Electromechanical transducers in hostile environments

Electromechanical transducers are the primary component in many measurement systems and are increasingly called on to function in environmental extremes. The review describes how this challenge is being met, with particular reference to the mechanical measurands of strain, force/load, pressure, displacement, level and vibration. The basic principles and common forms of each transducer are first briefly described, and transducers based on novel principles or having particularly interesting applications are then discussed in more detail. A variety of fields is considered including nuclear generation, marine technology and the aerospace industry. Thin-film and semiconductor techniques have led to significant advances in strain and pressure gauges. Capacitive, inductive, magnetostrictive and piezoelectric transducers are well established and have all proved capable of great versatility: each type has a useful role to play. There is still scope, however, for new ideas as illustrated by microwave sensors being developed for strain, pressure etc. and the magneto-sonic method for measuring large displacements. The use of piezoelectric transducers at very high temperatures would probably benefit from the development of new piezoelectric materials, while the advent of piezoelectric polymer films is already having an impact on hydrophones. The possible importance of the transducer cables must not be overlooked, and there is still room for improvement in those commercially available.