A DIY LC meter built around the Franklin oscillator circuit, a historically obscure design from the 1920s Marconi era. The meter uses an Arduino to count the resonant frequency of an LC tank circuit, then measures the frequency shift when an unknown capacitor or inductor is added. By comparing frequency differences rather than absolute values, parasitic effects are minimized. Calibration uses a known reference capacitor, implemented either via relay or manual switch. The design achieved inductance measurements as low as 0.1 µH.
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