Validation of a soil interface model to account for apparent aberrations in capacitive soil moisture sensors

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Title Validation of a soil interface model to account for apparent aberrations in capacitive soil moisture sensors
Author Johnson, Peter; Watling, Kym Marjorie; Thiel, David Victor; James, Daniel Arthur
Publication Title Proceedings of SPIE on CD-ROM: Microelectronics, MEMs and Nanotechnology
Editor Alex J. Hariz
Year Published 2006
Publisher SPIE (The International Society for Optical Engineering)
Abstract In this paper the operation of capacitive soil moisture sensors are modeled using an electrical circuit analogue. This model aims to predict the response of capacitive sensors for a variety of soil types, moistures, soil conductivity and sensor operating frequencies. The model is extensively validated under a variety of conditions for a variety of sensor circuits and measurement techniques. The deposition of a conducting film composed of clay-like soil material over the sensing surface of a soil moisture sensor is shown to be the cause of hysteresis when the sensor is operated at low frequencies (10KHz). As the frequency is increased (10MHz) the effect of the conducting film becomes insignificant. Surface chemistry analysis techniques were used to identify the soil deposits on the conducting film. This research is motivated by the design of a small disposable sensor printed on a flexible plastic substrate measuring soil moisture as a function of the number of point contacts terminating on the insulated sensor electrode. In controlled conditions the sensor exhibits a linear response across most of its range to water content changes, but in some soils the reading becomes "stuck" on a high reading and does not return to a lower reading until the soil has dried considerably.
Peer Reviewed Yes
Published Yes
Publisher URI http://spiedl.aip.org/dbt/dbt.jsp?KEY=PSISDG&Volume=6035&Issue=1
Alternative URI http://dx.doi.org/10.1117/12.639118
Conference name SPIE Symposium on Microelectronics, MEMS, and Nanotechnology
Location Brisbane
Date From 2005-12-12
Date To 2005-12-14
URI http://hdl.handle.net/10072/13409
Date Accessioned 2007-03-15
Date Available 2009-11-30T05:27:02Z
Language en_AU
Research Centre Centre for Wireless Monitoring and Applications
Faculty Faculty of Science, Environment, Engineering and Technology
Subject PRE2009-Biomedical Engineering
Publication Type Conference Publications (Full Written Paper - Refereed)
Publication Type Code e1

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