Patent ID: 6014028
Filing Date: 2000-01-11
Classification: G01R

Abstract:
A device for sensing a surface potential of an object, comprising:a sense electrode spaced a preselected distance from the object, electrically independent of the object;capacitance varying means for varying an electrostatic capacitance between the object and said sense electrode, comprising a chopper electrode disposed between the object and the sense electrode, a first vibrator configured to vibrate the sense electrode at a first frequency, and a second vibrator configured to vibrate the chopper electrode at a second frequency, to induce on said sense electrode, in association with the surface potential of the object, a potential having at least two different frequency components;potential detecting means for detecting said potential of said sense electrode induced in association with the surface potential of the object and varying along with the electrostatic capacitance;output detecting means for detecting said at least two frequency components in the potential detected by said potential detecting means; andsurface potential outputting means for determining the surface potential of said object based on the detected at least two frequency components and for outputting the determined surface potential of the object.