LC meter based on Franclin oscillator by Arduino nano

The Franclin oscillator is composed of the LC resonator and the phase inverting amplifier. The digital capability could lead LC meter which was calculating L or C value from the basic capacitor's capacitance by solving correlated equations from the oscillation frequency number.

[To compose the Franclin oscillator and MPU ] A certain Eastern European electronics engineer found this idea in along 1990’s. After then the Australian Ham magazine had picked it up as a technical article. At that time AADE( On his WEB he wrote that he had been a Boeing engineer.) had already introduced this circuit, produced, and sold it as a product for HAMs. In Japan, the Strawberry-Linux company and CYTEX company had developed a clone and sold those for HAMs.

Below is an explanation of how to calculate the capacitance or the inductance.

// a. To oscillate and measure the frequency of F1.

// b. To add the standard capacitor paralleled and get the frequency of F2.

// c. There is two-equation for the circuit.

F1＝1/2πsqrt(C1L1), F2=1/2πsqrt((C1+C2)L1).

// d. F1, F2, C2 are the valid value. We could draw C1 and L1 by the mathematical process.

// e. When you put L2 serially and get F31, you shall draw L2 value out of the equation. Also C3 by F32. F31=1/2πsqrt(C1*(L1+L2)), F32=1/2πsqrt((C1+C3)*L1).

I use 74HCU04 inverter IC for the Franclin oscillator. For the sake of switching the standard capacitor, I had adopted the relay. If you use semiconductor switching, accuracy may decline. The two-pole two circuit switch is necessary for LC change. I use i2c interfacing LCD for display.

There are the circuit diagrams below site.

https://cdn-ak.f.st-hatena.com/images/fotolife/n/nobcha23/20200714/20200714202214.jpg https://cdn-ak.f.st-hatena.com/images/fotolife/n/nobcha23/20200726/20200726214857.jpg