CMOS test circuit architecture for the extraction of fluid properties using interdigitated electrodes microsensors

Determining the electrical impedance of fluids is of interest in many applications such as the measurement of ionic concentration, the detection of dispersed particles or the humidity sensing. This paper shows a new test system for standard interdigitated electrodes microsensors using a single CMOS circuit that extracts the fluid impedance parameters. The system principle is to load the structure with constant current steps. The response is a voltage wave which contains the fluid resistance and the fluid capacitance in its shape. Simulations and PCB measurements prove the system ability to discriminate fluid resistive variations from fluid capacitive variations.