| 摘要 |
PURPOSE:To simplify the constitution of a vibration part, and also to improve its response property, by controlling the quantity of charge induced in an electrode by a rotation of a shutter, and varying a gate electric field of a field effect transistor. CONSTITUTION:When an object to be measured 9 is charged with electric charge 8, a counter electrode 2 whose pole opposes to this electric charge 8 is charged with electric charge opposite in polarity, through an opening 5 of a case 6. In this case, to a field effect transistor 1, a drain current corresponding to the magnitude of an electric field of the gate proportional to the quantity of electric charge flows. Subsequently, when the opening part 5 is covered with a shutter 3 driven by a driving motor 4, no electric charge is induced in the counter electrode since the shutter 3 is grounded, and to the field effect transistor 1, a drain current in a state that there is no electric field flows. A difference between both of them is fetched as a detecting signal. In this way, the constitution is simplified, and also its response property can be improved by increasing the rotational frequency of the motor 4. |
