The use of smart Lead Zirconate Titanate (PZT) patches, in structural health monitoring (SHM) has been of much research in recent years; especially in damage detection using electro-mechanical impedance (EMI) technique which is based on the coupling relationships between the PZT and the host structure. In SHM, damage severity identification and localization are of great importance. PZT has shown excellent sensitivity in structural damage identification and has been successfully applied in SHM. However, systematic investigation on damage propagation and localization is still in need. In this study, monitoring of progressive damage using a single and multiple PZT is investigated. Experiments are carried out by creating damages progressively along longitudinal and lateral axis on plates. The patterns of variations in signatures under different levels of damage are studied. Finite element analysis is also carried out using a recently developed 3D EMI model (by Venu Gopal Madhav Annamdas).A statistical index is adopted to analyze results quantitatively. Finally a wireless sensing system was developed and tested for accuracy. This book provides useful information of PZT based SHM research.