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A Partial Cylindrical Thermo-Time Domain Reflectometry Sensor

^a Dep. of Soil, Water, and Climate, Univ. of Minnesota, St. Paul, MN 55108
^b USDA-ARS, Soil and Water Management Research Unit, St. Paul, MN 55108

View larger version (14K): [in this window] [in a new window]   Fig. 1. The partial cylindrical thermo-time domain reflectometry sensor.

View larger version (13K): [in this window] [in a new window]   Fig. 2. Relative maximum temperature rise vs. relative deflection of the temperature sensing needle from initial position for dual-probe (solid line) and partial cylindrical heat pulse sensors (dashed lines). The inset denotes heater position and radial orientation of transects for the partial cylindrical sensor. The heater is positioned at –1 for the two-needle sensor.

View larger version (8K): [in this window] [in a new window]   Fig. 3. Measured temperature curve for the partial cylindrical sensor in water and theoretical model (Eq. [A3]). The model predictions are based on independent reference values for the thermal properties of water (Table 2) and sensor parameters calibrated in saturated glass beads.

View larger version (9K): [in this window] [in a new window]   Fig. 4. Measured vs. theoretical heat capacity for the partial cylindrical sensor in Ida silt loam.

View larger version (9K): [in this window] [in a new window]   Fig. 5. Thermal conductivity measurements from the partial cylindrical sensor in Ida silt loam vs. measured air-filled porosity. Thermal conductivity data for a similar soil from Ochsner et al. (2001a) are shown for comparison.

View larger version (9K): [in this window] [in a new window]   Fig. 6. Sensor estimates vs. measured values for volume fractions of water, solids, and air from laboratory packing experiment with Ida silt loam.

View larger version (18K): [in this window] [in a new window]   Fig. 7. Measured heat pulse curves in soil, saturated glass beads, and agar-stabilized water showing discrepancies between the upper and lower thermistors.