Performance monitoring of ultrasonic transducers with laser vibrometers

Ultrasonic sensors are used in a plethora of industrial and medical applications, such as flow and level measurements in the process industries, blood flow measurements and tomography in medicine. The ultrasonic sensor design is very often very critical in circumventing problems associated with beam width, transmitting power and matching to the media to be interrogated by the ultrasonic signals. Surface vibrations of ultrasonic transducers depend on various design parameters and influence their directional characteristics and very often can help in diagnosing malfunctioning of the transducer due to improper bonding of active elements. A proper understanding of the form of surface vibrations can help to modify the transducer design to achieve a set of desired characteristics. This paper presents some results of vibration monitoring of ultrasonic transducers using laser vibrometry. Various transducers are probed using the laser and their performances are compared based on their membrane displacements in the order of nm. The real time analysis of laser vibrometer measurements are done by an integration of PULSE and a VI called TRANSPROBE. The focus in this paper is the integration of these programs and the analysis of the data obtained using these based on laser probing of the membrane surfaces.