Characteristics Of Transducers Research Articles

Особенности лазерно-виброметрического неразрушающего контроля полимерных композиционных материалов с использованием воздушно-связанных ультразвуковых преобразователей

Laser doppler vibrometry is being increasingly used in nondestructive testing (NDT) of polymer composites materials (PCM) and investigation of amplitude-frequency characteristics of acoustic transducers in a wide range of frequencies. The use of air-coupled transducers allows non- contact NDT thus expanding inspection potentials and simplifying, in some cases, test procedures, as well as reducing the environmental impact on test results, to compare to traditional techniques of acoustic NDT, which mainly implement contact stimulation of objects to be tested. In this study, the peculiarities of non-contact ultrasonic stimulation in application to NDT are analyzed by using scanning laser vibrometry. The results of NDT of impact damage in PCM are presented by using some types of air-coupled acoustic transducers, namely, magnetostrictive, piezoelectric and gas discharge.

Symmetric Reflector Ultrasonic Transducer Modeling and Characterization: Role of the Matching Layer on Electroacoustic Performance.

Symmetric reflector ultrasonic transducers (SRUTs) are a new type of ultrasonic transducer that take advantage of the ultrasonic wave emitted on the rear face of the active element. In this work, the electroacoustic modeling and characterization of such a structure is reported. Using the well-known Krimholtz, Leedom, et Matthaei (KLM) model, the electroacoustic response of a SRUT based on a piezoelectric ceramic with one matching layer is calculated. Simulations show that the optimal acoustic impedance of the matching layer should be lower than for conventional transducers, leading to a relative bandwidth of approximately 50%. The characterization of such a transducer based on a piezoceramic plate has been carried out. Bandwidth and sensitivity are reported. They are found to be close to the simulation results and demonstrate that these new types of transducers need to be designed according to new rules compared to conventional ones.

Multifrequency ultrasonic transducers based on dual vibration and harmonic mode

Multifrequency ultrasonic transducers have broad application prospects in the field of biomedical due to their high imaging resolution and detection depth. This paper proposed a design method of triple frequency single-element transducers by finite element method(FEM). The triple frequency transducers are based on contour mode, thickness mode and the third harmonic of thickness mode. Nine micro single element transducers with different widths and matching layers were fabricated and characterized to verify the design method. The traditional 30 MHz single frequency transducer and 2.3 MHz 1–3 piezoelectric composite transducer were used to compare with high frequency part and low frequency part of the triple frequency transducers, respectively. The pulse-echo characteristics of the triple frequency transducers have impressive low and middle frequency part. The high frequency part is similar with traditional transducer except the sensitivity is 0.5 times. The results certify the feasibility of a triple-Frequency transducer based on dual vibration and harmonic modes.

Methods of reduction of interference signals in electromagnetic conductors that measure fluid flow

The pressure in the fluid flow, especially in the pipes of closed water supply systems, is generated mainly by pumps, and the water flow is usually pulsating. Electromagnetic transducers used to measure such nonstationary and pulsating fluid flow rates must have low inertia and high dynamic accuracy. In such cases, the frequency characteristics of electromagnetic transducers that measure fluid flow are their main parameters. It should be noted that the performance of the converters used to measure the flow rate of pulsating fluids should not depend on the change in the distribution profile of the flow velocities, otherwise additional measurement errors will occur. It is used in measuring non-stationary and pulsating fluid flow rates in controlled and controlled technological processes.

Enhancing the Performance Characteristics of Piezoelectric Transducers by Broadband Tuning

