Impedance Of Transducer Research Articles

An application and discussion of wide-band signal processing technology in the primary calibration for hydrophones

Abstract Wide-band signals are potentially available in the measurement of transducers, which can obtain wide-band responses of electroacoustic parameters of them directly. The hydrophone of B&K 8103 is calibrated in a Φ 1.2 m×1.8 m small water vessel by wide-band signal processing technology in the frequency range of 3.15 kHz to 100 kHz. A thin pellicle co-vibrates with acoustic particle in the free-field, and its oscillation can be detected by a laser Doppler vibrometer, which can estimate the acoustic pressure distribution. The transfer function model is established in a small water vessel, and the wide-band frequency responses of the transfer impedance of transducer and hydrophone as well as the transfer impedance of transducer and pellicle in the small water vessel are calculated respectively. The wide-band signal processing technology of frequency domain filter process are used, which can isolate the reflecting acoustic wave from the boundaries and the surface of the water vessel. To verify the accuracy of the wide-band calibration measurements, the calibration results are compared with that using tone-burst signals in the water vessel and using free-field reciprocity method in the large water tank. The comparisons show that their calibration results are in a good agreement with each other, and the maximum deviation is 0.7 dB. All these demonstrate that the wide-band signal processing technology described is accurate and stable.

Research on wireless monitoring system and algorithms for preload force utilizing machine learning and electromechanical impedance

The root mean square deviation is a common way to measure the electromechanical impedance of piezoceramic transducers that are used for traditional preload monitoring. However, due to the impedance signal’s high sensitivity to temperature, most current research is carried out under the same temperature conditions to avoid its effects. Even so, it is impossible to ignore the temperature factor in practical engineering, which hinders the application of impedance technology. Therefore, this paper proposes a novel approach for preload monitoring in actual engineering: using a wireless impedance signal acquisition platform to collect long-distance impedance signals and then establishing a predicted model based on machine learning (ML) considering the temperature. The wireless impedance signal acquisition platform includes a smart washer, a piezoelectric impedance wireless sensing device, and the host computer software. This test established a dataset under various operating conditions and developed a machine-learning-based predictive model. After comparing five typical ML algorithms, it was discovered that XGBoost performed better in prediction accuracy and generalization ability. Moreover, the Shapley additive explanation method is utilized to further analyze and interpret the XGBoost model. It indicates that ML primarily relies on numerical features (such as the area of each subinterval) to identify the impedance signal and predict the prestress, whereas information features (such as temperature value, peak, etc.) have little influence on the model’s output. Finally, the results above demonstrate that the ML-based models can predict the preload at different temperatures, effectively reducing temperature interference.

Dependence of reaction on vessel position, diameter, and liquid height in the sonochemical reactor with indirect irradiation

To investigate the sonochemical reaction performance caused by the indirect irradiation at 500 kHz, the glass vessel and a KI aqueous solution were used. Both the ultrasonic power and reaction rate had maximum values at every half wavelength of ultrasound. When the vessel position was adjusted to a larger absolute value of transducer impedance, the reaction rate became higher. The reaction rate and ultrasonic power increased as the vessel position moved closer to the transducer. The reaction rate first increased as the electric power applied to the transducer increased, reached a maximum value, and then decreased. This decrease phenomenon is called quenching of the sonochemical reaction. Before the quenching occurrs, the reaction rate per unit volume almost linearly increased with ultrasonic power density. The effects of the vessel diameter and liquid height on the relationship between the reaction rate per unit volume and the ultrasonic power density were small.

A concrete shrinkage monitoring technique using embedded piezoelectric impedance transducers

A concrete shrinkage monitoring technique using embedded piezoelectric impedance transducers

Integrating a Fundus Camera with High-Frequency Ultrasound for Precise Ocular Lesion Assessment.

Ultrasound A-scan is an important tool for quantitative assessment of ocular lesions. However, its usability is limited by the difficulty of accurately localizing the ultrasound probe to a lesion of interest. In this study, a transparent LiNbO3 single crystal ultrasound transducer was fabricated, and integrated with a widefield fundus camera to guide the ultrasound local position. The electrical impedance, phase spectrum, pulse-echo performance, and optical transmission spectrum of the ultrasound transducer were validated. The novel fundus camera-guided ultrasound probe was tested for in vivo measurement of rat eyes. Anterior and posterior segments of the rat eye could be unambiguously differentiated with the fundus photography-guided ultrasound measurement. A model eye was also used to verify the imaging performance of the prototype device in the human eye. The prototype shows the potential of being used in the clinic to accurately measure the thickness and echogenicity of ocular lesions in vivo.

