N. Ulivieri

Selectivity enhancement of SnO2 sensors by means of operating temperature modulation

Abstract In this paper results concerning the classification of water solutions with ethanol and other volatile organic compounds by means of SnO2 sensors are presented. This study aims at the selection of the most appropriate measurement technique for this application, in terms of both selectivity and repeatability. The final aim of this research is the application of electronic noses based on metal oxide sensors to wine classification. In particular, a comparison is performed between two measurement techniques: chemical transient analysis and sensor temperature modulation.

Tin oxide gas sensing: comparison among different measurement techniques for gas mixture classification

In this paper, a study is presented aimed at the selection of the most appropriate measurement technique for wine classification. In particular, the problem of detecting typical wine aroma components in mixtures where ethanol is present is taken into account. The literature proposes different solutions in order to enhance metal-oxide sensor selectivity. An interesting approach concerns the application of different measurement techniques. In this work, three methods based on chemical transient, AC measurements, and temperature modulation have been investigated.

Electronic noses based on metal oxide gas sensors: the problem of selectivity enhancement

Metal oxide gas sensors (MOX) are widely used in olfactory systems for their high sensitivity and low-cost. These sensors vary their conductivity in presence of oxidizing and reducing gases and their performance is strictly dependant on the measurement technique adopted. In this paper the authors present results concerning the selectivity enhancement of an electronic nose based on MOX sensors, proposing also a gray-box model to describe the sensor response in presence of oxygen and CO during sensor temperature modulation.

Temperature profile investigation of SnO/sub 2/ sensors for co detection enhancement

SnO/sub 2/ sensors are widely used for the detection of air contaminants such as CO. Nevertheless, their application encounters several problems, mainly the effect of interfering gases. The low selectivity is, in fact, a well-known problem of these sensors. Moreover, the high operating temperature of metal oxide sensors implies, in general, high power consumption. We present a study aimed at the selection of an appropriate measurement technique for detection of CO for indoor applications (lower threshold 100 ppm), in the presence of high concentrations of ethanol (up to 1000 ppm), by using only one sensor. Moreover, the paper aims at developing portable CO detectors that are very small, low power, and could be battery operated.SnO/sub 2/ sensors are widely used for the detection of air contaminants such as CO. Nevertheless, their application encounters several problems, mainly the effect of interfering gases. The low selectivity is, in fact, a well-known problem of these sensors. Moreover, the high operating temperature of metal oxide sensors implies, in general, high power consumption. We present a study aimed at the selection of an appropriate measurement technique for detection of CO for indoor applications (lower threshold 100 ppm), in the presence of high concentrations of ethanol (up to 1000 ppm), by using only one sensor. Moreover, the paper aims at developing portable CO detectors that are very small, low power, and could be battery operated.

Parametric model of a polymeric chemoresistor for use in smart sensor design and simulation

Abstract A novel parametric model of a polymeric chemoresistor is proposed for application in the design and simulation of smart gas sensors. The model has been implemented using Cadence™ software and enables the simulation of both the static and dynamic response of a chemoresistor to a mixture of different gases. It also takes into account parametrically the effects of ambient temperature, humidity and sensor noise. The layout design and a schematic symbol have also been generated in Cadence -thus creating a resistive polymeric cell that can be used in the general design of smart ASIC based systems. The top cell comprises several sub-cells allowing versatility and adaptability in implementation through its modular structure. By changing the values of the simulation parameters and/or the mathematical model of the sub-cell that evaluates the gas sensor response, it is possible to extend its application to the design and simulation of chemoresistors in different configurations and with different gas sensitive materials. Here we illustrate our model in the design and simulation of resistive sensors employing carbon-black polymer composite films as the class of gas sensitive material.

Design and simulation of a smart ratiometric ASIC chip for VOC monitoring

This paper reports on the design and simulation of a novel ratiometric application specific integrated circuit (ASIC) chip for the monitoring of volatile organic compounds (VOCs) or gases. The design integrates two polymeric chemoresistors in a ratiometric configuration, together with smart circuitry, into a single chip fabricated through a standard silicon CMOS process. The circuit provides automatic compensation of signal from variations in both supply voltage and ambient temperature. On-chip control of the operating temperature of the sensors is also an option. The response of the ratiometric set of polymeric chemoresistors to different concentrations of gases at different temperatures and humidities was simulated with the aid of a novel parametric Cadence model. Simulations confirm that the ratiometric configuration is less sensitive to temperature variations and that it also has a better performance in terms of humidity dependence when compared to an individual chemoresistor. These features, together with its ability to compensate for a large range in values of polymer resistance, make us believe that the circuit offers relevant smart capabilities at a very low-cost and so it can be used as the main component for the mass production of a self-calibrating, programmable, palm-top instrument.

Versatile headspace and electronics for measurements with gas sensor arrays

A new multisensor headspace and electronics for gas detection are presented. The system is PC-based and fully software controllable and reconfigurable. It was designed to allow for a very versatile use with different metal oxide sensor elements. In particular, the system supports different measuring techniques such as sensor impedance measurement in a frequency range spanning from DC to 15 MHz, and sensor gas sensitivity measurement when the temperature follows an arbitrary-defined trend. Some preliminary results concerning wine classification are also presented.

/spl Sscr/tudy of the dynamic response of QCM sensors by means of a fast and accurate all-digital frequency detector

In this paper an innovative measurement system for odor classification, based on Quartz Crystal Microbalances (QCHs), is presented. In particular, the problem of detecting typical wine aroma components in mixtures where ethanol is present is taken into account. In QCM sensors the sensitive layer is a polymeric layer deposited on a quartz surface. Chemical mixtures are adsorbed by the polymeric layer, inducing a change in the quantz mass and therefore in its resonance frequency. The frequency shift is measured by a dedicated fully digital front-end hardware implementing a technique proposed by Cantoni (2000). This approach allows reducing the measurement time while maintaining a high frequency resolution. The developed system allows measuring variations of the QCM resonance frequency shifts during chemical transients obtained with abrupt changes in odor concentration. Hence the reaction kinetics can be exploited to differentiate among different compounds. In this study some measurements obtained with an array of 4 sensors with different sensitive layers are presented. An exponential fitting of the transient responses is used for feature extraction. Principal Component Analysis (PCA) to reduce data dimensionality is used.

LabWeb1451: Remotely Accessible Virtual Laboratory for Transducer Electronic Data Sheets Creation and Testing

In this paper the realization of a virtual remote laboratory (LabWeb1451) for developing and testing electronic datasheets (TEDS.4) compliant with the recent standard IEEE 1451.4 for plug and play sensors, is discussed. The virtual lab is a Web-based resource for students and researchers working in the sensor field: it consists of a set of software components implemented to support the development of a TEDS.4 database for resistive sensors and to experiment new generation of sensors compliant with IEEE1451.4

SnO/sub 2/ sensors with variable operating temperature for CO detection: selectivity enhancement

SnO/sub 2/ sensors are widely used for the detection of air contaminants such as CO. Nevertheless, their application encounters many problems, first of all the effect of interfering gases. The low selectivity is in fact a well-known problem of these sensors. Moreover, the high operating temperature of metal oxide sensors implies in general high power consumption. In this work we present a study aimed at the selection of an appropriate measurement technique for the detection of CO for indoor applications (100 ppm CO), also in presence of high concentrations of ethanol (1000 ppm C/sub 2/H/sub 5/OH). Moreover, the work aims at developing very low size and power consumption devices, that could be battery operated, to be used for the development of portable CO detectors.