APPLICATIONS OF MICROMACHINED CAPACITANCE TRANSDUCERS IN AIR-COUPLED ULTRASONICS AND NONDESTRUCTIVE EVALUATION

Micromachined capacitance transducers have been investigated in practi cal situations where air-coupled ultrasound has current application, T heir similar to 2 MHz bandwidths lead to good performance in pulse-ech o and through transmission operation at solid surfaces. Applications i n surface profiling and distance measurement have been investigated. F or the transduction of waves within solid media, the devices are shown to be capable of detecting longitudinal and shear waves at solid surf aces, as well as Rayleigh and Lamb waves. Examples are also given of f ully noncontact, through transmission of carbon fibre reinforced polym er plates.