Open AccessSingle‐Rod Probes for Time Domain Reflectometry: Sensitivity and Calibration
Author(s) -
Nussberger Mathis,
Benedickter Hansruedi,
Bächtold Werner,
Flühler Hannes,
Wunderli Hans
Publication year - 2005
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2004.0093
Subject(s) - reflectometry , materials science , calibration , rod , sensitivity (control systems) , dielectric , optics , coating , time domain , optoelectronics , composite material , physics , electronic engineering , medicine , alternative medicine , pathology , quantum mechanics , computer science , engineering , computer vision
Time domain reflectometry (TDR) probes consisting of one conducting rod and a wave mode converter are an alternative configuration that overcomes some of the disadvantages of conventional probes. We examined four different single‐rod probes (SRPs) and a two‐rod probe for sensitivity to a small and a large conductive scatterer in their vicinity. The SRPs were assembled combining a small and large wave mode converter with an uncoated and coated rod. We found that the volume sampled by SRPs is larger and more symmetric than in the case of a two‐rod probe of equal size. A comparison of the mode converters showed a higher loss for the smaller converter but only a small difference concerning the spatial sensitivity. Coating the conducting rod with a high dielectric constant material reduces the spatial sensitivity. One of the SRPs and the two‐rod probe were calibrated in a sand tank (particle size 0.08–0.2 mm) with volumetric water content up to 0.35 m 3 m −3 . The calibration showed only small differences in the measured bulk dielectric constant between the single‐rod and the two‐rod probe. Based on this study the SRP is a promising new tool for improved TDR measurement of soil moisture.