I am using the design below for a capacitance meter project:
simulate this circuit – Schematic created using CircuitLab
The charge/discharge waveform is relatively stable, so I feel that there's a fairly simple way to calculate capacitance based on measured Vmin, Vmax, ∆t, and resistors R1 and/or R2. What's the approach to calculating capacitance based on graph data?
As you can find in the 555 datasheet: https://www.ti.com/lit/ds/symlink/ne555.pdf?ts=1753827035701 The period is T = 0.693 × ( R1 + 2R2 ) × C. You can measure the period with an oscilloscope on pin 3 (output) the upper chart in your question, and inverting the formula above to derive C. Resistor are a little low, maybe R1=2K and R2=50K is better to prevent too much current in discharge phase. Choose R2>>R1 to have a duty cycle closed to 50%. Not strictly necessary, but maybe easyer to read.
