This command performs the Kramers-Kronig Transform (KKT) on your experimental data and displays the result as a Fit on the Bode and Nyquist charts. It also adds a Kramers-Kronig results tab. This tab displays a grid containing the "Goodness of Fit" and a plot of the relative errors (ΔZ/Z ) for the real and imaginary parts of the experimental data. The calculation is done following the method of Boukamp(1).

The KKT of your data calculates the spectrum of a Linear, Stable, and Causal circuit. No model is assumed. The real part of your experimental data is used to calculate the imaginary part of a Linear, Stable, and Causal circuit. Likewise, the imaginary portion of your experimental data is used to calculate the real part of a Linear, Stable, and Causal circuit. The KKT is shown on the Bode and Nyquist plots. If the KKT and the experimental data do not agree, then the sample may exhibit non-linearity, instability, or the influence of unknown variables (non-causal).

References:

(1) "A Linear Kronig-Kramers Transform Test for Immittance Data Validation," B.A. Boukamp, *J. Electrochem. Soc.*, **142** (1995), 1885–1894.