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This article in SSSAJ

  1. Vol. 65 No. 1, p. 13-18
     
    Received: Nov 30, 1999


    * Corresponding author(s): derosny@ccr.jussieu.fr
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doi:10.2136/sssaj2001.65113x

Numerical Modeling of a Capacitance Probe Response

  1. G. de Rosny *a,
  2. A. Chanzyb,
  3. M. Pardéb,
  4. J-C. Gaudub,
  5. J-P. Frangia and
  6. J-P. Laurentc
  1. a Laboratoire Environnement et Développement, Université Paris 7, 2 place Jussieu, F-75251 Paris Cedex 05, France
    b INRA, Unité de Science du Sol, Domaine St Paul, F-84914 Avignon Cedex 09, France
    c Laboratoire d'étude des Transferts en Hydrologie et Environnement, BP53, F-38041 Grenoble Cedex 09, France

Abstract

Capacitance sensors are one of the common means of characterizing the soil dielectric constant. Their design depends on their expected applications. In particular, the electrode geometry has a critical influence on the extension of the probed region. Moreover, the soil may not always be viewed as a medium of statistically uniform dielectric constant (because of packing effects, air sheath in the vicinity of the electrodes, stones). Numerical modeling for the behavior of a particular probe was developed. It is based on solutions of the Maxwell's equations in the quasi-static approximation, by a finite element method. This modeling was compared with laboratory measurements in various media (air, ethanol) where heterogeneity was inserted in the vicinity of the electrode. The numerical model reproduces very well the probe response when millimetric scale perturbations were introduced. The numerical model appears to be a promising tool to investigate more deeply the capacitance probe measurements, for instance the extension of the measurement volume or the significance of measurements in highly structured soils.

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Copyright © 2001. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.65:13–18.