Abstract
This paper describes the construction, principle, and features of a precise variable capacitor with which it is possible to change the capacitance from 10-6pF to 10-2pF.
This precise variable capacitor, capable of obtaining a very small capacitance change, is different in its construction from an ordinary mechanical capacitor, and the merit of this capacitor is that it consists of multilayer disks of silica glass.
Using this structure, the variation of capacitance between two parallel plate electrode is reduced to an extremely small value of capacitance chage.
For example, in our experiments, a variation of 1×10-6pF was obtained by the displacement of 10μm of the earth-side movable electrode. Other merits of this capacitor are as follows.
No.1 The magnitude of capacitance change is determined by selecting the constant of glass disk.
No.2 The total dielectric losses of this capacitor is negligibly small.
No.3 This can be used in the very high freaquency range (1MHz∼300MHz), because no lead wires are needed in its construction.
This can also be applied for the measurement of dielectric properties of very thin film (several hundred Å) and for precise measurement of relative permitivity of various kinds of gases.
