RF-powered wireless sensor circuits for temperature monitoring

This article illustrates studies performed on four low-cost, contact-less sensing devices that transmit data telemetrically and obtain the power they need for operation from an RF wave. This type of sensor could be used to monitor a variety of physical parameters, such as temperature, pressure and strain. They can be placed in hard to reach locations such as in rotating mechanical parts, inside a given solid or in a fluid container. Specifically, the devices described are being explored as a way to monitor the temperature of mechanical structures. These circuits use no batteries and no wired connections are needed for their operation. After reviewing the intended application of the circuits, the present article describes their operational principles and discusses results from laboratory tests performed on the four prototypes.