A dielectric spectrometer has been developed which employs Fourier analysis methods for an accurate, straightforward determination of the complex dielectric constants of solid and liquid polymeric materials in the frequency range 10-10(5) Hz between 120 and 770 K. On application of an electric field to the sample, the response of the sample is the electric displacement which is collected by the current detector circuit. The amplitude and phase relation between the applied electric field and the collected current is analysed using a Fourier transformation circuit and output as the complex dielectric constant. The structure and performance of the apparatus are described in detail. An example of a dielectric measurement using Nylon 6 films, where the effect of moisture on the dielectric relaxations has been studied, is presented. The activation energy of the observed alpha-relaxation has been calculated using commercial software.