Delay line, mass sensors

Fig. 21. A surface acoustic wave dual-delay line oscillator. The sensitise layer is placed in the propagation path of one of the two SAW devices. The differenee in Ireqnency (At) between the two channels provides a dtrecl result of the mass loading and electric field effects associated w ith the sensor layer...

Vapor sensor based on SAW devices were first reported in 1979, most of them rely on the mass sensitivity of the detector, in conjunction with a chemically selective coating that adsorbs the vapor of interest and result in an increased mass loading of the device [5]. In its simplest form SAW sensor consists of a delay line, which consists of an IDT at each end of an appropriate piezoelectric substrate. One IDT acts as transmitter and other acts as the receiver of acoustic energy which travels along... 

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