| 摘要 |
PROBLEM TO BE SOLVED: To measure accurately a voltage of a measuring object, while constituting a filter circuit inexpensively. SOLUTION: A device 1 for measuring the voltage V1 of the measuring object 4 includes a probe unit 2 having a variable capacity circuit 19 for changing a capacitance C1 with a capacity modulation frequency f2 which is double of a frequency f1 of a driving signal S2, for outputting a detection signal S3 having the same frequency as the capacity modulation frequency f2, wherein the amplitude is changed corresponding to a potential difference (V1-Vr) between the voltage V1 and a reference voltage Vr; an intermediate frequency conversion part FT for mixing a detection signal S3 with an locally oscillated signal S5 generated from a local oscillation circuit 23, and then filtering them, to thereby generate an intermediate frequency signal S7; a detection circuit 26 for generating an amplitude signal S8 showing an amplitude component of the detection signal S3 by detecting the intermediate frequency signal S7; and a voltage generation part 3b for generating the reference voltage Vr, applying it to the probe unit 2, and changing the reference voltage Vr so that the amplitude of the amplitude signal S8 is reduced. COPYRIGHT: (C)2008,JPO&INPIT
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