There is a growing need for advanced, cost effective, highly reliable, durable and non-intrusive systems for Structural Health Monitoring (SHM)' and Condition Based Maintenance (CBM). Of particular importance is the Structural Health Monitoring of rotating machinery (motors, generators, pumps, gear systems, etc.). Such systems should be able to detect failures in their early stages so that the repairs would be less expensive or, even better, it should be able to predict the critical conditions so that preventive actions can be taken to avoid possible damage. Determining stress in rotating machinery is a complex task and surface acoustic wave (SAW) devices provide a unique opportunity to wirelessly sense torque. In this paper, we present the results of design, fabrication, and characterization of torque sensors based on SAW technology. SAW based passive torque sensors were developed and built on quartz piezoelectric substrate using current IC photolithography techniques. A SAW sensor interrogator/reader and the associated software were developed to measure torque. The torque sensing system was tested both statically and dynamically on a specially designed test rig. Due to its small thickness and low weight, Albido's sensors can be used on moving structures with minimum loading and without disturbing the aerodynamic properties. The proposed system is low cost, low maintenance, reconfigurable, adaptive, scalable, easy to install on new or existing structures, and does not disrupt the environment.
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