Probe Length Effects on Thermally-Biased TDR Measurements

Time-Domain Reflectometry (TDR) is a well-established technique for continuous, in-situ measurement of volumetric water content in field soils. Recent studies have shown that errors in the measurement of the soil dielectric constant may occur due to thermal variations present in the soil medium. These temperature effects in turn influence the determination of volumetric water content and must first be corrected for. The effect of TDR probe length, at ambient temperature conditions only, has also been investigated with results indicating a pronounced shift in measured waveform activity. This work presents a laboratory investigation of the extent of TDR probe length influence within volumetric water content measurements using probes subjected to a wide range of moisture content and thermal-variation scenarios.