Patent ID: 7256572

Claim:
An electric-field meter for measuring at least one of a magnitude and polarity of an electric field, comprising: a housing at least partially constructed of a conductive material, the housing defining a retaining space; an electrode assembly maintained in a stationary position on the housing and selectively exposed to the electric field; a shield assembly maintained at the ground reference potential and movable with respect to the electrode assembly through a predetermined path for alternately covering and exposing the electrode assembly to the electric field; a movement assembly having a source of motive force and a linkage operably connected to the shield assembly for moving the shield assembly with respect to the electrode assembly for alternately covering and exposing the electrode assembly to the electric field; a position detection assembly for monitoring the position of at least a portion of the shield assembly and providing a shield position detection signal indicative of the position of the shield assembly; a charge measurement circuit receiving charge on the electrode assembly, the charge measurement circuit providing a charge detection signal indicative of the charge induced on the electrode assembly as the electrode assembly is selectively exposed to the electric field; and means for mechanically adjusting an effective aperture to vary the exposure of the electrode assembly to the electric field.