Method for measuring properties of sheet- or foil-like materials of low electrical conductivity

摘要

A non-contact method and apparatus for determining the moisture content of sheet- or foil-like materials (1) of high moisture content and low electrical conductivity uses a transducer comprising ground planes (3) arranged on both sides of the material (1) to be measured, and at least one center conductor (2) arranged between each ground plane (3) and the material (1) to be measured approximately parallel to the material (1) in order to form a quasi-TEM transmission line resonator. Electromagnetic RF energy is fed into the quasi-TEM transmission line resonator so that the quasi-TEM waves propagate in the plane of the material (1) to be measured, and the resonator supports for the transverse and longitudinal waves such resonant modes whose resonant frequencies and Q's are dependent on the properties of the material (1) to be measured. The resonant frequencies and related Q's are measured, and these are used for determining the complex dielectric constant of the material (1) to be measured or, alternatively, the characteristics related to them.