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Time-domain reflectometry probe for water content and electrical conductivity measurements in saline porous media

Persson, Magnus LU ; Bendz, David LU and Flyhammar, Peter LU (2004) In Vadose Zone Journal 3(4). p.1146-1151
Abstract
A new coated time-domain reflectometry (TDR) probe design is described and evaluated. In contrast to previous coated TDR probes, our probe may be used to measure both the dielectric constant (K-a) and bulk electrical conductivity (sigma(a)) in saline porous media. This was made possible by attaching two coaxial cables to a 0.27-m three-rod with a coated central rod. The shield of the first cable was to one of the outer rods and the conductor was connected to the coated central rod. The conductor and shield of the other coaxial cable were connected to each of the two outer rods, respectively. Thus, our probe consists of two unbalanced, two-rod probes. The probe is called coated-uncoated probe (CUP). Four prototypes with two different... (More)
A new coated time-domain reflectometry (TDR) probe design is described and evaluated. In contrast to previous coated TDR probes, our probe may be used to measure both the dielectric constant (K-a) and bulk electrical conductivity (sigma(a)) in saline porous media. This was made possible by attaching two coaxial cables to a 0.27-m three-rod with a coated central rod. The shield of the first cable was to one of the outer rods and the conductor was connected to the coated central rod. The conductor and shield of the other coaxial cable were connected to each of the two outer rods, respectively. Thus, our probe consists of two unbalanced, two-rod probes. The probe is called coated-uncoated probe (CUP). Four prototypes with two different coating materials (i.e., polyolefin and kynar heat-shrink tubes) were evaluated. The probes were calibrated in several fluids having different K-a and sigma(a). The K-a measurement of the coated part the probe was successfully fitted to target K-a using a two-phase dielectric mixing model. Due to signal attenuation, measurements of K-a were not possible for sigma(a) higher than 9 dS m(-1) for the polyolefin-coated probes whereas the upper limits for the kynar-coated probes and the uncoated probe were 5 and 2.5 dS m(-1), respectively. Measurements of sigma(a) are only possible with the uncoated part. Measurements of K-a and sigma(a) were also taken during three upward infiltration experiments in sand using soil solution electrical conductivities of 0.01, 6.31, and 12.03 dS m(-1). For the uncoated part, K-a could not be measured when sigma(a) was higher than about 2 dS m(-1), whereas K-a measurements were possible using the coated part even when sigma(a) was 3 dS m(-1). (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Vadose Zone Journal
volume
3
issue
4
pages
1146 - 1151
publisher
Soil Science Society of America
external identifiers
  • wos:000227469200010
  • scopus:33746815146
ISSN
1539-1663
language
English
LU publication?
yes
id
87a03b22-8f9a-41af-a8ff-21ee948f32b4 (old id 249097)
alternative location
http://vzj.geoscienceworld.org/cgi/content/abstract/3/4/1146
date added to LUP
2007-10-29 15:35:32
date last changed
2017-01-01 06:59:57
@article{87a03b22-8f9a-41af-a8ff-21ee948f32b4,
  abstract     = {A new coated time-domain reflectometry (TDR) probe design is described and evaluated. In contrast to previous coated TDR probes, our probe may be used to measure both the dielectric constant (K-a) and bulk electrical conductivity (sigma(a)) in saline porous media. This was made possible by attaching two coaxial cables to a 0.27-m three-rod with a coated central rod. The shield of the first cable was to one of the outer rods and the conductor was connected to the coated central rod. The conductor and shield of the other coaxial cable were connected to each of the two outer rods, respectively. Thus, our probe consists of two unbalanced, two-rod probes. The probe is called coated-uncoated probe (CUP). Four prototypes with two different coating materials (i.e., polyolefin and kynar heat-shrink tubes) were evaluated. The probes were calibrated in several fluids having different K-a and sigma(a). The K-a measurement of the coated part the probe was successfully fitted to target K-a using a two-phase dielectric mixing model. Due to signal attenuation, measurements of K-a were not possible for sigma(a) higher than 9 dS m(-1) for the polyolefin-coated probes whereas the upper limits for the kynar-coated probes and the uncoated probe were 5 and 2.5 dS m(-1), respectively. Measurements of sigma(a) are only possible with the uncoated part. Measurements of K-a and sigma(a) were also taken during three upward infiltration experiments in sand using soil solution electrical conductivities of 0.01, 6.31, and 12.03 dS m(-1). For the uncoated part, K-a could not be measured when sigma(a) was higher than about 2 dS m(-1), whereas K-a measurements were possible using the coated part even when sigma(a) was 3 dS m(-1).},
  author       = {Persson, Magnus and Bendz, David and Flyhammar, Peter},
  issn         = {1539-1663},
  language     = {eng},
  number       = {4},
  pages        = {1146--1151},
  publisher    = {Soil Science Society of America},
  series       = {Vadose Zone Journal},
  title        = {Time-domain reflectometry probe for water content and electrical conductivity measurements in saline porous media},
  volume       = {3},
  year         = {2004},
}