Chapter 7 - Piezoelectric Wafer Active Sensors – PWAS Transducers

Abstract

This chapter introduces the piezoelectric wafer active sensors (PWAS), which are inexpensive low-profile transducers that operate on the piezoelectric principle. PWAS transducers couple the electrical and mechanical effects through the piezoelectric constitutive equations. The chapter discusses first PWAS transducers as actuators and establishes their electric excitation range, operation with bias voltage, and effective expansion and displacement. Next, the chapter analyzes PWAS transducers as stress and strain sensors in both static and dynamic regimes. The thickness effects on PWAS excitation and sensing are discussed. The use of PWAS transducers for vibration and wave excitation and sensing is illustrated. Guidelines for PWAS installation and quality checks are given. The durability and survivability of PWAS transducers under temperature cycling, outdoor environmental exposure, submersion in operational fluids, large strains, and fatigue are discussed. Typical uses of PWAS transducers are discussed. The chapter ends with summary, conclusions, problems, and exercises.