Abstract
Flexural ultrasonic transducers are principally used as proximity sensors and for industrial metrology. Their operation relies on a piezoelectric ceramic to generate a flexing of a metallic membrane, which delivers the ultrasound signal. The performance of flexural ultrasonic transducers has been largely limited to excitation through a short voltage burst signal at a designated mechanical resonance frequency. However, a steady-state amplitude response is not generated instantaneously in a flexural ultrasonic transducer from a drive excitation signal, and differences in the drive characteristics between transmitting and receiving transducers can affect the measured response. This research investigates the dynamic performance of flexural ultrasonic transducers using acoustic microphone measurements and laser Doppler vibrometry, supported by a detailed mechanical analog model, in a process which has not before been applied to the flexural ultrasonic transducer. These techniques are employed to gain insights into the physics of their vibration behaviour, vital for the optimisation of industrial ultrasound systems.
Highlights
Air-coupled ultrasound has become more prominent in recent years, due to advances in ultrasonic transducer design and fabrication [1], where more complex fabrication techniques have enabled the production of devices which are better suited to coupling with an air medium in order to propagate ultrasound signals to a target
Micro-machined transducers possess improved bandwidth and coupling with air [6], and two configurations which have been successfully applied for air-coupled ultrasound include the piezoelectric micro-machined ultrasound transducer (PMUT) [7,8], and the capacitive micro-machined ultrasound transducer (CMUT), which is characterised by a wide bandwidth and excellent air-coupled performance [9,10,11]
The PMUT and CMUT contain very small and thin membranes, and are effectively flexural transducers that are driven off membrane resonance
Summary
Air-coupled ultrasound has become more prominent in recent years, due to advances in ultrasonic transducer design and fabrication [1], where more complex fabrication techniques have enabled the production of devices which are better suited to coupling with an air medium in order to propagate ultrasound signals to a target. In the steady state region, standard of operation may not be concerning pragmatic, or the time duration of such signals may not facilitate thethe required dynamic relationships forced harmonic excitation are applicable [16]. Once again,the classical mathematical relationships can beofused to model this response occurs, known as ring-down This is the third region, and again, classical mathematical transducer behaviour [16], where the magnitude of system damping determines the time required relationships can be used to model this zero transducer behaviour [16], where the magnitude of system for the FUT vibration response to reach amplitude. In practical applications in flow measurement and ultrasound generation, FUTs to be FUTs tend to betend operated operatedmuch without much consideration of theofphysics of the vibration approaching steady-state.
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