Constant phase element

A constant phase element is an equivalent electrical circuit component that models the behaviour of a double layer, that is an imperfect capacitor.

The electrical impedance can be calculated:

$Z_{CPE}={\frac {1}{Q_{0}(\omega i)^{n}}}={\frac {1}{Q_{0}\omega ^{n}}}e^{-{\frac {\pi }{2}}ni}$

with Q₀ = 1/|Z| at ω = 1 rad/s

The constant phase is always -(90*n)°, with n from 0 to 1. The case n = 1 describes an ideal capacitor while the case n = 0 describes a pure resistor.