% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Bechtold:9528,
      author       = {Bechtold, M. and Huisman, J. A. and Weihermüller, L. and
                      Vereecken, H.},
      title        = {{A}ccurate determination of the bulk electrical
                      conductivity with the {TDR}100 cable tester},
      journal      = {Soil Science Society of America journal},
      volume       = {74},
      issn         = {0361-5995},
      address      = {Madison, Wis.},
      publisher    = {SSSA},
      reportid     = {PreJuSER-9528},
      pages        = {495 - 501},
      year         = {2010},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {Time domain reflectometry (TDR) is commonly used to
                      determine the soil bulk electrical conductivity. To obtain
                      accurate measurements, the three parameters of a series
                      resistor model (probe constant, K-p; cable resistance, R-C;
                      and remaining resistance, R-0) are typically calibrated
                      using liquids with known electrical conductivity. Several
                      studies have reported discrepancies between calibrated and
                      directly measured parameters of the series resistor model.
                      In this study, we examined the possibility that a technical
                      issue with the TDR100 cable tester contributed to part of
                      these inconsistencies. Our results showed that with an
                      increasing level of waveform averaging, the reflection
                      coefficient, as well as K-p, R-C, and R-0, approached a
                      maximum value. A comparison with independently determined
                      values indicated that a high level of waveform averaging
                      provided the physically most plausible results. Based on our
                      results, we propose averaging at least 16 waveforms, each
                      consisting of at least 250 points. An oscilloscope-based
                      signal analysis showed that the increase in the reflection
                      coefficient with increasing waveform averaging in saline
                      media is related to a capacitance associated with electrode
                      polarization in combination with a change in the pulse
                      period of the pulse train when the TDR100 starts collecting
                      data points. This capacitance resulted in a slow change of
                      the average voltage in the TDR pulse train until a stable
                      average voltage was reached. Higher levels of waveform
                      averaging cancel the impact of the first erroneous voltage
                      measurements out. In practical applications, the errors in
                      the determination of the bulk electrical conductivity can be
                      as high as $5\%$ for the low-conductivity range (<0.1 S
                      m(-1)) and up to $370\%$ in saline media (1.4 S m(-1)) when
                      waveform averaging is changed after calibration.},
      keywords     = {J (WoSType)},
      cin          = {ICG-4 / JARA-ENERGY},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB793 / $I:(DE-82)080011_20140620$},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Soil Science},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000275187300018},
      doi          = {10.2136/sssaj2009.0247},
      url          = {https://juser.fz-juelich.de/record/9528},
}