Capacitive Sensor Readout Circuit for Organic Substance Analysis

Capacitive biosensors are often used for organic substance analysis like applications for food quality assurance. A biosensor readout circuit is presented in this paper capable of covering of very broad range of capacitance (up to hundreds of pF) with very good accuracy of a few fF. The readout circuit employs a current source that discharges the selected biosensor from an array of 64 ones, at time period that is proportional to its capacitance. A low cost microcontroller interfaces the fabricated integrated circuit with host computers through USB o RS232. A post processing technique implemented in the firmware of the microcontroller, filters noise and guarantees the stable operation of the proposed circuit. The high accuracy and the broad capacitance range covered, make the designed biosensor readout circuit appropriate for several applications like genetic analysis, food quality, surveillance of environmental conditions etc.