Improvements on the measurements of dielectric constant and dissipation factor in a wide frequency range

This paper describes an improved micrometer electrode system for the measurements of dielectric constant, dissipation factor, and mean thickness of sheet specimens in a wide frequency range and its appplication to a series of measuring methods. The influence of the edge capacitance and the residual impedance of this electrode system has been decreased to a negligibly small amount by the adoption of a shield ring and improvements in construction of the electrode system. The characteristics of the system are easily examined by using its electrode gap fine adjustment mechanism, which is developed for a series of measuring methods. In case the varying gap immersion method is adopted, the imperfect contact between the electrodes and the specimen and the residual impedance of the system do not affect the results, even at the highest frequency. Furthermore, the measurements are limited to only the gap variations and the resonance voltage ratio, and are freed from those of the electrode gap length, the electrode area, and the specimen thickness. Therefore, the measuring and calculating processes are so simplified that they take only a few minutes for each specimen, and in a series of methods, the best results are obtained without any correction in a wide frequency range from 1 to 200 MHz. The resolution is limited by the sensitivity and stability of the adopted apparatus such as a Q meter. The accuracy reaches ±0.2% for dielectric constant and ±2% or 3 μrad for dissipation factor, respectively, even at the highest frequency of 200 MHz.