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