| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface electrometer which has a simple constitution and can reduce the variation of the measured surface potential value of a charged body caused by the variation of the distances between the charged body and detection electrodes. SOLUTION: Amplifier circuits 4 and 5 respectively amplify potential signals induced in a detection electrode 1, which is a fixed electrode and another detection electrode 2 which is an oscillating electrode. A detection circuit 6 detects a output signal Vb of the amplifier circuit 5. A subtraction circuit 7 outputs the signal of the level Vs, corresponding to the surface potential of a charged body by subtracting an output level Va of the amplifier circuit 4 from an output level Vc of the detection circuit 6. Since the influence of distance variation appears in both the electrodes 1 and 2, the influence can be eliminated, when the output level Va is subtracted from the output level Vc. |
