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Abstract
This thesis describes a recent study to understand the actual long term behavior of the Zener diode standards belonging to The National Institute for Standards (NIS), Egypt. The Technical problem is: Can the behavior of the group of Zener diode standards simulates or corresponds with the same performance of the Reference standards? Can we rely on the mean value of this group as a reference value? This is the point. During the thesis, this task has been achieved on two different groups of Zener diode standards which were subjected for this study.
The mean value of the two groups has evaluated through two different methods. The first method depends on the direct measurement for the deviations in each unit of the two groups and the pivot unit to calculate the practical arithmetic mean of each group. The second one was applied to determine the same mean of the two groups but using the mathematical analysis by the least square method. The value of each unit of the group has been evaluated from this calculated mean. The suitable specified software had been implemented to perform all measurements. All precautions which minimize the resulted errors have been performed.