Effect of broadband tuning in improving the performance characteristics, especially in receive mode, of a piezoelectric transducer working in the sonic frequencies is presented. The broadband tuning technique results in a frequency response function characteristic of a bandpass filter with significant improvements in SNR. When represented by an electrical equivalent circuit, the transducer resembles a half-section bandpass filter. Filter of higher order is obtained by adding external components for enhancing the bandwidth. The circuit parameters are determined from the measured electrical admittance of the transducer in the water. The transducer characteristics with broadband tuning network are simulated and validated experimentally. The impedance phase has improved from −70° to 0 ±20° over a broadband leading to an increase in power factor from 0.3 to close to 1. An enhancement of 3 dB in Source Level, 10 dB in Receiving Sensitivity, and 10 dB in Figure of Merit are obtained with 11 kHz increase in bandwidth. An improvement of 7 dB in the noise figure and SNR is also obtained in the receiving mode. The model results are in close agreement with the measured data validating the model. It is found that the broadband tuning network enhances the transducer performance simultaneously in transmitting and receiving modes. This is a significant improvement over conventional shunt tuning and is useful for stand-alone, energy-efficient sonars and two-way acoustic communication systems. The present studies demonstrate that broadband tuning methods in general, originally developed for RF and ultrasonic domains, are applicable in the sonic frequencies also.

Use of the pass-through method to solve sound radiation problems of a spherical electro-elastic source of zero order

In the article was solved the problem of radiation of a sound by the electroacoustic transducer which is executed in the form of a thin spherical cover, using a pass-through method. The outer and inner surfaces of the shell are completely electroded.
 The application of this method provides an opportunity to avoid inaccuracies that arise during the traditional formulation of boundary conditions for acoustic mechanical fields, the use of equivalent substitution schemes and the absence of boundary conditions for the electric field in general. Given methodology eliminates these shortcomings by applying conjugation conditions, taking into account the types of electroding of the surfaces of piezoceramic transducers, the introduction of boundary conditions for current and voltage. The results of the solution demonstrate the high capabilities of this pass-through method, in terms of taking into account the peculiarities of determining the characteristics of these fields, values and dependences of the main complex characteristics of the electroelastic transducer, and auxiliary material constants of the piezoelectric material.
 The proposed approach is relevant, because it allows to increase the reliability of modeling the operating conditions of acoustic transducers in the context of wave problems of acoustics. Aim is to enhance the range of performances and build algorithms solving problems of stationary mode hydroelectroelasticity sound radiation. The expected results are presented in terms of improving approaches to studying the features of the oscillatory process of the active elements of sound-emitting systems and the accompanying effects of the transformation of interconnected fields involved in the formation of the acoustic signal in the liquid

Vibration characteristics of two-dimensional orthogonalcomposite sandwich piezoelectric circular transducer

Vibration characteristics of two-dimensional orthogonalcomposite sandwich piezoelectric circular transducer

Study of the main parameters of the capacitive converter

Determination of the main parameters of a capacitive humidity transducer with a cylindrical electrode is an urgent task. The article discusses the time characteristics of a capacitive humidity transducer with a cylindrical electrode. Experimental and calculated results show that the reliability of the cylindrical transducer is 0.95. The sensitivity depends on the figure of merit of bulk materials and on the design properties of the cylindrical transducer.

Self-heating phenomenon of piezoelectric elements excited by a tone-burst electric field

Tone-burst excitation is often used for ultrasonic transducers of specific operation modes or for overcoming transducer overheating problems associated with continuous wave (CW) excitation. In this study, a theoretical model for the self-heating phenomenon of a piezoelectric disc element is established to estimate the temperature rise induced by a tone-burst electric field. An analytical solution for the temperature rise of the piezoelectric element is obtained by using Laplace transform method. Numerical simulations and experimental measurements are performed to investigate the influence of different excitation parameters on the temperature rise. By comparing the experimental results with the simulation results, the temperature-rise difference between tone-burst and CW excitations is quantified, and the validity of the theoretical model is verified. Furthermore, a multiparameter estimation method is proposed for the heat convection coefficient and dielectric properties under high-field operating conditions. These results are useful in both optimization of heat dissipation performance and characterization of high-power ultrasonic transducers.

