The thesis addresses the measurement of equivalent series resistance of a capacitor, using a frequency sweep ranging from 8 kHz to 10 MHz. To achieve a successful measurement, we designed and manufactured a printed circuit board containing the following functional blocks: a programmable sine wave generator, a voltage level adjuster, a Howland current source, and lastly an amplifier and peak detector.
The theory of operation is that the Howland current source drives alternating current to flow through the measured capacitor, resulting in the generation of an alternating voltage across the capacitor. For the purpose of adjusting the signal level for conversion in an analog-to-digital converter, the voltage is first amplified using noninverting amplifiers with an adjustable gain ranging between 2 and 2727. Subsequently, a peak detector is used to measure the peak voltage, which is then sampled by the built-in analog-to-digital converter of the microcontroller.
The measured results deviate somewhat from the true values due to the influence of the characteristics of the functional blocks, the influence of which has been characterized.
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