Menu: Logarithmic Kramers-Kronig Test

Analysis / Log-KK Check.
Generates a plot of residuals between modulus of impedance of calculated spectra based on Log-KK approach and modulus of impedance of experimental spectra.

Logarithmic Kramers-Kronig test procedure implemented in EIS Spectrum Analyser is based on approximations presented in [C.A.Schiller et al. Phys. Chem. Chem. Phys., 3 (2001) 374].

Logarithmic Kramers-Kronig test is based on interrelation between the logarithm of the impedance modulus Z and the phase angle shift φ for two-pole transfer functions. The validation of data can be performed through inspection of the relative residual plot between measured impedance modulus dependence on angular frequency and another one calculated from experimental dependence of phase shift on the frequency:

Normally, the lower the peak-to-peak amplitude in the residuals plots the better is quality of experimental impedance data.

Note 1: depending on properties of the dependence of the phase shift on frequency, the procedure sometimes can give large residuals even for near-to-perfect data due to limitations of Log-KK approach itself and a straight numerical integration/differentiation realized in this routine. Practically, residuals less than 2% may indicate ‘good’ quality of data. For more comprehensive validation of a spectrum, use this test in a combination with Linear Kramers-Kronig test

Note 2: Large peak-to-peak amplitude of the residuals may be caused by noisy data.