Calibration of an AC Zero Potential Circuit for Two-Dimensional Impedimetric Sensor Matrices

Abstract

The alternating current zero potential circuit (AC-ZPC) has been recently proposed for two-dimensional resistive sensor matrices, where each matrix row is driven by an AC signal at an individual frequency and every column is read separately. The AC-ZPC method enables the simultaneous measurement of all sensors in the matrix and is insensitive to DC offset voltages of amplifiers. This work aims to investigate the feasibility of the AC-ZPC method for matrices of impedimetric sensors and to propose a calibration approach for suppressing the measurement deviations caused by row interface impedances. The feasibility of the AC-ZPC measurement method for the impedimetric sensor matrices and the proposed calibration approach have been proved by both simulation and implementation results. Based on the commercial impedance measurement circuit AD5933, a prototype has been realized. It achieves a measurement deviation below 1% in the range from 1.9 $\text{k}\Omega \vert \vert 361.7$ pF to 15.9 k $\Omega \vert \vert 102.0$ pF.