Design of a High Frequency AC Impedance Analyzer for Biosensors

• Main Authors: HUANG,SHIH-PING, 黃世評
• Other Authors: HUANG ,CHUM-YUEH
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/2vcepb

碩士 === 國立臺南大學 === 電機工程學系碩博士班 === 107 === In this thesis, a High Frequency AC impedance analyzer is proposed for the signal processing of the electrochemical biosensor. In the proposed system, we use Direct Digital Synthesis to generate two sine wave signals with a phase difference of 90 degrees. The real resistance and imaginary reactance of the AC impedance of the biosensor can be obtained by multiplying the biosensor's current signal with two sets of sine wave signals through a multiplier (ad734), and the multiplied signal result is filtered through the low pass filter to remove the high frequency signal. Comparing with traditional impedance analyzers, the proposed system has the merits of simple circuit structure, fast detection, and intuitive signal, because the output signal of the proposed system is DC. In the system verification, an RC equivalent circuit is measured by the proposed AC impedance analyzer to obtain the real resistance and imaginary reactance at different frequency. According to the experimental results, the proposed AC impedance analyzer can achieve the frequency of 450hz~175Khz. In the future, the proposed High frequency AC impedance analyzer can be further applied in the fixed frequency AC impedance detection, and can be integrated with a low frequency AC impedance analyzer to realize a full-frequency impedance measurement system.