the realization of dew/frost-point temperature scale and the response to an increasing number of requests for accurate calibration of chilled-mirror hygrometers. The present work describes construction and characterization of a dew/frost-point generator to work in the range from -50 oC to 0 oC. In the realized generator, the air flows through a saturator controlled by a regulated flow meter. The reference dew/frost-point temperature was measured by a Standard Platinum Resistance Thermometer (SPRT) connected to a resistance bridge. One of the outputs is the increase of the scope of measurements capability in NIS. In addition, this encourages the laboratory to develop and modify the generator for better efficiency to continue improving its uncertainty in the future. In this thesis, an intensive work has been performed during designing, fabrication, assembling and studying of the new NIS dew-point generator. Chapter one gives a historical background about humidity and the importance of humidity in the industrialized world science. It contains some definitions and terminology often used with regard to humidity beside calibrations of standards and transfer standards equipment used in humidity. Chapter two gives a view of previous researches regarding the thesis subject.Chapter three starts with studying the principle, preparation, designing and installation of the new generator. This chapter describes also developing software used to convert the measurements of SPRT on the resistance bridge into temperature. Full description of the working procedures was described as well.Chapter four starts with studying temperature stability of the generator. It contains a comparative study between the saturator temperature of the new generator and the dew/frost-point temperature of the chilled-mirror hygrometer. The system performance was tested and an evaluation of saturator efficiency was performed. This chapter also presents an analysis of the uncertainty budget describing all sources of uncertainty components and methods of evaluation. The chapter is ended with a table that summarizes all of the components, combined and expanded.