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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #205014

Title: A Partial Cylindrical Thermo-Time Domain Reflectometry Sensor


Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2007
Publication Date: 4/8/2008
Citation: Olmanson, O.K., Ochsner, T.E. 2008. A partial cylindrical thermo-time domain reflectometry sensor. Soil Science Society of America Journal. 72:571-577.

Interpretive Summary: Thermo-time domain reflectometry (T-TDR) sensors are useful tools in soil science research. They can be used to measure numerous important soil properties like water content, density, and thermal properties. This paper reports the development of a new design for T-TDR sensors which overcomes some of the limitations of the previous designs. The new sensor is larger and more robust, and its accuracy is not affected by deflection, a significant problem with prior designs. This new sensor design will benefit scientists and engineers whose work requires the non-destructive measurement of soil physical properties.

Technical Abstract: Thermo-time domain reflectometry (T-TDR) sensors are multi-functional devices that can be used to measure soil thermal properties and water content. These sensors can also be used to obtain indirect estimates of bulk density, air-filled porosity and percent saturation. However, the small size of the conventional three needle T-TDR sensor may limit its accuracy, precision, and durability. In this study we changed the size and geometry of this sensor to improve accuracy and precision and to better withstand the stress of field use. The new design uses opposing curved blades with a single central needle. The new sensor was built, calibrated, and validated in the lab. The results indicate that the new sensor was capable of estimating soil water content and a number of soil thermal properties. Qualitative assessment indicated that this type of sensor may be less prone to distortion during field use.