Wide-frequency-range dielecteric spectrometer

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.