Apparatus for measuring voltages and currents using non-contacting sensors

A non-contacting system for measuring the AC voltage of a first frequency on conductive element comprising:

• sensor means for generating a first signal in response to the AC voltage of said conductive element, said sensor means including a conductive sensing electrode positioned so as to be spaced from and at least partially circumscribe said conductive element wherein said conductive sensing electrode is electrically coupled to said conductive element solely through a coupling capacitance therebetween;
• a calibration source for providing a calibration AC voltage at a locally determined frequency, said sensor means including means responsive to said calibration AC voltage for impressing a calibration voltage between said conductive sensing electrode and said conductive element;
• whereby a calibration response signal at said locally determined frequency is produced by said sensor means as a consequence of said impression of said calibration voltage, said calibration response signal being a function of said coupling capacitance;
• and
• calibration network means, operatively coupled to said sensor means, for adjusting said first signal by a gain factor determined in accordance with said calibration response signal in order to generate an output signal indicative of said AC voltage of said conductive element;
• said output signal being substantially independent of said coupling capacitance between said conductive element and said conductive sensing electrode.