SAW sensors for direct and remote measurement

SAW devices have been shown to be suitable not only for signal processing but also for sensor applications. Beginning with the early seventies of the last century, SAW sensors have been under investigation for several decades. The physical effect of a change of the elastic constants of the substrate material or a change in the mass loading under the influence of changing conditions in the environment, lead to a change in the phase velocity of the surface acoustic wave and commonly to a frequency shift in the SAW devices. Numerous solutions for sensors and sensor systems are based on this effect. However, up to now there are no mass applications for SAW sensors. On the other hand SAW sensors have some features that allow creating of unique sensor systems for measurements which are not possible otherwise. This paper will discuss some aspects of today´s status from the point of view of practical applications.