/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.

[1]  João G. Crespo,et al.  Integrating pervaporation with electronic nose for monitoring the muscatel aroma production , 2000 .

[2]  B. Kasemo,et al.  The dissipative QCM-D technique: interfacial phenomena and sensor applications for proteins, biomembranes, living cells and polymers , 1999, Proceedings of the 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium (Cat. No.99CH36313).

[3]  P. R. Kraus,et al.  A novel sensor for monitoring oilfield fouling in near-real time , 1999 .

[4]  P. Vanýsek,et al.  Quartz crystal microbalance in electroanalytical applications , 1997, Proceedings of International Frequency Control Symposium.

[5]  N. Koprinarov,et al.  Humidity adsorptive properties of thin fullerene layers studied by means of quartz micro-balance , 1997 .

[6]  Antonio Cantoni,et al.  Precise all-digital frequency detector for high frequency signals , 2000, IEEE Trans. Commun..

[7]  G. Sberveglieri,et al.  Tin oxide gas sensing: comparison among different measurement techniques for gas mixture classification , 2001, IMTC 2001. Proceedings of the 18th IEEE Instrumentation and Measurement Technology Conference. Rediscovering Measurement in the Age of Informatics (Cat. No.01CH 37188).

[8]  Eduard Llobet,et al.  SPICE model for quartz crystal microbalance gas sensors , 1999 .

[9]  Chao Zhang,et al.  Contributions of amplitude measurement in QCM sensors , 1996 .

[10]  Shigeyoshi Goka,et al.  Fundamental study on multi-mode quartz crystal gas sensors , 1999, 1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium (Cat. No.99CH37027).

[11]  P. Hauptmann,et al.  Signal amplification with multilayer arrangements on chemical quartz-crystal-resonator sensors , 2000, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[12]  Julian W. Gardner,et al.  Modelling of gas-sensitive conducting polymer devices , 1995 .

[13]  Rongnong Zhou,et al.  Polymer-coated quartz crystal resonators for multi-information sensing , 1997 .