BRS measuring devices, used in production

Fundamentals of Spectral Impedance

The impedance of an electrochemical cell, e.g. a battery, depends on the frequency and increases with decreasing frequency. The impedance has ohmic and capacitive / inductive components; it is therefore measured according to its amount and phase or – more common in electrochemistry – according to the active component and reactive component.

The frequency response is often represented in the form of a Nyquist plot: the abscissa shows the ohmic (active) component, the ordinate the capacitive (reactive) component. The frequency is a parameter and decreases to the right.

There are 3 areas, each of which represents a specific property of a cell:

  • The high frequencies (≈1kHz) show the influence of the electrolyte
  • The middle frequencies (100Hz … 10Hz) represent the electrodes
  • The low frequencies (1Hz … 0.1Hz) represent diffusion effects.

On the basis of the Nyquist plot, changes in the state can be inferred easily and clearly. 

The spectral impedance measurement is clearly displayed in the locus curve (Nyquist plot).

Video “Battery Test System” – easily explained in 3 minutes.