Characterization Techniques of Millimeter-Wave Orthomode Transducers (OMTs)

We report on advanced techniques for the accurate characterization of millimeter-wave Orthomode Transducers (OMTs) enabling the derivation of the fundamental parameters of such devices, i.e., the insertion loss, the return loss, the cross-polarization, and the isolation. These techniques include standard frequency-domain and time-domain VNA (Vector Network Analyzer) measurement methods, which can be applied to remove the effects of the waveguide transitions necessary to access the OMT ports and excite the desired modes. After reviewing the definition of the OMT parameters, we discuss the test equipment, the VNA calibration procedures as well as the VNA time-domain time-gating method for application in OMT characterization. We present simplified equations that relate the calibrated VNA measured quantities with the OMT S-parameters, illustrate various characterization methods, and examine various OMT experimental test setups. The advantages and disadvantages of each of the OMT characterization procedures are presented and compared among them. We provide a list of waveguide components required in the OMT test setups (adapters, loads, quarter-wave and longer waveguide sections, feed-horn, etc.), discuss the error terms introduced by such components and examine their impact on the measured values. Furthermore, we identify strategies to mitigate or remove the effects of the measured errors, to derive the desired OMT parameters. Different OMT configurations, with a distinct orientation of the waveguide input and outputs, are discussed. Although the presented techniques refer to the characterization of a specific configuration of a W-band OMT, the described methods can be applied to other OMT configurations and frequency ranges (from microwave to THz frequencies), therefore having a general validity.

Maximum power point of magnetoelectric transducer for wireless power transmission

In this contribution, we propose an experimentally validated system-level model of a magnetoelectric transducer and a general methodology for future characterization of similar transducers. This methodology provides insights into the main origin of power losses. An analogy with piezoelectric generators leads to a system-level figure of merit which is strongly impacted by the nonlinear behavior of the transducer. Considering the complexity of the observed nonlinear behavior, we opt for a grey-box model of the dependencies between the transducer characteristics and the operating point. Applying our methodology to an optimized sample shows that nonlinear mechanical losses are the main origin of power dissipation. The maximum transferable power is proven to be up to 61% lower than the power one would expect from a linear characterization.

Comparison and analysis of electroacoustic characteristics of high power density compact low frequency hydroacoustic transducers

Typical features and principal differences of electroacoustic characteristics and impedance spectra of compact low-frequency hydroacoustic piezoelectric radiators of high power-density to-weight ratio of the longitudinal-bending, oncoming-piston and inertial-bending types are presented in the paper. Analysis and comparison of electroacoustic characteristics of differ-ent types transducers allow to clear the direction of design search. This is also important to specify technical solutions to overcome contradictions between compact dimensions, band-width, sensitivity, low resonance frequency and efficiency of hydroacoustic radiators. Using the considered types of transducers for different classes of hydroacoustics applications are suggested.

Helium-graphene optical-acoustic converter of extreme ensitivity

The prospects for the use of single-layer graphene in the design of optical-acoustic converters (OAC) of a new generation are considered. It is shown that the limiting characteristics of transducers with single-layer graphene membranes can be obtained only in OACs constructed according to the Hayes scheme. The main characteristics of membranes – the main elements of OAC – are considered, and the physical properties of graphene, as the most preferred mate-rial for membranes, are analyzed. Estimates having been made show that the use of SLG gra-phene membranes makes it possible to create IR and THz radiation receivers with cells of the order of tens of microns with extremely high sensitivity. To achieve the maximum sensitivity, it is proposed to perform edge perforation of graphene membranes. A new design scheme of uncooled helium-graphene optoacoustic receivers with theoretically maximum sensitivity and speed and an operating range extended to helium temperatures is proposed. The de-scribed technical solutions can be used as the basis for the design of uncooled.

Energy conversion models and characteristics under various inner connections of a novel packaged piezoelectric transducer for pavements

