Ultra high impedance voltmeter for electrostatic applications

A new kind of voltmeter suitable for electrostatic measurements is proposed. It features an extremely high input impedance (more than 3/spl middot/10/sup 16/ /spl Omega/) and very low input capacitance (less than 10/sup -16/ F). Such low input capacitance and high input resistance allow for contacting voltage measurements which transfers virtually no electric charge to/from the measured object. The voltmeter combines a voltage follower technique with a unique input zeroing and bias current cancellation circuit. It has been designed specifically for monitoring the voltage on electrostatic sensitive devices during their handling and processing.