CMOS-based impedance spectroscopy for water quality monitoring

Abstract

Water being used for any purpose needs to adhere to a certain quality standard. Performing tests to ensure water quality can be done in an analytical laboratory with high precision using a wide range of techniques and equipment. There is a growing need, however, for low-cost point-of-need (PON) solutions that would be able to serve a larger portion of earth’s population. One of the techniques, Impedance Spectroscopy (IS), measures the impedance of a water sample across a wide range of frequencies in order to analyse some frequency dependent properties of a sample. The problem addressed in this project is to develop an inexpensive, PON, system that can perform Impedance Spectroscopy on water samples. The impedance spectroscopy system is being developed in CMOS using the 0.35um ams AG process and will produce an impedance spectrum with frequencies ranging from 1 Hz to 10 MHz. The system interfaces with water samples through a standard three-point electrode, with voltage signals being maintained between the reference and working electrode. The analog front end for measurement as well as the digital control circuitry is included in the CMOS design.