Unpowered wireless sensors for structural health monitoring
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The rapid advancement of wireless technology has allowed the development of new sensor technologies for many different applications. Unfortunately, many of the sensor systems have a substantial cost and require a continuous power source. A new class of sensors is proposed for use in situations where cost and long-term durability are of major concern. For example, corrosion of steel reinforced concrete is a worldwide problem, with potential damages estimated at billions of dollars in the United States alone. A simple low-cost resonant-based embeddable sensor platform is proposed. The sensor is wirelessly powered and interrogated through a magnetically coupled reader coil. The sensor circuit is analyzed and a series of design guidelines are developed. Two prototype sensors, one to detect corrosion of steel reinforcement in concrete and one to measure conductivity, are proposed and tested both in the laboratory as well as in actual reinforced concrete members. The use of the wireless platform for other types of sensors is also discussed. Results indicate that the sensor platform performs well and may aid in the early detection of corrosion in reinforced concrete.