Designing an Eddy Current Testing Structural Health Monitoring Instrument

An instrument dedicated to Eddy Currents Testing (ECT) Structural Health Monitoring (SHM) is reported in this paper. The proposed instrument monitors the growth of a previously detected crack, performing autonomously, fully wirelessly and permanently mounted. During deployment, a terminal communicates with the Bluetooth capable processing core allowing configuration and real time measurements. When operating autonomously, low periodicity measurements are performed while cellular NB-IoT connectivity enables status and alarmistic report to a cloud infrastructure. Resonant measurement circuits based on the commercial LDC1614 integrated circuit are used to read ECT array probes with up to 8 coils. Auxiliary sensors provide visibility over environmental conditions as temperature, humidity and vibrations. Power is granted by disposable batteries and a dedicated circuit combining linear and switched regulators for high efficiency in both low power and active modes. A prototype instrument and a measurement setup were used to gather illustrate the expected operation in a real deployment scenario.