Topic 5 min read

Get the best EIS measurements, even with longer cables

Latest updated: June 5, 2024

Introduction

Due to its versatility, sensitivity, and non-destructive nature, Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for researchers and engineers. These advantages drive its increasing use across various industries and application fields such as materials science, corrosion studies, battery research, and electrochemical sensing.
In order to benefit from EIS, it is mandatory to pay close attention to the EIS measurement quality, which is directly linked to the overall setup design. Each part of the measurement chain can have a positive or negative influence on the quality of the measurements, including the chassis, channel boards, cell cables, and finally the accessories or interface elements (extension cables, battery holders, etc.).

Why are EIS contour plots relevant for your applications?

An EIS contour plot represents the accuracy level of an impedance measurement depending on the measured modulus (half Bode representation). This document allows you to determine the level of accuracy and frequency that can be used to perform your EIS measurement.

Depending on the required application, the areas of importance will differ:

  • High impedance values / top area
    • Corrosion (coating)
    • Materials studies (insulation components…)
  • Low impedance values / bottom area
    • Energy storage (battery, supercapacitor)
    • Energy conversion (fuel cell, electrolyzer, redox flow battery…)

 

Performance ready, under real laboratory conditions

BioLogic specifications (DC and EIS) are established using standard cell cables, which are 1.50 m and 1.75 m long for Essential and Premium range instruments, respectively.

These lengths are selected to match real world use, rather than to enhance the EIS specifications: these lengths are long enough to be suitable for standard laboratory use.

Note: most BioLogic accessories are designed and optimized for EIS measurements by allowing 4-point connections and limiting parasitic effects. This includes battery holders, high temperature extension cables and even material testing holders such as the CESH-e.

Why are BioLogic EIS accuracies preserved when using longer cables?

BioLogic cell cables are custom made for Biologic instruments and are optimized by design to minimize parasitic contributions. As an example, the internal cables that compose the cell cable are twisted in order to drastically minimize its parasitic inductance.

Essential range instruments

One of the advantages of Essential range instruments is that you can switch from one cable to another without having to shut down the instrument.

Parasitic effects are minimized by design but when switching to a longer cable, remaining effects that come from its extra length will not be considered and will affect high impedance measurement accuracies, whereas low impedance ones will not be affected.

As a solution, EC-Lab® post-processing compensation algorithm can be used. Only two initial measurements are required for that purpose. More information is available in this BioLogic learning center article: How to correct impedance measurements when using longer cables.

Premium range instruments, to go further

Premium range instrument cell cables are optimized by design similar to Essential range ones and are also paired with the channel board. This ensures that parasitic contributions are compensated through factory calibration up to the end of the cell cable, independent of the cable length. This is one of the added values of the Premium range instruments. The electrometer also allows precise calibration of low current ranges.

 

Conclusion

The accuracy of EIS measurements depends on a variety of factors but one component that is easily overlooked is the quality and length of the cables. BioLogic’s specially designed cables, in addition to factory calibration (Premium range instruments), can get rid of parasitic effects and get the best EIS measurements possible, without compromise.

Long cables extension cables EIS Contour plot Compensation parasitic effects

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