Simple method for determining cable length resistance in time domain reflectometry systems

Time domain reflectometry (TDR) based electrical conductivity (EC) measurements underestimate solution conductivity (sigma) 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 us. 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 an 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.