A moisture content sensor for measuring the moisture content of a medium. The sensor includes a probe that injects an electrical signal into the medium. Complex impedance circuitry located between the probe and the electrical signal source allows sensing electronics to generate a signal that represents the moisture content within the medium based on changes in the permittivity of the medium. The complex impedance circuitry minimizes the influence of temperature and conductivity of the medium on the sensed signal. The sensing electronics may be adjusted to optimize the sensor for varying medium conditions and to vary the linearity of the response curve based on volumetric water content of the medium.