| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
George E. Brown Jr. Salinity Laboratory USDA-ARS, 450 W. Big Springs Rd., Riverside, CA 92507
* Corresponding author (pcastiglione{at}ussl.ars.usda.gov)
In time domain reflectometry (TDR), the ohmic resistance of the sample medium is related to the amplitude of the reflected signal at long time, once all the multiple reflections have taken place and steady state is achieved. Such a relationship, which permits measuring the sample electrical conductivity, is exact when no signal dissipation occurs other than in the sample. To account for signal attenuation along the coaxial cable, sample and cable are generally modeled as two resistors in series. In this work we review the fundamentals of the transmission line theory and demonstrate, both theoretically and experimentally, that such a formulation is incorrect. We propose a new simple procedure for the analysis of TDR signals based on a difference reflection method, by scaling the reflection coefficients with respect to one or more standards of known conductivity. The procedure was tested on 16 CaCl2 solutions, using two different TDR probes and two cable lengths. The experimental results are in excellent agreement with the theory.
Abbreviations: dc, direct content • EC, electrical conductivity • TDR, time domain reflectometry
This article has been cited by other articles:
|
|
 |
|
  C.-P. Lin, C.-C. Chung, J. A. Huisman, and S.-H. Tang Clarification and Calibration of Reflection Coefficient for Electrical Conductivity Measurement by Time Domain Reflectometry Soil Sci. Soc. Am. J., June 18, 2008; 72(4): 1033 - 1040. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. Huisman, C. P. Lin, L. Weihermuller, and H. Vereecken Accuracy of Bulk Electrical Conductivity Measurements with Time Domain Reflectometry Vadose Zone J., April 14, 2008; 7(2): 426 - 433. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C.-P. Lin, C.-C. Chung, and S.-H. Tang Accurate Time Domain Reflectometry Measurement of Electrical Conductivity Accounting for Cable Resistance and Recording Time Soil Sci. Soc. Am. J., June 29, 2007; 71(4): 1278 - 1287. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Regalado, A. Ritter, and R. M. Rodriguez-Gonzalez Performance of the Commercial WET Capacitance Sensor as Compared with Time Domain Reflectometry in Volcanic Soils Vadose Zone J., April 9, 2007; 6(2): 244 - 254. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Huisman and H. Vereecken Comments on "Time Domain Reflectometry Laboratory Calibration in Travel Time, Bulk Electrical Conductivity, and Effective Frequency" Vadose Zone J., October 3, 2006; 5(4): 1071 - 1072. [Full Text] [PDF]
|
|
|
|
|
|
S. R. Evett, J.A. Tolk, and T.A. Howell Response to "Comments on 'TDR Laboratory Calibration in Travel Time, Bulk Electrical Conductivity, and Effective Frequency'" Vadose Zone J., October 3, 2006; 5(4): 1073 - 1075. [Full Text] [PDF]
|
|
|
|
|
|
P. Castiglione, P. J. Shouse, and J. M. Wraith Multiplexer-Induced Interference on TDR Measurements of Electrical Conductivity Soil Sci. Soc. Am. J., August 3, 2006; 70(5): 1453 - 1458. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. B. Jones, R. W. Mace, and D. Or A Time Domain Reflectometry Coaxial Cell for Manipulation and Monitoring of Water Content and Electrical Conductivity in Variably Saturated Porous Media Vadose Zone J., October 10, 2005; 4(4): 977 - 982. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Kelleners, M. S. Seyfried, J. M. Blonquist Jr., J. Bilskie, and D. G. Chandler Improved Interpretation of Water Content Reflectometer Measurements in Soils Soil Sci. Soc. Am. J., September 29, 2005; 69(6): 1684 - 1690. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ritter, R. Munoz-Carpena, C. M. Regalado, M. Javaux, and M. Vanclooster Using TDR and Inverse Modeling to Characterize Solute Transport in a Layered Agricultural Volcanic Soil Vadose Zone J., May 12, 2005; 4(2): 300 - 309. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. B. Jones and D. Or Frequency Domain Analysis for Extending Time Domain Reflectometry Water Content Measurement in Highly Saline Soils Soil Sci. Soc. Am. J., September 1, 2004; 68(5): 1568 - 1577. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. A. Robinson, D. A. Robinson, S. B. Jones, J. M. Wraith, D. Or, and S. P. Friedman A Review of Advances in Dielectric and Electrical Conductivity Measurement in Soils Using Time Domain Reflectometry Vadose Zone J., November 1, 2003; 2(4): 444 - 475. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| The SCI Journals | Agronomy Journal | Crop Science | |||
| Vadose Zone Journal | Journal of Plant Registrations | ||||
| Journal of Natural Resources and Life Sciences Education |
Journal of Environmental Quality |
||||
