Passive wireless sensing devices for structural health monitoring

Abstract

Large scale sensor deployments for structural health monitoring (SHM) based on existing NDE equipment are limited in their application due to the challenges associated with the power supply and data acquisition. This paper presents the development of a passive sensor node and remote reader unit which aim to address these limitations and bridge the gap between traditional non-destructive evaluation (NDE) and SHM. Power is delivered to sensor nodes using an ultra-high frequency (UHF) radio link and communication is achieved using a backscatter modulation mechanism, removing any requirement for a resident power source. Results indicate that the device can be energised and interrogated from ranges exceeding 20m. The passive transponder may include ultra-low power electromagnetic, magnetic or acoustic sensing payloads within the same general acquisition and communication platform. This versatility allows for a wider range of potential applications or more diverse information about a structure. The sensor platform is based around a single low cost, micro-power microcontroller with integrated analogue to digital converter (ADC). An electromagnetic sensor payload has been developed which can perform a pulsed eddy current (PEC) measurement. The coil transient can be sampled, check-summed and digitally transmitted along with position and temperature information for an energy budget of <15μJ. Furthermore, an acoustic normal beam inspection payload has been developed which can monitor wall thickness and detect sub-surface defects within the same energy budget. \ua9 (2013) by the British Institute of Non-Destructive Testing. All rights reserved