Development of a Portable Electrochemical Impedance Spectroscopy System for Bio-Detection

A portable electrochemical impedance spectroscopy (EIS) system has been developed based on FPGA for bio-detection. FPGA is a programmable signal processing chip, which cooperates with DAC module to generate the sweep excitation signal, controls ADC module to perform dual channel acquisition of voltage of a peripheral circuit, performs FFT and parameter calculation and transmits the result to PC for data processing. Based on FPGA internal programming, the system greatly reduces the size and achieves a single multi-frequency measurement, which enhances integration and portability of the system. The measurements of the electrical equivalent circuit by using the EIS system is compared with a high-precision commercial ZX70A impedance analyzer in the range of limited frequency of 100 Hz - 500 kHz. The result shows that the maximum relative error of amplitude and the maximum absolute error of phase are 2.42% and 0.936°, respectively. Finally, the EIS system is used to measure electrical impedance change during egg heating. The result shows that the impedance amplitude of egg decreases linearly with the increase of heating time and electrical characteristics of raw eggs and heated eggs are significantly different. These results verified that the developed EIS system achieve portable high-precision measurement of biological tissue.