Tangent Line/Second‐Order Bounded Mean Oscillation Waveform Analysis for Short TDR Probe

Wang, Zhuangji; Lu, Yili; Kojima, Yuki; Zhang, Meng; Chen, Yan; Horton, Robert

doi:10.2136/vzj2015.04.0054

Cited by 17 publications

(21 citation statements)

References 18 publications

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“…New TDR waveform analysis techniques and the use of thermo‐frequency domain reflectometry (thermo‐FDR) may provide solutions to this problem. For instance, Z. Wang et al (, ) obtained promising soil water contents by combining the tangent line methods and the second‐order bounded mean oscillation method to determine the reflection points of thermo‐TDR waveforms. The potential to address the problem of the short physical length of thermo‐TDR probes using thermo‐FDR will be discussed in section .…”

Section: Probe Design and Constructionmentioning

confidence: 99%

Development and Application of the Heat Pulse Method for Soil Physical Measurements

Dyck

Horton

et al. 2018

Reviews of Geophysics

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117

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Accurate and continuous measurements of soil thermal and hydraulic propertiesare required for environmental, Earth and planetary science, and engineering applications, but they are not practicallyobtained by steady-state methods. The heat pulse (HP) method is a transient method for determinationof soil thermal properties and a wide range of other physical properties in laboratory and field conditions. The HP method is based on the line-heat source solution of the radial heat flow equation. This literature review begins with a discussion of the evolution of the HP method and related applications, followed by the principal theories, data interpretation methods and their differences. Important factors for HP probe construction are presented. The properties determined in unfrozen and frozen soilsare discussed, followed by a discussion of limitations and perspectives for the application of this method. The paper closes with a brief overview of future needs and opportunities for further development and application of the HP method.Keywords thermal properties, thermal conductivity, thermal resistivity, heat capacity, thermal diffusivity, thermal inertia, dual probe heat pulse, thermal probe, hot-wire method, fiber optics, distributed temperature sensing (DTS), thermo-time/frequency domain reflectometry (thermo-TDR, thermo-FDR), soilwater content, ice content, frozen soils, instrumentation DisciplinesAgricultural Science | Agriculture | Hydrology | Soil Science Comments This is a manuscript of an article published as He, Hailong, Miles F. Dyck, Robert Horton, Tusheng Ren, Keith L. Bristow, Jialong Lv, and Bingcheng Si. "Development and application of the heat pulse method for soil physical measurements." Reviews of Geophysics (2018) This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1029/2017RG000584 © 2018 American Geophysical Union. All rights reserved.Development and application of the heat pulse method for soil physical properties in laboratory and field conditions. The HP method is based on the line-heat source solution of the radial heat flow equation. This literature review begins with a discussion of the evolution of the HP method and related applications, followed by the principal theories, data interpretation methods and their differences. Important factors for HP probe construction are presented. The properties determined in unfrozen and frozen soilsare discussed, followed by a discussion of limitations and perspectives for the application of this method. The paper closes with a brief overview of future needs and opportunities for further development and application of the HP method.

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Section: Probe Design and Constructionmentioning

confidence: 99%

Development and Application of the Heat Pulse Method for Soil Physical Measurements

Dyck

Horton

et al. 2018

Reviews of Geophysics

Self Cite

117

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“…The TL‐BMO method can be used to determine the reflection positions in TDR waveforms (Wang et al, 2015). It is a prediction‐correction model based on a combination of the tangent line method and the second‐order BMO method.…”

Section: Methodsmentioning

confidence: 99%

“…The small sensing volume of the thermo‐TDR design makes it suitable for fine‐scale measurements, but in some cases restricts the representativeness of actual field conditions. In addition, short probes can limit the accuracy and precision of TDR measurements (Noborio, 2001; Schwartz et al, 2014; Wang et al, 2015). Topp et al (1984) reported that the errors in TDR θ with a 0.05‐m‐long probe were significant, with a standard deviation of 0.037 m 3 m −3 , while an improved accuracy was observed for sensors with longer probes.…”

mentioning

confidence: 99%

“…Kamai et al (2015) showed that errors in soil heat capacity ( C ) estimations were reduced significantly by using a large heater probe ( d = 2.38 mm) with a thick tubing wall and adoption of the ICPC theory. Wang et al (2015) proposed a tangent line/second‐order bounded mean oscillation (TL‐BMO) approach to determine the reflection positions of TDR waveforms, which increased the accuracy of the relative dielectric permittivity ( K a ) and θ results. However, these theories have not been fully integrated into the thermo‐TDR system.…”

