The authors have developed a Cone Penetration Testing (CPT) probe which measure both the resistivity and the dielectric constant of the soil. This method is innovative because the water relaxation effects due to interfacial polarization are greatly reduced. This effect has plagued previous researchers and resulted in inaccurate measurenets of the soil dielectric constant. The design of our sensors consists of our concentric rings spaced along the penetration rod with insulators in between. The outer two rings determine the soil resistivity; the inner two rings measure the capacitance using a modified Clapp highfrequency transistor oscillator operating at 100 Mhz. The CPT measured dielectric constant can be used to calculate the soil volumetric mositure content by directly calibrating to the soil of interest. A more general equation, such as Topp;s Universal Equation, can determine the volumetric moisture content.
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