Numerical and Statistical Analysis of the Influence of Damage and Temperature on EMI for Structural Health Monitoring

Structural health monitoring (SHM) is a process of implementing a system to monitor the structural condition of a structure and assess the structural health. SHM is used to detect damage, predict future performance, and monitor the overall structural health of a structure. Electromechanical impedance (EMI)-based SHM is a non-destructive evaluation (NDE) technique that can be used to detect damage in structures by measuring the changes in the electrical impedance of a piezoelectric transducer that is bonded to the structure. EMI has several advantages over other NDE techniques, including being a passive, local, and relatively inexpensive technique. However, one of the challenges of using EMI for structural health monitoring (SHM) is the effect of damage and temperature on the impedance of the piezoelectric transducer. As the damage and temperature changes, the impedance of the transducer will also change. This can make it difficult to detect small damage if the damage and temperature co-exist on the same structure (aluminum plate). This research presents a numerical and statistical study to investigate the effects of damage and temperature on EMI-based SHM. The numerical model uses ANSYS software to simulate an aluminum plate at different temperatures. The findings have shown that both damage and temperature have a significant effect on the impedance of the transducer. However, the study has also demonstrated that it is still possible to detect structural damage using EMI even under varying damage and temperature conditions. This underscores the robustness of EMI-based damage detection methodologies in practical applications.

Design and Characterization of Ultrasonic Langevin Transducer 20 kHz Using a Stepped Horn Front-Mass

Ultrasonication is a method that is widely used in various fields. One of its applications is to accelerate the process of homogenization, emulsification, and extraction. In the ultrasonicator system, the transducer is an extremely important device. The resonant frequency, longitudinal vibration amplitude, and electromechanical coupling are the targets in designing an ultrasonic transducer. In this investigation, the main contribution was the development of a simple and effective method for mechanically tuning the resonant frequency of the transducer by adding mass to the front end of the mass or stepped horn. This study also aimed to obtain optimal results by examining the effects of geometric dimensions, bolt prestress, stress distribution, resonant frequency, amplitude, and electrical impedance. The ultrasonic transducer model was designed with a resonant frequency of 20 kHz and simulated using the finite element analysis. The steps involved included calculating the dimensions and geometric structure of the transducer, modeling using the finite-element method, and experimental validation. The simulation results and measurements showed that the series resonant frequency, electrical impedance, and effective electromechanical coupling of the Model-4 transducer 16∙13 mm radiator configuration were 20.15 kHz, 100 Ω, and 0.2229 from the simulation results, and 20.17 kHz, 24.91 Ω, and 0.2033 from the measurement results. A percentage difference, or relative error, of 0.1% was obtained between the simulation and the experimental results for this Model-4 with bolt prestressing at 15 kN.

Estimation Method of an Electrical Equivalent Circuit for Sonar Transducer Impedance Characteristic of Multiple Resonance.

Improving the operational efficiency and optimizing the design of sound navigation and ranging (sonar) systems require accurate electrical equivalent models within the operating frequency range. The power conversion system within the sonar system increases power efficiency through impedance-matching circuits. Impedance matching is used to enhance the power transmission efficiency of the sonar system. Therefore, to increase the efficiency of the sonar system, an electrical-matching circuit is employed, and this necessitates an accurate equivalent circuit for the sonar transducer within the operating frequency range. In conventional equivalent circuit derivation methods, errors occur because they utilize the same number of RLC branches as the resonant frequency of the sonar transducer, based on its physical properties. Hence, this paper proposes an algorithm for deriving an equivalent circuit independent of resonance by employing multiple electrical components and particle swarm optimization (PSO). A comparative verification was also performed between the proposed and existing approaches using the Butterworth-van Dyke (BVD) model, which is a method for deriving electrical equivalent circuits.

Acoustic touchless sensor using the flexural vibration of a plate

This paper investigates a method to detect the position of an object in front of an ultrasonic vibrator using changes in the radiation impedance. This acoustic touchless sensor is composed of a rectangular vibrating plate (width: 30 mm; length: 200 mm; thickness: 3 mm) and two bolt-clamped Langevin-type transducers with stepped horns. The sensor configuration was determined based on the results of a finite element analysis simulation. When a stripe flexural vibration mode excited on the plate was generated an acoustic standing-wave field in the air, the electrical impedance of the ultrasound transducers changed dramatically, thus indicating that the radiation impedance of the sensor was dependent on the object position. By measuring the amplitude of the input current to the transducers and the phase difference between the input current and the voltage applied to the sensor, the 40 mm long object’s position could be determined uniquely within a two-dimensional area of 160 × 7 mm2.

