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A Small‐Scale Matric Potential Sensor Based on Time Domain Reflectometry
Author(s) -
Persson Magnus,
Wraith Jon M.,
Dahlin Torleif
Publication year - 2006
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2005.0209n
Subject(s) - reflectometry , gypsum , loam , soil science , water potential , environmental science , time domain , materials science , root mean square , soil water , geotechnical engineering , mineralogy , geology , composite material , engineering , electrical engineering , computer science , computer vision
Measurements of soil matric potential (ψ) are needed in many soil science applications. In the present study, a small matric potential sensor having a length of 30 mm and a diameter of 9.6 mm was developed. The sensor consists of two coils made of lacquer‐coated copper wires embedded in gypsum. The dielectric constant of the gypsum ( K gypsum ) was measured with time domain reflectometry (TDR). The gypsum probes were tested in a sandy loam soil using a pressure extractor to obtain the relationship between K gypsum and ψ, allowing inference of the soil ψ in equilibrium with the sensor. It was shown that the gypsum probe could give ψ estimates with a root mean square error (RMSE) of around 50 kPa in the range of −20 to −1500 kPa. Most of the sensitivity of the sensor was in the −50‐ to −1000‐kPa range.