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Dielectric loss and calibration of the Hydra Probe water sensor

M. S. Seyfried, L. E. Grant, E. Du and K. Humes
Dielectric loss and calibration of the Hydra Probe water sensor (in Soil water sensing, Steven R. Evett (editor) and G. W. Parkin (editor))
Vadose Zone Journal (November 2005) 4 (4): 1070-1079

Abstract

Widespread interest in soil water content (theta , m (super 3) m (super -3) ) information for both management and research has led to the development of a variety of soil water content sensors. In most cases, critical issues related to sensor calibration and accuracy have received little independent study. We investigated the performance of the Hydra Probe soil water sensor with the following objectives: (i) quantify the inter-sensor variability, (ii) evaluate the applicability of data from two commonly used calibration methods, and (iii) develop and test two multi-soil calibration equations, one general, "default" calibration equation and a second calibration that incorporates the effects of soil properties. The largest deviation in the real component of the relative dielectric permittivity (epsilon ' (sub r) ) determined with the Hydra Probe using 30 sensors in ethanol corresponded to a water content deviation of about 0.012 m (super 3) m (super -3) , indicating that a single calibration could be generally applied. In layered (wet and dry) media, epsilon ' (sub r) determined with the Hydra Probe was different from that in uniform media with the same water content. In uniform media, theta was a linear function of epsilon ' (sub r) . We used this functional relationship to describe individual soil calibrations and the multi-soil calibrations. Individual soil calibrations varied independently of clay content but were correlated with dielectric loss. When applied to the 19-soil test data set, the general calibration outperformed manufacturer-supplied calibrations. The average theta difference, evaluated between epsilon ' (sub r) = 4 and epsilon ' (sub r) = 36, was 0.019 m (super 3) m (super -3) for the general equation and 0.013 m (super 3) m (super -3) for the loss-corrected equation.


ISSN: 1539-1663
Serial Title: Vadose Zone Journal
Serial Volume: 4
Serial Issue: 4
Title: Dielectric loss and calibration of the Hydra Probe water sensor
Title: Soil water sensing
Author(s): Seyfried, M. S.Grant, L. E.Du, E.Humes, K.
Author(s): Evett, Steven R.editor
Author(s): Parkin, G. W.editor
Affiliation: U. S. Department of Agriculture, Agricultural Research Service, Boise, ID, United States
Affiliation: U. S. Department of Agriculture, Soil and Water Management Research Unit, Bushland, TX, United States
Pages: 1070-1079
Published: 200511
Text Language: English
Publisher: Soil Science Society of America, Madison, WI, United States
References: 35
Accession Number: 2006-007635
Categories: SoilsApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N31°15'00" - N37°00'00", W115°00'00" - W109°00'00"
N30°19'60" - N35°00'00", W85°34'60" - W80°45'00"
N42°00'00" - N49°00'00", W117°15'00" - W111°04'60"
N40°25'00" - N43°30'00", W96°34'60" - W90°10'00"
N30°15'00" - N35°00'00", W91°40'00" - W88°04'60"
N33°34'60" - N37°00'00", W103°00'00" - W94°25'00"
N42°45'00" - N45°00'00", W73°25'00" - W71°30'00"
Secondary Affiliation: University of Guelph, CAN, CanadaBoise State University, USA, United StatesUniversity of Idaho, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 200603
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