A Noncontact Method for Dielectric Measurements

An instrument has been developed for measuring the dielectric permittivity and loss of a material without contacting electrodes from the mechanical torque generated by an electric field applied to a suitably shaped specimen. The theory of operation is briefly outlined, and it is shown that in principle the sensitivity of the method is independent of frequency. The design and operation of the instrument, which works over a frequency range of 0.001 c/s to 80 kc/s, is described in detail. An assessment of the precision of the method is made from dielectric loss measurements on polymethyl methacrylate and polystyrene spheres.