Sensitivity sensor arrays

C.W. McCarrick, D.T. Ohmer, L.A. Gilliland, P.A. Edwards and H.T. Mayfield, Fuel identification by neural network analysis of the responses of vapour-sensitive sensor arrays. Anal. Chem., 68 (1996) 4264-4269. 

Using the principles of biological olfaction, electronic nose systems contain arrays of different types of cross-reactive vapor-sensitive sensors. While it is difficult to discriminate analytes entirely by their responses to a single type of sensor, using an array of sensors yields response patterns that can readily distinguish many different vapors. Ideally, the response mechanisms of the sensors are highly varied and encompass both physical and chemical phenomena1. 

The model sensitive layer, which will be used for gas sensor performance tests throughout this book, was Sn02 that has been doped with 0.2 wt % Pd. The minute Pd-content leads to a better sensitivity to carbon monoxide. The larger response is a consequence of the increased reaction rate. For the sensor arrays in Chap. 6, two additional materials have been prepared. Pure tin oxide shows a good sensor response... 

A further peculiar characteristic of Ti02 nanotube arrays is the high H2 adsorption and mobility of H-species, which was successfully applied to develop highly sensitive sensors for These properties are of interest... 

Chemical sensors, those that measure the presence or concentration of chemical species, are the subject of this book. Until recently, they received even less attention than other sensors in general, they are not as well developed. They have the same need to be small, inexpensive, and accurate as other sensors. However, accomplishing these requirements for chemical sensors is often more difficult than for other sensors because chemical sensors are noted for interferences. For example, a chloride sensor may be sensitive to other halides. One popular way to counter this limitation is to use an array of somewhat different sensors, each responsive to the same set of related compounds but with different sensitivity. The output of the sensor array can be processed by a computer to give greater accuracy than a single sensor for the concentration of one compound. Unfortunately, this approach tends to gain better accuracy at the expense of increased size and cost. 

The key principle involved in the electronic nose concept is the transfer of the total headspace of a sample to a sensor array that detects the presence of volatile compounds in the headspace and a pattern of signals is provided that are dependent on the selectivity and sensitivity of sensors and the characteristics of the volatile compounds in the headspace [2]. 

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