| 摘要 |
PURPOSE:To measure a surface potential accurately without any influence of an offset potential even if it is present by providing a surface potential measuring means and an electric discharging means, a measured value holding means and a correcting means, etc. CONSTITUTION:The surface potentiometer A and the electrostatic discharging means B, the measured value holding means C and a differential arithmetic means D as the correcting means, etc. are provided. When the surface of the potentiometer A is charged electrostatically to the plus polarity, an AC signal is induced across a detection resistance 5 an outputted as a surface potential from an output terminal 6a. In this case, the value of the AC signal induced across the resistance 5 is extremely small, so the device is covered with an external shield except at a part which faces a body alpha to be measured to prevent the influence of the outside and an internal shield 2 protects a measurement system from an internal noise. If the surface potential of the potentiometer A is not measured, the means B performs electrostatic discharging and the electrometer A takes a measurement, which is stored in the means C. the surface potential value is measured again and the means D subtracts the surface potential value stored in the means C. Consequently, the surface potential value including no offset potential is obtained. |
