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High resolution lightweight capacitance meter on PIC

Many capacitance meters limits their resolution to 3 or 4 digits while this one reaches 7 digits. What does it mean? This means that you can measure capacitance more precisely especially when talking about very small capacitors in pF range. Device is built around PIC16F628 microcontroller which also provides its internal comparator for oscillator.

Using PIC’s internal comparator makes cap meter very lightweight on schematic. Whole magic happens in comparator circuit where tested cap along with known resistor generates a waveform. Comparator is set to capture high and low signal values at 1/3VDD and 2/3VDD while microcontroller timer counts waveform period. Knowing period it is easy to calculate capacitance value. Cap meter also has a zeroing and calibration functions that helps reaching better precision.

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