Atmel AVR Controlled Digital Capacitance Meter

The integration method was used to build this capacitance meter where it measures the time it takes a capacitor to charge to calculate the capacitance.

An Atmel AVR MCU is utilized in this circuit while requiring some calibration. The capacitance value can be measured easily by this capacitance meter but with some measurements method. The integration method brings an advantage that the result obtained can be as digital data directly since its basis of measurement of time, accurate analog circuit is not required and the microcontroller is used for easy calibration. This makes the integration method suitable for hand-built capacitance meter.

A voltage comparator, counter, and some glue logics are needed to measure a charge time. The system is easily realized by using an AT90S2313 microcontroller. The divider registers generates the threshold voltage while a DC-DC converter powered from a 1.5V AA cell generates the supply voltage. Although the switching power supply is not suitable for measurement circuit, it is not affected by ripple voltage due to the two applied ripple filters. The capacitance meter does not have any trimmer pot and it performs the calibration by reading the reference capacitor during operation.

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