Electronic Noses. Principles and Applications

The measurement and estimation of human-related senses has become an established technique in sensor research, as well as in the practical design of measurement and control systems. The electronic nose concept is widely used as an analytical tool in industry today. The commercialization of the electronic nose began in 1993 as the concept became widely accepted as an effective instrument for detection and estimation of olfaction. The book describes the general set-up of an electronic nose: it consists of an array of chemical sensors; an air flow system, which switches the reference air and the tested air; a signal analysis technique; and a presentation unit. The main sensor principles presented in the book are also the most frequently used techniques for gas sensors. These are based on two main types of gas sensor: metal-oxide semiconductors and conducting polymer resistive materials. An overview of other gas sensor principles is also given, for example, gas sensors based on the effect of sorbed molecules on the propagation of acoustic waves; field effect semiconductors; electrochemical oxidation and reduction principles; and a catalytic gas sensor. Pellistors are described as well as fibre-optic gas sensors. To increase the complexity of the odour system, an array of mixed sensing principles is often designed, consisting of different types of sensor, in order to create differences in operating temperatures, flow conditions and sensor response times. The analysis technique used, in most cases, is a supervised artificial neural network used in a relative based measurement approach, although other techniques are also mentioned in the book.