Residual losses in a guard-ring micrometer-electrode holder for solid-disk dielectric specimens

Residual losses occurring in the specimen holder and in the bridge standard capacitor must be taken into account in order to make accurate bridge measurements of the dielectric losses of materials that have very low losses. Also, knowledge of the exact spacing of the electrodes is required for accurate determination of the dielectric constant of materials. To better meet these requirements, a new specimen holder has been designed and constructed. By a technique using ball reference gages, the electrodes of the holder can be adjusted to be parallel to about one micron, and the zero correction of the micrometer can be determined to ±1 micron. Using a modification of a technique used by Astin¹ and others, the residual loss angles of the holder and its connecting leads and of the bridge standard capacitor were determined to ±1 or 2 microradians.