An Arduino-based EIS with a logarithmic amplifier for corrosion monitoring

Electrochemical Impedance Spectroscopy (EIS) is an interesting non-invasive technique to study the corrosion layer of metallic artifacts as well as to test the integrity of protective coatings, however commercial EIS systems are rather expensive devices. This paper describes an extremely low cost realization of an EIS system that is based on a simple commercial Arduino Board whose cost is below 50$. The instrument is able to perform impedance measurements in the range 1 kΩ to 1 GΩ, thanks to a specifically designed front end based on a logarithmic amplifier, and in the frequency range of 0.01 Hz to 100 kHz. The instrument can work as a stand-alone device or connected to a PC. The required current is of about 100 mA, thus, the USB port of a common laptop can power the instrument for several hours without external supply. It is also possible to employ several instruments at the same time for a massive parallel measurement campaign with a negligible cost. The instrument accuracy is of about 2% for impedances in the range of 1 kΩ to 100 MΩ, with uncertainty on the phase of about 2°.