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Experimental Limitations of Time Domain Reflectometry Hardware for Dispersive Soils
Author(s) -
Logsdon S. D.
Publication year - 2006
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2005.0176n
Subject(s) - reflectometry , balun , waveform , multiplexer , time domain , attenuation , bandwidth (computing) , soil water , acoustics , frequency domain , materials science , electronic engineering , computer science , environmental science , optics , multiplexing , electrical engineering , soil science , physics , telecommunications , engineering , voltage , antenna (radio) , computer vision
Time domain reflectometry (TDR) has been used to determine soil water content. Multiple attachments and long cables may result in unreliable data for dispersive soils, but these attachments are necessary for automated field monitoring at multiple sites and depths. The objective of this study was to experimentally determine the effect of attachments on the TDR waveform for a parallel probe with a balun. The probe with parallel waveguides and balun was successively attached to the front panel of the cable tester (Level 1), to a transient suppressor (Level 2), to the first level multiplexer (Level 3), or to a second level multiplexer (Level 4). Each attachment level significantly reduced frequency bandwidth, and Level 4 frequency bandwidth was about half that of Level 1. The greatest attenuation decrease was between Levels 1 and 2. Attenuations due to TDR hardware make it difficult to obtain useful waveforms for determining soil water content.