how to measure dielectric permittivity?

Answer 1

The dielectric constant of a material can be found by a variety of static electrical measurements. The complex permittivity is evaluated over a wide range of frequencies by using different variants of dielectric spectroscopy, covering nearly 21 orders of magnitude from 10−6 to 1015 Hz. Also, by using cryostats and ovens, the dielectric properties of a medium can be characterized over an array of temperatures. In order to study systems for such diverse exciting fields, a number of measurement setups are used, each adequate for a special frequency range.

* Low-frequency time domain measurements (10−6−103 Hz)
* Low-frequency frequency domain measurements (10−5−106 Hz)
* Reflective coaxial methods (106−1010 Hz)
* Transmission coaxial method (108−1011 Hz)
* Quasi-optical methods (109−1010 Hz)
* Fourier-transform methods (1011−1015 Hz)

Answer 2

Imagine a dielectric cube placed in electric field E along with one side. Dielectric molecules polarize creating an opposite field kE. Therefore, the field within the dielectric D = E - kE = eE (where I used e instead of epsilon). e = eps*e' where eps is permittivity of a vacuum and e' is called relative permittivity. To measure e you can cut a little narrow hole with the large side perpendicular to E. If you put two electrodes along the large sides in the hole, the charge on the electrode will be proportional to the field D and area of the electrode, Q=D*S. Now you can measure Q by galvanometer and by dividing it by S obtain your result.

Answer 3

you take an empty capacitor measure its capacitance.Lete be Ce
Fill it with substance (whose dielectric permittivity you want to measure).Let it be Cs.
Then dielectric permittivity of subsance is
(Cs-Ce)/Ca +1
where Ca is geometric capacitance of the capacitor.