Thermo-TDR probes can function both as a regular time domain reflectometry (TDR) probe, for measuring moisture and density, and a dual-heat probe for measuring thermal conductivity, thermal diffusivity, and volumetric heat capacity. The probe measurement sensitivity and accuracy are affected by probe length, diameter, and spacing. In this paper, two thermo-TDR probes were fabricated based on an improved design of a previous one. The two probes were first calibrated for measurement of dielectric constant and electrical conductivity using standard chemical solutions. Then, moisture, density, and thermal measurements were taken in custom designed compaction molds filled with ASTM fine-grade compacted sand using the thermo-TDR probes as well as KD2 probes. Calibrations are reported for the thermo-TDR probes measuring soil moisture, density, and thermal conductivity. The effect of sensor fabrication and sample preparation tests are evaluated. Recommendations are provided for using thermo-TDR probes for measuring in sand.
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