ABSTRACT
Piezoelectric sensors use the piezoelectric effect as the principle of operation. Piezoelectric sensors can be classified as being either passive or active. When the piezoelectric sensor is used as an active sensor, an energy source such as an AC electric field or voltage is used. A knowledge of the electrical and mechanical properties of piezoelectric materials is important in the design and operation of a piezoelectric sensor. In general, these properties are described by the constitutive equations, which relate mechanical forces such as stress and strain to electrical properties such as electric field and electric displacement. The choice of the piezoelectric material to be used for the sensing element is dependent upon the specific application of the stress/pressure sensor. Surface acoustic waves (SAWs) are excited on the sensing surface of a piezoelectric crystal by means of an interdigital (IDT) electrode configuration. The common SAW sensor configuration consists of two identical SAW devices fabricated on a single piezoelectric substrate.
