Abstract: Leaks or thin spots in containers, as well as mechanical faults, e.g. worn bearings, are detected by an ultrasonic energy indicator that includes a modulator that heterodynes ultrasonic signals received by a transducer and creates an audio signal related thereto. The transducer includes a series arrangement of piezoelectric crystals feeding a field-effect transistor amplifier and the modulator operates in an amplitude modulation, suppressed-carrier mode which can be stabilized by a feedback loop. For indicating the presence of the audio signal, either headphones or a meter or both are employed. When leaks in a container are being detected, an ultrasonic generator is used which varies its output frequency slowly over a band of frequencies. The leak detection technique can be improved by applying a thin layer of a liquid to the container surface so that pressure introduced into the container causes the formation and bursting of bubbles in the liquid that results in the production of ultrasonic energy.

Abstract: Leaks or thin spots in containers, as well as mechanical faults, e.g. worn bearings, are detected by an ultrasonic energy indicator that includes a modulator that heterodynes ultrasonic signals received by a transducer and creates an audio signal related thereto. The transducer includes a series arrangement of piezoelectric crystals feeding a field-effect transistor amplifier and the modulator operates in an amplitude modulation, suppressed-carrier mode which can be stabilized by a feedback loop. For indicating the presence of the audio signal, either headphones or a meter or both are employed. When leaks in a container are being detected, an ultrasonic generator is used which varies its output frequency slowly over a band of frequencies. The leak detection technique can be improved by applying a thin layer of a liquid to the container surface so that pressure introduced into the container causes the formation and bursting of bubbles in the liquid that results in the production of ultrasonic energy.