There are several models accounting for the induced polarization phenomenon in terms of complex, frequency-dependent conductivity sigma or resistivity rho = 1/sigma. The most popular ones are the Cole-Cole conductivity and Pelton resistivity models. Each model includes four parameters: resistivity rho (or its inverse, conductivity sigma), chargeability m, relaxation time tau and frequency dependence c. Some authors argue that these models predict different relaxation times and are equivalent provided that this difference is accounted for in interpreting induced polarization data. We show that the discussion about the equivalence of the Cole-Cole conductivity and Pelton resistivity equations might arose from not taking into consideration the difference between the relaxation time as a model parameter, and that observed experimentally. We also show that, when comparing models as such, there is no reason to talk about different relaxation times. The equivalence of conductivity and resistivity equations manifests itself in that both, with allowance made for the measurement circuit, predict the same experimental data.
