Wide-frequency-range dielecteric spectrometer

Abstract

Newly developed techniques are described for the automated measurement and display of the relative permittivity and loss factor of insulating materials over the frequency range 10⁻⁴ to 10⁶Hz. The principle of operation is to sample, at logarithmically spaced times, the charge-time response to a voltage step of a capacitor containing a specimen of the material. Approximate transforms, developed for this application, are then applied to these data and the steady-state material parameters are presented as a permanent record in analogue form at discrete frequencies spaced at octave intervals. Apart from a brief initial setting-up operation, the process is automatic, and the time taken to describe a complete spectrum is 40s for one instrument which covers the frequency range 1 to 10⁶Hz; in about 15min another covers 10⁻⁴ to 10²Hz. The present embodiments are most suited to materials having loss factors greater than about 10⁻³. Factors limiting accuracy and resolution are discussed.