If ZSIMPWIN is too outdated, use:

| Software | Pros | |----------|------| | Python Control Library | Free, scriptable, modern | | Octave | Open-source Matlab alternative | | Jupyter + control package | Best for teaching/recording | | Simulink | Industry standard (paid) |

Tools → Kramers-Kronig
Checks if your data is physically consistent (causal, linear, stable). Run before fitting.

In the parameters table, enter starting values:

| Parameter | Guess method | |-----------|---------------| | R (high frequency) | Z' at high freq (≈ 0.1–10 Ohm) | | R (charge transfer) | Diameter of semicircle | | C (double layer) | 1e-6 to 1e-4 F (depends on area) | | CPE exponent (n) | 0.8 if unsure | | Warburg (σ) | Slope of low-freq 45° line ÷ 10 |

Enable fitting: Check the Fit box for each parameter.
Set bounds: Use Lower and Upper columns (optional but prevents divergence).