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Simple Method for Determining Cable Length Resistance in Time Domain Reflectometry Systems
Author(s) -
Reece C. F.
Publication year - 1998
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/sssaj1998.03615995006200020003x
Subject(s) - reflectometry , equivalent series resistance , time domain , electrical resistivity and conductivity , materials science , conductivity , electrical engineering , physics , computer science , voltage , engineering , computer vision , quantum mechanics
Time domain reflectometry (TDR) based electrical conductivity (EC) measurements underestimate solution conductivity (σ) as salinity increases unless a correction parameter, R cable , is incorporated into the EC calculation. The parameter R cable accounts for series resistance of cable, connectors, and cable tester. The main objective of this study was to propose and verify a simple method of directly measuring R cable from the load resistance on waveguides that are shorted together. Also, the dependence of R cable on cable length vs. other resistances was investigated. The parameter R cable was found to be a function of cable length and a constant probe resistance. Errors caused by ignoring R cable in EC determinations increased with both salinity and series resistance. Although there may be cases where R cable has a negligible effect on EC determinations, there are also situations where it is important. This study shows that the measurement of R cable is so simple that there is little reason not to routinely incorporate it in all TDR‐based EC determinations.