| 摘要 |
PROBLEM TO BE SOLVED: To measure the capacity value of a capacity to be measured by removing the influence of a parasitic capacity in a shielded box or its change. SOLUTION: The infinitesimal capacity measuring system comprises a prober 1, a signal line brought at one end into contact with a sample to be measured, a shielding wire for enclosing the line, and a capacity measuring circuit 6. The circuit 6 has an inverting input terminal connected to the other end of the line and a non-inverting input terminal connected to the shielding wire in such a manner that the inverting terminal and the non-inverting terminal is imaginarily short-circuited therebetween. The circuit 6 further has an operational amplifier 61 for outputting a signal having a value corresponding to an electrostatic capacity of the sample to be measured when an AC signal is applied to the non-inverting terminal. A conductive part of the box 11, a conductive part of a stand 13, a surface of the sample brought into contact with the stand 13 and the shielded wire are set to the same potential.
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