| 摘要 |
PURPOSE:To measure high resistance at a high speed while reducing the nfluence of a low-frequency noise such as a hum noise by flowing currents from a positive and a negative constant current circuit which flows output currents equal in absolute value and has symmetrical circuit constitutions to resistance to be measured. CONSTITUTION:Operational amplifiers 2g-2i and precise resistances R10 and R11, and R1-R3 constitute the positive constant current power circuit, and operational amplifiers 2j-2l and precise resistances R10 and R11, and R1-R3 constitute the negative constant current power circuit. Further, the power source balancing circuit composed of an operational amplifier 2m and the precise resistance R10 keeps the balance between the output currents of the positive and negative constant current power sources, and measurement ranges are changed with a changeover switch 6. The current Ip from the positive constant current powerl circuit flows through a resistance Rx to be measured and flows in the negative constant current power source as IN, and the voltage developed across the resistance Rx to be measured is outputted through the differential amplifier circuit consisting of operational amplifiers 2b-2d and precise resistances R5-R8.
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