| 摘要 |
<p>An impedance meter capable of highly repeatable measurement by keeping the level (voltage level or current level) of the AC signal applied to a device under test (DUT) constant. An A/D converted voltage across the DUT or the feedback resistor R is provided to a microprocessor 40. The microprocessor 40 compares this level with an appropriate reference and feedbacks the result of said comparison to the level control circuit 20 (e.g. multiplying DAC). Because the feedback for the level control is done in a digital manner, it does not impair the analog stability of the measurement system. (If the level control were done with an analog feedback loop, such a level control feedback loop and the feedback loop consisting of high gain amplifier 20 and the feedback resistor R could interfere each other, resulting degradation of the stability of the system).</p> |
