Electrical characterization of the materials by a short electric probe

Many researchers have used the open-ended coaxial lines for measuring the complex permittivity of materials nondestructively. In this method, the material under test is placed against the open end of a coaxial line and its input reflection coefficient is recorded. An electrical equivalent model is then used for determining the complex permittivity of the terminating material. In general, this procedure is found satisfactory for a wide range of materials. However, the measurement error is found to be relatively large for the low permittivity liquids. As indicated by the experimental results, this occurs mainly due to a bad electrical contact of the coaxial sensor with the sample. An appreciable reduction in the error is observed when a small length of the inner conductor extends beyond the coaxial aperture plane. The results of the author´s investigation of this problem are presented