The invention relates to a capacitive sensor system for measuring environmental parameters by activating a capacitive array and causing fringe electric fields to intersect the surrounding environment. An oscillator is coupled to the capacitive array and the frequency of oscillation depends upon the capacitance of the array, which represents an environmental parameter. The sensor is suitable for measuring resistivity and dielectric constant parameters in geophysical, environmental, hydro-geological and related applications. The conductors of the capacitive array can be arranged around a perimeter for use, for example, in a borehole or the conductors can be arranged in the same plane for use, for example, beneath a raft in shallow water. In the situation where the boreholes are fluid-filled, there are economic and technical advantages in using the metal plugs (normally used to seal the probe housings at each end), as the capacitive array in galvanic contact with the fluid.