An EIS (Electrochemical Impedance Spectroscopy) Analyzer is a device that measures the response signal of a specific substance or electrode surface to an applied potential including a superimposed small sinusoidal potential waveform.
Just like a potentiostat an EIS Analyzer ensures that a potential is applied to a particular (liquid) substance, normally the applied signal of a potentiostat is stable, for EIS there is a small variation in the applied potential. This variation is a sinusoidal wave at an accurately controlled frequency and with a defined amplitude. For example, the PalmSens4 can apply sinusoidal waves with a frequency between 1 MHz and 10 μHz, the EmStat Pico can apply and measure sine waves up to 200 kHz.
EIS Analyzer measurements
The potential wave (Figure 1: blue) provides periodical potential differences between the electrode connected to the device and the object or (liquid) substance in contact with the electrode. This causes an electron current which also has sinusoidal waveform (Figure 1: green).
The EIS Analyzer measures the difference between the maximum current and the minimum current (i.e. the height or amplitude of the waves), but also the time difference between the potential and the current wave-forms. This allows the calculation of the electrical resistance (or better impedance) of the liquid or object. If multiple frequencies are tested, single components and effects that are responsible for this resistance, can be identified.
EIS Analyzer applications
An EIS analyzer is mainly used for Electrochemical Impedance Spectroscopy (EIS) to investigate the electrical resistance (measured in Ohm) of substances and objects. A few examples:
- How resilient is a paint coating? In other words, how will a coating behave over time? Without an EIS Analyzer a paint manufacturer could only reproduce the resilience of his coating in practice by long lasting exposure tests. However with an EIS analyzer it’s easy to predict the behavior for the next ten years with a short test. Read more about this on our Palmsens Corrosion website.
- How resilient is a concrete wall, does the steel in the wall not corrode too quickly? With an EIS analyzer you can predict in which type of concrete the steel corrodes faster.
- Measure the resistance of DNA of a particular cell. DNA always appears in double strands forming a helix. It is built up in such a way that the two strands of the pair match each other perfectly. If one strand is attached to an electrode, a coupling with the matching DNA strand is accompanied by a change in resistance. This can also be observed with an EIS Analyzer.
Benefits of an EIS Analyzer
The big advantage of an EIS Analyzer is that it allows the user to perform tests without having to destroy the object. This allows a manufacturer to test any of his products before they actually leave the factory without actually using or damaging them.
A second advantage is the predictive value of tests that are made with the use of an EIS Analyzer. An EIS Analyzer test (a so called frequency scan) also does not take much time at all, while testing for corrosive properties by salt spray tests takes a very long time.
EIS Analyzer sensors
Many materials can be analyzed with an EIS Analyzer. In corrosion research the corroding materials are connected directly to the EIS analyzer. This is similar in fuel cell or battery research. In analytical chemistry, a number of sensors were developed that only change their resistance in contact with specific substances. Also modern biosensors are investigated using impedance spectroscopy.
EIS Analyzer software
An EIS Analyzer is of no use without associated software. The PalmSens4 includes its own easy-to-use software, which allows you to run experiments smoothly and then use the equivalent circuit fitting to get the all required information out of your data. If you prefer you can also use your own or third party spreadsheet software for creating charts.
EIS Analyzer prices
EIS Analyzers can be pretty expensive, with the PalmSens4 instrument PalmSens managed to develop an EIS analyzer with outstanding specifications at a competitive price.