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.<<ETX>>