Magnetic Resonance Amplifier 5: Dual Piezos Increased Capacitance

Please watch the previous vids first, for background info and schematic.
Here I just put two of the Piezo elements in parallel, increasing the measured capacitance to 71.2 nF.

This has the predicted effect on the resonant frequency of the arrangement, once again demonstrating that the Piezo speaker elements, wired in series with the primary coil, act just like capacitors as far as the series LC tank circuit is concerned.

There is still a consistent about 5 percent error in the measured value compared to the calculated one. I think this is due to the extra stray inductances and capacitances in the circuit that I’m not including in the calculation, as well as the fact that I’m probably not hitting the frequency exactly with the coarse tuning of my FG knob and eyeball readings of the scopetrace amplitudes. I trust the frequency reading from the Philips counter for high accuracy, but I can’t read the scopetraces that well by eye alone.

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