New surface acoustic wave gas sensor of the mass-sensitive type sensitive to the thermal properties of gases

The basic principles of a new surface acoustic wave (SAW) gas sensor are described. Being essentially a sensor of the mass-sensitive type, the proposed device possesses certain features of the thermometric SAW sensors and is not only sensitive to the vapors of volatile substances, but capable of detecting gases by their thermal properties as well. This principles consists of making a certain delay of heat fluxes between the substrate of sensitive SAW element (SAW delay line or SAW resonator) and working surface of the sensor´s temperature stabilization system. In contrast to the known thermometric SAW sensors, the proposed sensor is characterized by high temperature stability and fast response. A variant of the sensor based on a LiNbO₃ is described and some results on detecting propane-butane mixtures are presented, glass spacers being a means providing heat flux delay between LiNbO₃ substrate and working surface of the sensor´s temperature stabilization system.