A novel front-end for impedance spectroscopy

A novel method for calculating unknown impedances is presented. In contrast to synchronous detection (SD), which provides the real and imaginary components, the magnitude and phase of the impedance are calculated. Non-accurate generation of the required in-phase and quadrature signals required in SD and mismatches between the channels generate large errors. The proposed method does not require such signals. The measured potential across the sensor is rectified and then low-pass filtered to obtain the magnitude. The phase is calculated by two comparators followed by an XOR gate. A prototype of the system was built using discrete components and proof of concept measurements were carried out using resistors and capacitors of known values.