Precise determination of the area of guarded electrodes for accurate dielectric measurements on solid-disk specimens

Accurate measurements of dielectric properties of materials by the three-terminal air-gap method require accurate knowledge of the area of the electrodes. The two fluid method enables us to measure the dielectric constant of a specimen without knowledge of the area of the cell electrodes, or of the thickness of the specimen, if the electrode spacing and area remain constant during the set of four measurements required. But it is now known that the effective area is a function of the dielectric constant of the specimen being measured by this technique. The problem now is to determine the magnitude of this change of area, and evaluate its effect on the dielectric constants measured.