Dielectric measurements at radio frequencies in the presence of a strong static field

Abstract

A differential dielectric bridge is described for the measurement of small changes in the real and imaginary part of the dielectric permittivity effected by the application of a strong static field to a liquid. The apparatus is based on the resonant bridge principle and operates in the rf range (0.7−120 MHz). A dc field up to 250 kV/cm can be superimposed on the rf field. Chemical increments in the dielectric loss factor characteristic for chemical relaxation experiments of less than 1×10⁻⁷ are detectable. The apparatus can also be used as a conventional dielectric bridge whereby changes in the real part of 5×10⁻⁵ and in the imaginary part of the permittivity as low as 1×10⁻⁴ are measurable. The technique of the measurements is discussed and illustrative examples are provided.