Patent ID: 7109698

Claim:
An electric-field meter f or 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 on the housing and selectively exposed to the electric field; a shield assembly 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 one of the shield assembly and 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 one of the shield assembly and the electrode assembly and providing a position detection signal indicative of the position of one of the shield assembly and the electrode assembly; a charge measurement circuit having an input 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; means for determining an average leakage current at the input of the charge measurement circuit; and means for generating a compensation current generally equal to and opposite in polarity to the determined average leakage current at the input of the charge measurement circuit, wherein the compensation current is supplied to the input of the charge measurement circuit.