Highly Sensitive Readout Interface for Real-Time Differential Precision Measurements with Impedance Biosensors.

Field deployment is critical to developing numerous sensitive impedance transducers. Precise, cost-effective, and real-time readout units are being sought to interface these sensitive impedance transducers for various clinical or environmental applications. This paper presents a general readout method with a detailed design procedure for interfacing impedance transducers that generate small fractional changes in the impedance characteristics after detection. The emphasis of the design is obtaining a target response resolution considering the accuracy in real-time. An entire readout unit with amplification/filtering and real-time data acquisition and processing using a single microcontroller is proposed. Most important design parameters, such as the signal-to-noise ratio (SNR), common-mode-to-differential conversion, digitization configuration/speed, and the data processing method are discussed here. The studied process can be used as a general guideline to design custom readout units to interface with various developed transducers in the laboratory and verify the performance for field deployment and commercialization. A single frequency readout unit with a target 8-bit resolution to interface differentially placed transducers (e.g., bridge configuration) is designed and implemented. A single MCU is programmed for real-time data acquisition and sine fitting. The 8-bit resolution is achieved even at low SNR levels of roughly 7 dB by setting the component values and fitting algorithm parameters with the given methods.

Constant-Power versus Constant-Voltage Actuation in Frequency Sweeps for Acoustofluidic Applications.

Supplying a piezoelectric transducer with constant voltage or constant power during a frequency sweep can lead to different results in the determination of the acoustofluidic resonance frequencies, which are observed when studying the acoustophoretic displacements and velocities of particles suspended in a liquid-filled microchannel. In this work, three cases are considered: (1) Constant input voltage into the power amplifier, (2) constant voltage across the piezoelectric transducer, and (3) constant average power dissipation in the transducer. For each case, the measured and the simulated responses are compared, and good agreement is obtained. It is shown that Case 1, the simplest and most frequently used approach, is largely affected by the impedance of the used amplifier and wiring, so it is therefore not suitable for a reproducible characterization of the intrinsic properties of the acoustofluidic device. Case 2 strongly favors resonances at frequencies yielding the lowest impedance of the piezoelectric transducer, so small details in the acoustic response at frequencies far from the transducer resonance can easily be missed. Case 3 provides the most reliable approach, revealing both the resonant frequency, where the power-efficiency is the highest, as well as other secondary resonances across the spectrum.

DETERMINATION OF FARADAY IMPEDANCE PARAMETERS TO INCREASE ACCURACY IN CONDUCTOMETRY AND OBTAIN ADDITIONAL DATA

A simple algorithm for determining the set of parameters of the equivalent circuits of the impedance of a planar conductometric transducer with an interdigital comb topology, consisting of interelectrode and Faraday impedances is proposed. The frequency characteristics of the impedance parameters of the transducer samples and the electrical equivalent with averaged values of the parameters have been studied. A technique for determining the parameters of a three-element equivalent circuit, including solution resistance, double layer capacitance, and charge transfer resistance, has been developed and tested on a series of transducer samples. The optimal operating frequencies of the impedance-measuring channel are determined, and its schemes are developed. A technique for estimating the parameters of the Warburg impedance of transducer samples is demonstrated. The results obtained in the work make it possible to determine the optimal operating frequency range of biosensor systems and reduce errors from the influence of the Faraday impedance. The possibility of extending the functions of such transducers by using the near-electrode layer impedance parameters as informative ones is shown.

Thin ultrasound non-contact airborne sensor using flexural vibration

A non-contact acoustic sensing system using changes in the radiation impedance was proposed to detect the position of an object in front of an ultrasonic vibrator. The sensor is composed of a rectangular vibrating plate (20 × 100 × 1 mm3) and a PZT transducer (20 × 20 × 2 mm3). The sensor configuration was determined based on the results of a finite element analysis simulation. The flexural vibration modes were excited on the plate at two resonance frequencies, 29.7 and 46.2 kHz. The radiation angle of ultrasound from the sensor and the acoustic field between the object and the plate were compared at the two frequencies to investigate the detection characteristics. When an acoustic standing-wave field was generated in the air, the electrical impedance of the ultrasound transducers dramatically increased, indicating that the radiation impedance of the sensor was dependent on the object position. By measuring the amplitude of the input current to the transducers and the phase difference between the input current and the voltage applied to the sensor, the object position could be determined uniquely within a two-dimensional area.

