Abstract— Impedance spectroscopy (IS) involves measurements
of impedance amplitudes, which often span more than six/seven
decades. Currently available IS systems employ sophisticate
front-ends to cope with this wide impedance range and, consequently, the cost of the measuring instrument greatly increases.
This paper describes an alternative low-cost solution, which
is based on a logarithmic front-end and on an off-the-shelf
microcontroller board. Using these components, the cost remains
below $100, while still having the capability of measuring over a
frequency range of 0.01 Hz–100 kHz and for impedance values
in the range of 100 –10 G. The overall uncertainty remains
below 5% of amplitude and few degrees of phase. The proposed
system is, therefore, suitable for electrochemical impedance
spectroscopy applications, as well as for bioelectrical impedance
analysis.
Index Terms— Bioelectrical impedance analysis (BIA), corrosion assessment, electrochemical impedance spectroscopy (EIS),
impedance spectroscopy (IS), logarithmic amplifiers.
I. INTRODUCTION
IMPEDANCE spectroscopy (IS) is a technique employed to obtain information on the physicochemical properties of
many different systems and IS measurements are generally
divided in two categories: 1) electrochemical IS (EIS), mainly
employed for the analysis of the ionic conduction inside the
material and 2) all other impedance measurements performed
on dielectric systems and on materials with predominant
electronic conduction. In all cases, IS analyses are performed
by measuring amplitude and phase of the impedance of an
object surface. All the measurements are performed using a
small voltage stimulus, usually limited to 10–100 mV to avoid
perturbing the systems under measurement, which are often
nonlinear, while the frequency range is selected according to
the phenomena that should be investigated. The IS measurements can be performed in a frequency range, which may
extend over nine orders of magnitude or more: from 10 mHz
to obtain a good resolution of interfacial processes, up to
10 MHz needed to collect the bulk response of the material
under measurement.
In the medical field, IS applied to the body, usually referred
to as bioelectrical impedance analysis (BIA) permits to