A voltage sensor includes an insulator with mutually insulated electrodes embedded therein. The electrodes are coaxial and cylindrical and overlap axially along part of their lengths. They are mutually staggered and control the surfaces of electric equipotential such that there is a substantially homogeneous electric field outside the insulator and a substantially homogeneous but higher field within a sensing cavity within the insulator. A field sensor is arranged within the sensing cavity to measure the field. This design allows for the production of compact voltage sensors for high voltage applications.