The simple answer is yes, the dielectric constant is usually measured by
measuring the capacitance of a parallel-plate capacitor with a
standard/known dielectric, then switching to the "unknown" dielectric.
However there are complications.
(1) This works most easily with liquids and gases because it is easy to keep
a fixed set of capacitor plates and change from one dielectric to another
dielectric if the standard and the unknown are liquids or gases (or vacuum).
If the substance to be determined is a solid, it can be difficult to get the
substance to fill the gap entirely unless the capacitor plates are squeezed
into the dielectric. There are various tricks for getting around this.
(2) The capacitance measurement is often a frequency measurement with the
measuring cell's capacitance being used as part of an oscillator circuit.
There are various designs for this. However, the dielectric constant is
frequency dependent so you can get a range of answers depending upon the
frequency of the measuring device.
(3) The dielectric constant is also temperature dependent so you need to
operate the system at a controlled temperature.
Whether you need to worry about (2) and (3) depends on how much accuracy you
want.
Having come from a chemical-physics background I can tell you that physical
chemists have made many dielectric-constant measurements of liquids and
gases, and you can find more information about this in some physical
chemistry lab manuals. Procedures for solids are more difficult to find, so
once when I needed a value for a solid, I had to do some searching to figure
out the best way to measure it. I did use a parallel-plate capacitor, but
rather than exclude the air (difficult to do) I measured the capacitance as
a function of plate separation with a fixed thickness of dielectric between
the plates. That means "the capacitor" is really two capacitors in series,
one with fixed thickness of my unknown dielectric, the other of varying
thickness with air as the dielectric. The data were manually (computer)
least-squares fit against the series-capacitor equation with the unknown
dielectric constant as the varied parameter in the least-squares fit. This
worked so well that I have my physics class do this as a lab experiment.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817