The piezoelectric effect in piezoelectric transducers converts the mechanical energy into electrical energy to supply power to road facilities. The piezoelectric transducer designed in the 3–3 piezoelectric mode has been widely studied due to the consideration of power generation performance and load-bearing requirements. However, the conservative design of some external packages and the lack of theory in the internal connection design are two deficiencies of existing research on 3–3 piezoelectric mode transducers. Given the shortcoming of packages cannot make full use of the compressive properties of piezoelectric ceramics which weakens the energy conversion ability of the piezoelectric transducers, a novel piezoelectric transducer with full-pressure packaging was designed. For the lack of theoretical and systematic research on the spatial arrangement and electrical connection of piezoelectric materials inside piezoelectric transducers, from a theoretical point of view, the energy conversion models of piezoelectric transducers in four connection modes: stacked series, stacked parallel, array series, and array parallel were derived. Subsequently, through model verification tests, the influence of the four connection modes on the energy conversion characteristics of the piezoelectric transducer was systematically studied. Finally, the effect of connection mode on energy conversion was explained in a unified manner. Five methods of promoting the energy conversion of piezoelectric transducers were proposed. The study indicated that the connection mode affected the energy conversion of the piezoelectric transducer. Specifically, the maximum energy conversion potential of the piezoelectric transducer is only affected by the spatial arrangement. The electrical connection method determines the matching resistance, which can facilitate the piezoelectric transducer to exert the maximum energy conversion potential. In the stacked type, the peak energy conversion monotonously increases with the number of stacked layers, whereas the array type exhibits the opposite trend. Regardless of the spatial arrangement of the piezoelectric materials, when piezoelectric ceramics are connected in series, the optimal value of resistance increases with the number of piezoelectric ceramics, and the opposite is true when the connection is made in parallel. The normalization analysis pointed out that the connection mode affects the energy conversion of the piezoelectric transducer can be summarized as the volume index of the piezoelectric ceramic group affects its energy conversion. A larger ratio of height to diameter of the piezoelectric ceramic group can improve the energy conversion of the transducer. This article provides ideas for the packaging design of piezoelectric transducers and a theoretical reference for the design of internal piezoelectric ceramic connection methods.

Vibration and acoustic radiation characteristics of cylindrical piezoelectric transducers with circumferential steps

Circular cylindrical transducers have a wide range of applications in ultrasound generation. Introducing axial or circumferential stepped-thickness variations affects the performance of these transducers. This paper investigates the effect of circumferential stepped-thickness variations on the vibration and acoustic characteristics of a circular cylindrical piezoelectric shell. FEM software ANSYS is used to simulate these characteristics and experiments are performed to validate the simulations. Stress concentration levels due to these steps are observed in order to avoid exceeding the material limit. The results show that these steps can excite certain mode shapes which produce strong ultrasound fields and these modes have circumferential wave numbers commensurate with the number of stepped regions. These steps localize the vibration within the thin-walled regions leading to higher amplitude acoustic waves produced by constructive interference. Superiority of a circumferentially stepped transducer over an axially stepped one is demonstrated in this study through a much more uniform acoustic field along the length of the transducer as well as a lower frequency of operation at the intended mode shape. The effect of input excitation is also investigated and it is shown that introducing circumferential steps is more effective in terms of acoustic amplification than increasing the input excitation for the uniform-thickness transducer.

Development and validation of low-intensity pulsed ultrasound systems for highly controlled in vitro cell stimulation

This work aims to describe the development and validation of two low-intensity pulsed ultrasound stimulation systems able to control the dose delivered to the biological target. Transducer characterization was performed in terms of pressure field shape and intensity, for a high-frequency range (500 kHz to 5 MHz) and for a low-frequency value (38 kHz). This allowed defining the distance, on the beam axis, at which biological samples should be placed during stimulation and to exactly know the intensity at the target. Carefully designed retaining systems were developed, for hosting biological samples. Sealing tests proved their impermeability to external contaminants. The assembly/de-assembly time of the systems resulted ~3 min. Time-domain acoustic simulations allowed to precisely estimate the ultrasound beam within the biological sample chamber, thus enabling the possibility to precisely control the pressure to be transmitted to the biological target, by modulating the transducer's input voltage. Biological in vitro tests were also carried out, demonstrating the sterility of the system and the absence of toxic and inflammatory effects on growing cells after multiple immersions in water, over seven days.

