
Metrology: standards 209
pacitor (Zickner, 1930). A screen electrode is inserted in the gap between the
active electrodes and intercepts the electric flux. A hole, or some holes in the
screen electrode, allows a small portion of the flux between active electrodes to
flow. Parallel-plate or cylindrical (see Fig. 8.25) geometry is typical; often, the
screen electrode is removable and a set of plug-in electrodes, having holes of
different sizes, are provided to obtain different capacitance values. The same
(a) (b)
Figure 8.25
A Zickner capacitor, realized in cylindrical geometry. The capacitor (a) has two
coaxial electrodes (the spike and the inner of the hole ...