Low-Cost Impedance Spectroscopy System Based on a Logarithmic Amplifier

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 Ω-10 GQ. 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.