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@ARTICLE{Zimmermann:863487,
      author       = {Zimmermann, E. and Huisman, J. A. and Mester, A. and van
                      Waasen, S.},
      title        = {{C}orrection of phase errors due to leakage currents in
                      wideband {EIT} field measurements on soil and sediments},
      journal      = {Measurement science and technology},
      volume       = {30},
      number       = {8},
      issn         = {0022-3735},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {FZJ-2019-03541},
      pages        = {084002 -},
      year         = {2019},
      abstract     = {Electrical impedance tomography (EIT) is a promising method
                      to characterize important hydrological properties of soil,
                      sediments, and rocks. The characterization is based on the
                      analysis of the phase response of the complex electrical
                      conductivity in a broad frequency range (i.e. mHz to kHz).
                      However, it is challenging to measure the small phase
                      response of low-polarizable soils and rocks in the higher
                      frequency range up to 10 kHz. In order to achieve the
                      required phase accuracy in the kHz frequency range, an
                      optimized measurement system and advanced model-based
                      processing methods have been developed. Recently, EIT
                      measurements at sites with low electrical conductivity have
                      shown a new dominating phase error related to capacitive
                      leakage currents between cable shields and soil. In order to
                      correct this phase error, we developed an advanced finite
                      element model that considers both leakage currents and
                      capacitive coupling between the soil and the cable shields
                      in the reconstruction of the complex electrical conductivity
                      distribution. This advanced model also takes into account
                      potential measurement errors due to high electrode
                      impedances. The use of this advanced model reduced the new
                      dominating error for media with low electrical conductivity.
                      It was also found that the amount of leakage current is an
                      additional indicator for data quality that can be used for
                      data filtering. After application of a novel data filter
                      based on the leakage current and the use of the advanced
                      modelling approach, the phase error of the measured transfer
                      impedances above 100 Hz was significantly reduced by a
                      factor of 6 or more at 10 kHz. In addition, physically
                      implausible positive phase values were effectively
                      eliminated. The new correction method now enables the
                      reconstruction of the complex electrical conductivity for
                      frequencies up to 10 kHz at field sites with a low
                      electrical conductivity.},
      cin          = {ZEA-2 / IBG-3},
      ddc          = {620},
      cid          = {I:(DE-Juel1)ZEA-2-20090406 / I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000475979700002},
      doi          = {10.1088/1361-6501/ab1b09},
      url          = {https://juser.fz-juelich.de/record/863487},
}