A Circuit Design for Impedance-based Structural Health Monitoring

Systems and structures monitoring their own structural integrity have become an active field. One method uses the piezoelectric impedance-based structural health monitoring technique (SHM), which utilizes a piezoelectric patch attached to a structure and measures its impedance within a certain frequency range. The frequency is maintained in the kiloHertz range for optimum sensitivity and coverage in damage detection. Owing to the coupling between electrical impedance and mechanical impedance, electrical impedance variations can indicate physical changes in the host structure. Based on the idea of a bridge circuit, a new electronic circuit to realize electrical impedance monitoring is presented (US patent pending). The proposed circuit generates a frequency sweep from 53 to 164kHz and measures the relative value of the electrical impedance modulus of a piezoelectric patch. The circuit can be integrated into a chip combined with a piezoelectric patch attached to a structure. With the help of a communication circuit, a remote SHM system can be set up in the future.