The TorqSense units are a new type of sensor based on patented technology that makes use of surface acoustic wave transducers. These transducers comprise two thin metal electrodes, in the form of interlocking “fingers” on a piezoelectric substrate such as quartz. When an RF signal of the correct frequency is applied to the transducer, surface acoustic waves are set up, and the transducer behaves as a resonant circuit. The essential feature, however, is that if the substrate is deformed, the resonant frequency changes. When the transducer is attached to a drive shaft, the deformation of the substrate and hence the change in resonant frequency is related to the torque applied to the shaft. For more information, visit www.sensors.co.uk.