Measurement of the dielectric properties of low-loss materials

A method described in 1957 has been improved, to allow measurement of the power factor of sheet specimens to within about ±5×10¿6 at frequencies from about 1 kc/s to 1 Mc/s, while the permittivity can be measured to within about ±0.1%, the uncertainty being contributed mainly by that in measuring the thickness of the specimen. The specimen is placed loosely in the micrometer-controlled electrode system, which includes a guard electrode; the system is adjusted to give the same capacitance with the specimen in position as it originally had without it. An electrode system on similar principles is available for cylindrical specimens. The possible sensitivity of the bridge network has been improved by interchanging the oscillator and detector.