| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of drifts in the output voltage of an impedance/voltage converter corresponding to the value of an impedance to be measured due to environmental changes, the heat generated from the converter itself, and so on. SOLUTION: Immediately after measurement is started, the impedance/voltage converter connects a dummy impedance Zd between the inverted input terminal and output terminal of an operational amplifier 1 by controlling a switch circuit 9 and causes a sample-and-hold circuit 10 to hold the DC voltage value corresponding to the dummy impedance Zd from an AC/DC conversion circuit 2. Then, the converter connects an impedance Zx to be measured between the inverted input terminal and output terminal of the amplifier 1 by switching the switch circuit 9 and, at the same time, causes a subtraction circuit 11 to subtract the voltage held by the 10 from the DC voltage corresponding to the impedance Zx from the conversion circuit 2. Thereby, an output in which drift components are offset can be obtained.
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