New designs of ´field mill´ type fieldmeters not requiring earthing of rotating chopper

Two designs for the field mill electrostatic fieldmeter that avoid the need for earthing the rotating chopper are described. The first uses a second fieldmeter section to compensate for the voltage on the rotor; the second uses a constant-capacitance rotor with capacitive pickup of the modulated field signal at the rotor. These approaches enable long-term continuous and fast response electric field measurements to be made with good zero stability and high sensitivity.<>