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@ARTICLE{Bogena:59685,
      author       = {Bogena, H. R. and Huisman, J. A. and Oberdörster, C. and
                      Vereecken, H.},
      title        = {{E}valuation of a low-cost soil water content sensor for
                      wireless network applications},
      journal      = {Journal of hydrology},
      volume       = {344},
      issn         = {0022-1694},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {PreJuSER-59685},
      pages        = {32 - 42},
      year         = {2007},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {Wireless sensor networks area promising new in situ
                      measurement technology for monitoring soil water content
                      changes with a high spatial and temporal resolution for
                      large areas. However, to realise sensor networks at the
                      small. basin scale (e.g. 500 sensors for an area of 25 ha),
                      the costs for a single sensor have to be minimised.
                      Furthermore, the sensor technique should be robust and
                      operate with a low energy consumption to achieve a long
                      operation time of the network. This paper evaluates a
                      tow-cost soil water content sensor (ECH2O probe model EC-5,
                      Decagon Devices Inc., Pullman, WA) using laboratory as well.
                      as field experiments. The field experiment features a
                      comparison of water content measurements of a forest soil at
                      5 cm depth using TDR and EC-5 sensors. The laboratory
                      experiment is based on a standardized sensor
                      characterisation methodology, which uses liquid standards
                      with a known dielectric permittivity. The results of the
                      laboratory experiment showed that the EC-5 sensor has good
                      output voltage sensitivity below a permittivity of 40, but
                      is less sensitive when permittivity is higher. The
                      experiments also revealed a distinct dependence of the
                      sensor reading on the applied supply voltage. Therefore, a
                      function was obtained that allows the permittivity to be
                      determined from the sensor reading and the supply voltage.
                      Due to the higher frequency of the EC-5 sensor, conductivity
                      effects were less pronounced compared to the older EC-20
                      sensor (also Decagon Devices Inc.). However, the EC-5 sensor
                      reading was significantly influenced by temperature changes.
                      The field experiment showed distinct differences between TDR
                      and EC-5 measurements that could be explained to a large
                      degree with the correction functions derived from the
                      laboratory measurements. Remaining errors are possibly due
                      to soil variability and discrepancies between measurement
                      volume and installation depth. Overall, we conclude that the
                      EC-5 sensor is suitable for wireless network applications.
                      However, the results of this paper also suggest that
                      temperature and electric conductivity effects on the sensor
                      reading have to be compensated using appropriate correction
                      functions. (C) 2007 Elsevier B.V. All rights reserved.},
      keywords     = {J (WoSType)},
      cin          = {ICG-4 / JARA-SIM},
      ddc          = {690},
      cid          = {I:(DE-Juel1)VDB793 / I:(DE-Juel1)VDB1045},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Engineering, Civil / Geosciences, Multidisciplinary / Water
                      Resources},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000250026600003},
      doi          = {10.1016/j.jhydrol.2007.06.032},
      url          = {https://juser.fz-juelich.de/record/59685},
}