The electro-mechanical behaviour of flexural ultrasonic transducers

Abstract

Flexural ultrasonic transducers are capable of high electro-mechanical coupling efficiencies for the generation or detection of ultrasound in fluids. They are the most common type of ultrasonic sensor, commonly used in parking sensors, because the devices are efficient, robust, and inexpensive. The simplest design consists of a piezoelectric disc, bonded to the inner surface of a metal cap, the face of which provides a vibrating membrane for the generation or detection of ultrasonic waves in fluids. Experimental measurements demonstrate that during the excitation of the piezoelectric element by an electrical voltage, there are three characteristic regions, where the frequency of the emitted ultrasonic wave changes during the excitation, steady-state, and the final decay process. A simple mechanical analogue model is capable of describing this behaviour. V C 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers

“…7 demonstrate the capability of a flexural ultrasonic transducer to detect high frequency signals in air transmitted from a source flexural ultrasonic transducer with clarity, using a burst sinusoidal signal. The absence of over-shoot in the amplitude responses for the (0,0) and (1,0) modes as the responses transition to steady-state is an indicator of the transducer being driven at its resonance frequencies [12]. This was more difficult to inspect for the response of the (2,0) mode based on the response signal noise, Fig.…”

“…In each case, the drive frequency was modulated until the output voltage amplitude reached a maximum, thus providing a reliable measure of the resonance frequency. A similar technique has been used in prior studies with burst sinusoidal signals, where a maximum vibration amplitude around an estimated resonance frequency at steady-state can be used to accurately measure that particular resonance frequency [12]. The burst sinusoidal signal method has an additional advantage, since the over-shoot in the amplitude-time response spectrum indicates a disparity between the drive frequency and the resonance frequency of the flexural ultrasonic transducer [12].…”

“…A similar technique has been used in prior studies with burst sinusoidal signals, where a maximum vibration amplitude around an estimated resonance frequency at steady-state can be used to accurately measure that particular resonance frequency [12]. The burst sinusoidal signal method has an additional advantage, since the over-shoot in the amplitude-time response spectrum indicates a disparity between the drive frequency and the resonance frequency of the flexural ultrasonic transducer [12]. The ultrasonic response profiles for the (0,0) and (1,0) modes were both measured at a distance of 500 mm in air, and the results are shown in Fig.…”

The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air

“…The FUT operates by vibrating at one of the resonant modes of the platepiezoelectric disc composite structure, with a relatively high transduction efficiency at low power and low voltage (<10 V) excitation. The simple structure is easy to manufacture, resulting in a low cost, mechanically robust transducer [20][21][22][23][24][25][26][27][28][29]. One of the principal limitations of the FUT has been the assumption that operating frequency is generally limited to below 50 kHz, with the most common operation frequency for commercially available FUTs being 40 kHz [21].…”

HiFFUTs for high temperature ultrasound

“…Each HiFFUT was then heated to 150°C in a laboratory furnace (Pyrotherm) in increments of 50°C, held at each temperature for 15 minutes, with its response monitored using an acoustic microphone. The complete experimental process is outlined in Figure 4, adapted from prior investigation 4 .…”