A barrier layer protecting, for example, a ferroelectric capacitor from hydrogen is described. The side flange defines a fastening slot for attaching the panel to a building wall. The transducer shaft comprises a proximal end portion, a distal end portion, a drive shaft extending from the proximal end portion to the distal end portion, an ultrasonic transducer disposed near the distal end portion for obtaining a circumferential image through rotation, and a transducer housing molded to the drive shaft and the ultrasonic transducer.