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confidence: 99%

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An Improved Thermo‐TDR Technique for Monitoring Soil Thermal Properties, Water Content, Bulk Density, and Porosity

Peng

Xie

et al. 2019

Vadose Zone Journal

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Core Ideas A new thermo‐TDR sensor can determine soil thermal properties, water content, bulk density, porosity, and air‐filled porosity. The new theories are used to analyze the heat‐pulse data and TDR waveforms. The new sensor provides greater sensing volume and more accurate results than previous designs. The thermo‐time domain reflectometry (thermo‐TDR) technique is valuable for monitoring in situ soil water content (θ), thermal properties, bulk density (ρb), porosity (n), and air‐filled porosity (na) in the vadose zone. However, the previous thermo‐TDR sensor has several weaknesses, including limited precision of TDR waveforms due to the short probe length, small measurement volume, and thermal property estimation errors resulting from finite probe properties not accounted for by the heat pulse method. We have developed a new thermo‐TDR sensor design for monitoring θ, thermal properties, ρb, n, and na. The new sensor has a robust heater probe (outer diameter of 2.38 mm and length of 70 mm) and a 10‐mm spacing between the heater and sensing probes, which provides a sensing volume three times larger than that of the previous sensor. The identical cylindrical perfect conductors and the tangent line–second‐order bounded mean oscillation theories were applied to analyze the raw data. Laboratory tests showed that θ values determined with the new sensor had a RMSE of 0.014 m3 m−3 compared with 0.016 to 0.026 m3 m−3 with the previous sensor. Soil thermal property estimates with the new sensor agreed well with modeled values. Soil ρb, n, and na derived from θ and thermal properties were consistent with those derived from gravimetric measurements. Thus, the new thermo‐TDR sensor provides more accurate θ, thermal properties, ρb, n, and na values than the previous sensor.

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“…Several methods are available to improve the performance of T-TDR sensors. Using an expensive cable tester or oscilloscope with a short rise time (≤200 ps) (Kelly et al, 1995) and performing data smoothing and filtering analysis on the waveforms (Wang et al, 2016) can improve TDR waveform analysis for short probes. To minimize probe deflection, Kamai et al (2015) made robust probes by increasing their diameter.…”

Section: Introductionmentioning

confidence: 99%

An in situ probe‐spacing‐correction thermo‐TDR sensor to measure soil water content accurately

Wen

Liu

Horton

et al. 2018

European J Soil Science

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Summary To reduce the possibility of probe deflections, conventional thermo‐time domain reflectometry (T‐TDR) sensors have relatively short probe lengths (≤4 cm). However, short probes lead to large errors in TDR‐estimated soil water content (θv). In this study, two new 6‐cm‐long probe‐spacing‐correction T‐TDR (CT‐TDR) sensors were investigated. Compared with conventional 4‐cm‐long T‐TDR sensors, the 6‐cm‐long CT‐TDR sensors reduced errors in TDR‐estimated θv. Errors in heat pulse (HP)‐estimated θv because of probe deflections were reduced when linear or nonlinear probe‐spacing‐correction algorithms were implemented. The 6‐cm‐long CT‐TDR sensors provided more accurate θv estimations than do the conventional 4‐cm‐long T‐TDR sensors. Highlights Short thermo‐TDR sensor has shortcomings in determining soil water content. Changes in thermo‐TDR probe spacing caused by deflections can be determined in situ. Correcting changed thermo‐TDR probe spacing determined soil water content accurately. The 6‐cm‐long thermo‐TDR sensors determined soil water content more accurately than 4‐cm‐long sensors.

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Tangent Line/Second‐Order Bounded Mean Oscillation Waveform Analysis for Short TDR Probe

Cited by 17 publications

References 18 publications

Development and Application of the Heat Pulse Method for Soil Physical Measurements

Development and Application of the Heat Pulse Method for Soil Physical Measurements

An Improved Thermo‐TDR Technique for Monitoring Soil Thermal Properties, Water Content, Bulk Density, and Porosity

An in situ probe‐spacing‐correction thermo‐TDR sensor to measure soil water content accurately

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