Conductivity sensors for water quality monitoring: A brief review

Abstract

Conductivity of water is one of the important parameters that can, to some extent, reveal the quality of water. As water quality changes, the ability of water to pass current through it changes. This makes the conductivity measurement important. Some of the conductivity sensors are designed to use for flow-through applications while some others are immersion types. Conductivity can be measured using specially designed sensors or probes; some of those need direct contact with water. There are also sensors with no such restriction. Sensors that need direct contact with water suffer due to contamination of the measurement electrodes. Accuracy of the measurement is affected by the electrode contamination, undefined current path, noise, and non-idealities of the measurement electronics employed. There are non-contact-type conductivity sensors based on inductive techniques and capacitively coupled techniques. They have no electrode contamination problem. Undefined current path in water is a limitation for the inductive-type probe and complexity level of the capacitively coupled sensor is relatively high. To select or design a certain type of conductivity sensor, it will be advantageous if the associated details are available in a concise manner. This chapter presents an overview about the existing conductivity sensors for water. It is focussed on latest developments and a performance comparison is presented by listing the limiting factors. The chapter concludes with a discussion of future opportunities in this field.