Rapid response generating voltmeter

In a rapid-response generating voltmeter for measuring a high d-c voltage applied between first and second spaced-apart points,

• a. a first electrode adapted to operate at the potential of said first point,
• b. a second electrode spaced from said first electrode and comprising a first stator including a plurality of segments arranged in angularly-spaced relationship about a predetermined center and electrically connected together so as to be at the same potential as each other,
• c. a first capacitor connected between said first stator and said second point,
• d. a third electrode spaced from said first electrode, electrically insulated from said second electrode, and comprising a second stator including a plurality of segments arranged in angularly-spaced relationship about said center and positioned physically between the segments of said first stator, the segments of said second stator being electrically interconnected so as to be at the same potential as each other,
• e. a second capacitor connected between said second stator and said second point,
• f. capacitance-varying means for periodically varying substantially simultaneously in opposite senses the capacitance between said first electrode and said second electrode and the capacitance between said first electrode and said third electrode, said capacitance-varying means comprising a rotatable rotor having vanes normally at the potential of said second point located between said first electrode on one hand and the segments of said stators on the other hand, rotation of said rotor causing said vanes to gradually cover the segments of one stator with respect to said first electrode as said vanes gradually uncover the segments of the other stator with respect to said first electrode,
• g. said rotor vanes effectively completely covering the segments of said first stator at successive instants spaced in time by predetermined successive first intervals,
• h. first circuit means for sensing the voltage across said first capacitor and for developing during said first intervals a first intermediate signal varying in magnitude directly in accordance with:
• the voltage then present across said first capacitor minus a first error voltage substantially equal to the voltage across said first capacitor at the start of each of said first intervals,
• i. said rotor vanes effectively completely covering the segments of said second stator at successive instants spaced in time by predetermined successive second intervals,
• j. second circuit means for sensing the voltage across said second capacitor and for developing during said second intervals a second intermediate signal varying in magnitude directly in accordance with the voltage then present across said second capacitor minus an error voltage substantially equal to the voltage across said second capacitor at the start of each of said second intervals,
• k. and summing means for developing an output signal substantially proportional to the instantaneous sum of said first and second intermediate signals.