Analytical microsystem for organic gas detection based on SAW devices

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Abstract
Modified SAW devices can be used as highly sensitive detectors for gases: coated with a selective sorptive layer, they serve as a frequency determining element of an oscillator circuit. To perform a quantitative and qualitative analysis of organic gas mixtures with polymer coatings as sensitive membranes, it is necessary to use an array of several SAW sensors with different sensitivities towards various gaseous components. In this work, an automatic working, self purging and compact analytical microsystem for organic gas detection is presented. As the central component it contains an array of nine SAW resonators working at an operating frequency of 433.92 MHz. Eight sensor oscillators, one common reference oscillator for temperature compensation and circuits for frequency mixing are mounted within in a compact radial housing (diameter 108 mm). A broad variety of gaseous organic analytes can be detected using this microsystem. Of particular interest are hydrocarbons, halogenated hydrocarbons and aromatic compounds. Together with an automatic pattern recognition a qualitative as well as a quantitative analysis of these gases can be achieved