Abstract: A device for sensing changes in the permittivity of a sample of a monitored medium is disclosed. The monitored medium is exposed to an environment having one or more elements. The device includes an LC oscillator circuit and an output circuit coupled thereto. The LC circuit contains an inductance element and a capacitance element and has a resonance frequency which is dependent upon the permittivity of the sample. The capacitance element includes first and second conductive elements surrounded by an insulating dielectric material so that the first and second conductive elements are prevented from being exposed to one or more elements of the environment of the sample. The output circuit is adapted to output a signal representative of the permittivity of the sample. A method of determining changes in the permittivity of a sample of a medium is also disclosed.