Duty cycle based digital capacitance meter

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Abstract
A novel digital capacitance meter based on varying the duty cycle of a waveform is presented. The main features of the meter are its low component count, its accuracy, resolution and tolerance to wide variations in the supply voltage and the clock frequency. The capacitance of the unknown capacitor is directly related to the duty cycle of the rectangular wave generated during the measurement process. Unlike various earlier methods, the choice of the component values is neither specific nor critical over a wide range. The output of the analogue part may be averaged and connected to an existing analogue/digital voltmeter to measure the capacitance directly. In such a case, however, a regulated power supply will become necessary. A set of readings, taken with the proposed meter and a commercial meter, is given for the purpose of comparison.

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