Determination of the permittivity of soils by use of double transmission measurements

[摘要] Delay time measurements, e.g. time domain reflectometry(TDR), are a well-established method for the measurement ofpermittivity of various materials, especially soils. However,common measurement systems only provide one average value of thedielectric constant along the length of the TDR probe. Thiscontribution deals with an advanced application of the TDRprinciple, the so-called double transmission method, for thedetermination of the water content of soil along a probe. To applythe advanced TDR technique, a probe, realized by a combination ofa transmission line and a dielectric obstacle, which canmechanically be moved along the probe, is used. The probe isinserted into the soil to measure the effective soil permittivity.Thus, the water content along the probe can be estimated by meansof the effective permittivity. Based on the known mechanicalposition of the reflection at the end of the probe and theposition of the obstacle, the measured delay time can be used as ameasure for the effective dielectric constant of the environmentsurrounding the obstacle. Thus, it is possible to determine theeffective dielectric constant with a spatial resolution given bythe step size of the obstacle displacement.

[学科分类] 电子、光学、磁材料