Galvanostatic EIS (GEIS)

Electrochemical Impedance Spectroscopy (EIS) is an electrochemical technique that measures the impedance of a system as a function of AC current frequency. EIS enables the separation of different component influences, including contributions from electron transfer resistance, double layer capacitance, and other electrochemical processes.

GEIS applies a galvanostatic sinusoidal excitation signal and analyzes the resulting potential response from the device under test (DUT). The density parameter determines the number of measurement points within a specified frequency range. Averaging multiple sine waves reduces noise and non-systematic interference, although this increases the total measurement time.

Galvanostatic EIS is ideal for devices under test (DUT) with low impedances, such as fuel cells, electrolysis cells, batteries, and supercapacitors. High capacitance devices exhibit very long relaxation times. A drifting open circuit voltage (OCV) can cause very high equalizing currents in low impedance devices.

Parameter Description

Parameter	Name	Description	Unit
I dc bias	DC bias current	DC bias current for defining the operating point of the object set to zero for state of charge	A
I amplitude	amplitude	AC current peak amplitude sine wave stimulation is from bias-amplitude to bias+amplitude	A
f start	start frequency	starting frequency of the impedance spectrum useful to check system stability by forward and backward scan	Hz
f max	maximum frequency	upper frequency limit of the impedance spectrum	Hz
f min	minimum frequency	lower frequency limit of the impedance spectrum most effect on EIS runtime	Hz
t meas	minimum measurement time	minimum recording time for each frequency step allow more averages at higher frequencies	s
N waves	minimum averages	minimum number of sine waves for each frequency step more averages for higher SNR
Density >66Hz	density above 66 Hz	number of frequency steps per decade between 66 Hz and f max frequency steps are logarithmic equidistant
Density at f min	density at f min	number of frequency steps per decade at f min logarithmic linear density from f min to 66 Hz

A Start Phase Galvanostatic can be enabled or disabled before the method is executed.

Measurement Result

The measurement results can be displayed as either Nyquist or Bode plots. To evaluate the spectra, the measurement data is fitted to a representative equivalent circuit model of the DUT. This approach enables the determination of detailed individual parameters for each equivalent circuit element.

Custom Experiment Builder

This experiment is a combination of the following blocks:

• Ramp - Current Voltage Curve

• Electrochemical Impedance Spectroscopy