Thick film chemical sensors
The development of thick film sensors is described from their early stages, where thick film technology was employed primarily for the fabrication of interface circuits and as a sensor support medium, through to their complete fabrication as screen printed sensor arrays. The concept of processing signal data from sensor arrays as a means of improving sensor performance is also introduced and examples given. These examples include the reduction of the effects of 1/f noise in thick film conductimetric sensors and the use of pattern recognition techniques applied to arrays of low specificity gas sensors to improve their selectivity to particular analyte gases. Examples of various thick film gas sensors are given and the fabrication methods and associated techniques for their use in the detection of a variety of toxic, flammable and environmental gases are described. Various sensors for liquids are described and, in particular, arrays of sensors for water quality determination. The investigation of useful lifetimes and operational performance of these devices is reported with particular reference to sensors for the measurement of temperature, conductivity, redox potential, pH and dissolved oxygen concentration in water.