Design and Output Characteristics of Ultrasonic Transducer Based on Rare-Earth Giant Magnetostrictive Material

A new type of rare-earth giant magnetostrictive transducer, working in ultrasonic frequencies, is designed by the structural dynamic model and the dynamic coupling model. Based on the vibration, wave and frequency equations, the structural dynamic model of the transducer is established. By using COMSOL Multiphysics software parametric design method, considering the influence of materials, shapes and dimensions on the output characteristics of the transducer, the optimum mechanical structure of the ultrasonic transducer is determined. The magnetic circuit structure is analyzed by the dynamic coupling model based on the Jiles-Atherton model, Maxwell’s equations and magneto-mechanical coupling effect. The prototype of the ultrasonic transducer is fabricated. The relationship between the output characteristics and the frequency is studied. The results demonstrate that the ultrasonic transducer can work in the range of 18-22 kHz, and exhibits higher magneto-mechanical conversion efficiency at the frequency of 19.5 kHz.

A software-hardware unit for studying the output characteristic of MEMS pressure sensors and its linearization

The paper presents the development of a linearization algorithm of the output parameters of the sensors based on the circuits that determine the static characteristics of the correction transducers, ensuring the linearity of the general conversion function with a given accuracy. Simulation modeling of correcting the output parameters of MEMS pressure sensors has been carried out. The qualitative characteristics of the measuring system are determined via providing the sensors with a means for determining the degree of reliability of their output data using a virtual exemplary tool. A technique for calibrating and linearizing the output characteristic of an analog MEMS pressure sensor has been developed. An algorithm for polynomial approximation of the nonlinear output characteristic of the sensor and a method for its implementation in Lab View software environment (by National Instruments) are presented. Virtual instruments developed in Lab View software environment have been the basis of software-hardware means for monitoring and processing of measuring data. The developed methodology and means of automation of measuring processes with the use of virtual devices made it possible to make the process of correcting the output parameters of sensors autonomous, independent of stationary measuring devices and debugging tools.

Development of an Equivalent Circuit of a Cymbal Transducer

The cymbal transducer is a miniature transducer developed from the class V flextensional transducer. Many studies to analyze this transducer have been conducted using either the finite element method or fabrication and measurement technique. Meanwhile, the equivalent circuit method is a relatively simpler, faster, and more efficient approach to conduct performance analysis of an electromechanical transducer compared with these two methods. However, despite this merit, an accurate equivalent circuit model has not been introduced for the cymbal transducer, yet. In this study, we developed a novel equivalent circuit that can accurately depict the characteristics of the cymbal transducer and enable its efficient performance evaluation. The equivalent circuit was first divided into several parts according to the structure of the transducer. Thereafter, the electromechanical and vibration characteristics of each part were analyzed to derive the values of the circuit parameters corresponding to the part. The validity of the circuit parameters was verified by comparing the impedance calculated with the circuit comprising the parameters and that measured with prototype transducers. Additional analysis of the transmitting voltage response of the transducer further confirmed the efficacy and accuracy of the developed equivalent circuit in characterizing the cymbal transducer. The new equivalent circuit developed in this work can facilitate the design and analysis of not only individual cymbal transducers but also their large arrays.

Engineering the electromechanical response of piezoelectric transducers: Some challenging applications

Piezoelectric transducers are widely used for ultrasonic applications both as actuators to excite and as sensors to receive vibration/wave response. The electromechanical characteristics of the piezoelectric transducers dictate their choice for specific applications. These can be tuned in several ways ranging from modifying the geometry and material properties of the element to changing the excitation electrode pattern and the boundary conditions of the vibrating piezoelectric element. This talk discusses two different ways to achieve such tuning for single-element piezoelectric transducers and their corresponding applications. The first application is to achieve a low-frequency collimated beam using lateral stiffening of a piezoelectric disc vibrating in its radial resonance. The resonance and vibration characteristics of such a disc are presented and the ultrasonic wave propagation from such a laterally stiffened disc in fluids is discussed. The second application uses tailored polarization profiles for piezoelectric elements to enhance/suppress specific resonant modes in an otherwise homogeneous element. The fundamental theory for such behavior is presented and some applications of such polarization-tuned piezoelectric elements are discussed.