Fast Measurement Techniques for Research in Dielectrics

Measurement techniques for research in dielectrics require very fast time resolution and extremely wide dynamic ranges. Additionally, the measured quantities may be very low in amplitude. These conditions can be met only partly by electrical measuring systems. Additionally, two-dimenstional or even three-dimensional spatial information concerning the prebreakdown phenomena is highly desirable. This can only be achieved by optical measuring systems, which also may provide other advantages. In order to provide adequate time resolution, only coaxial measuring systems are considered. These consist of voltage probes using ohmic or capacitive networks and electro-optical devices. For current measurements ohmic shunts are compared with inductive probes and optical current probes. Optical measurement techniques based on high-speed photography are described in detail. In this context, the widely used streak-cameras are compared with framing cameras. It is obvious that research in dielectrics requires special highspeed recording systems which are not readily available. Together with recent image recording systems, however, very precise optical measurements are possible.