Patent ID: 7439746

Claim:
An electrostatic voltmeter, comprising: an input sensing terminal; a first operational amplifier (“amplifier A 1 ”) having a non-inverting input (“non-inverting input A 1 ”), an inverting input (“inverting input A 1 ”) and an output (“output Al”), the non-inverting input A 1 being electrically connected to the input sensing terminal, and the inverting input A 1 being electrically connected to the output A 1 to create a voltage follower; a second operational amplifier (“amplifier A 2 ”) having a non-inverting input (“non-inverting input A 2 ”), an inverting input (“inverting input A 2 ”) and an output (“output A 2 ”), the inverting input A 2 being electrically connected to the output Al, and being electrically connected via a capacitor to the output A 2 ; a first reference voltage terminal electrically connected to the non-inverting input A 2 ; a low reference voltage terminal electrically connected to the output A 2 ; a voltage indicator, electrically connected between the low reference voltage terminal and the first reference voltage terminal; an inverting operational amplifier (“amplifier A 4 ”) having an inverting input (“inverting input A 4 ”), a non-inverting input (“non-inverting input A 4 ”) and an output (“output A 4 ”), the inverting input A 4 being electrically connected to the low reference voltage terminal, and the non-inverting input A 4 being electrically connected to the first reference voltage terminal; and a first voltage source (“source V 1 ”) and a second voltage source (“source V 2 ”), source V 1 and source V 2 being arranged in series and the first reference voltage terminal being electrically located between source V 1 and source V 2 ; and a third voltage source (“source V 3 ”) and a fourth voltage source (“source V 4 ”), wherein source V 3 and source V 4 being arranged in series and the first reference voltage terminal being electrically located between source V 3 and source V 4 .