| 摘要 |
PURPOSE:To enable accurate detection of potential of an object to be measured by detecting a reference voltage with one of two potential sensors provided in the same case to determine the ratio between outputs of sensors. CONSTITUTION:When the surface potential of an object to be measured as developed with the application of the surface potential VD to a metal plate 11 is represented by Vs, an AC output voltage generated in an electrode 3 is given by Vs=AVs while an AC output voltage generated in an electrode 13 by Vo=BVo (where, A and B are proportion constants). Then, when the output voltage varies due to variation in external environment or the like, the voltage vs' and vo' turn to the vs'=ACV and vo'=BCVo (C is variation factor). When the ratios of voltages generated in the electrodes 3 and 13 between those before and after the respective changes are represented by R and R', R=vs/vo=AVs/BVo and R' vs'/vo'=ACVs/BCVo=AVs/BVo=R and hence, R is always given by R=DVs, where D=A/(BVo) (D is constant) regardless of environmental conditions. Thus, the surface potential of the object being measured can be detected accurately free from changes by determining the voltage ratios of the electrodes 3 and 13. |