Enhancing underwater Acoustic Identification Tag design using concurrent wireless ultrasonic power transfer and backscatter communication

Improvements in undersea localization and navigation of Autonomous Underwater Vehicles (AUVs) is critical. However using conventional active transponders as navigation aids is limited by powering constraints. Passive backscatter devices such as Acoustic Identification (AID)Tags are an alternate solution to this energy limitation [Satish et al., JASA 149 (2021)], but offer limited information content. To address this limitation, adding a wireless ultrasonic power transfer capability to these passive AID tags can be used to enable backscatterer uplink communication between the AID tag and an interrogating compact high-frequency SONAR system (which can be mounted on an AUV). Our design comprises a piezoelectric transducer impedance matched to a connected electrical load across two frequency ranges: a narrowband energy harvesting range, and a broadband data range. Onboard electronics harvest acoustic energy in the narrowband to power an onboard microcontroller, which can be used to simultaneously modulate the transducer broadband acoustic impedance by switching the electrical load connected to transducer during backscatter uplink communication. Water tank experiment using custom transducers, operating either around 1 MHz or 350 kHz, were conducted to quantify-amongst others-the operational source to tag distance, system power requirements and achievable communication data rates using the proposed concurrent ultrasonic power and data transfer approach.

A lumped parameter model of the longitudinal NiMnGa transducer based on piezomagnetic equations.

The NiMnGa alloy is a typical magnetic shape memory alloy with up to 6% immense strain, high energy density, and low effective elastic modulus. These comprehensive characteristics make it possible to realize a low-frequency underwater acoustic transducer. To describe the field-induced dynamic strain, an equivalent circuit model (ECM) of a longitudinal NiMnGa transducer is presented as a lumped parameter model, which couples magnetics, mechanics, and acoustics. In this paper, we focus on the piezomagnetic equations as the constitutive relationship of the NiMnGa element with a dynamic magnetic field. Furthermore, combined with the dynamic kinetic equation, the equivalent circuit is derived, and it has the advantage of containing acoustical terminals. The proposed model can predict the resonance frequency, effective stiffness, and input impedance of the NiMnGa transducer. Finally, a finite element model (FEM) is developed to verify the lumped parameter model. The results indicate that the spring's stiffness increases the resonance frequency, while the mass load is on the contrary, and they both agree well with the results of ECM. In addition, the FEM and ECM can also predict the dynamic responses, which provide a guideline for the design of longitudinal NiMnGa transducers.

Monitoring of Cylindrical Plunge Grinding Process by Electromechanical Impedance

One of the most promising monitoring techniques is based on electromechanical impedance (EMI) transducers, which are low-cost components and allow easy implementation. EMI signal features showed good results for some applications in previous studies, but it is still unexplored for machining processes, which is essential for metal-cutting industries. This paper presents a new approach to verify the applicability of EMI measurements to monitor surface quality after the plunge cylindrical grinding of non-flat parts, which require low roughness and tight dimensional tolerances. Tests were carried out in a camshaft grinder and two low-cost piezoelectric diaphragms were attached to each workpiece to guarantee redundancy. Roughness <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}_{\mathbf {a}}$ </tex-math></inline-formula> was also monitored to check existence of correlation with the EMI signals and relevant discussions regarding monitoring by EMI are presented. Results showed a great correlation between EMI measurement and surface roughness: 0.94 and 0.80 for both diaphragms. Since these diaphragms cost less than 1 US dollar and good correlation was verified, this monitoring system is promising to replace the traditional ones.

Multiparameter Analysis of the Ultrasonic Transducer Transfer Function Using a Genetic Algorithm

The transfer function is an important parameter describing ultrasonic transducers which are designed to operate in various media. The typically high impedance of piezoelectric transducers is matched to a particular loading medium (gas, liquid, biological medium) by using multicomponent matching layers, which have specific impedances and thicknesses in accordance with the generally known matching criteria: Chebyshev, DeSilets or Souquet. When properly selected, the materials used for the matching layers allow the most optimal parameters to be obtained for both transmitting and the receiving ultrasonic energy. However, studies rarely focus on the possibility of shaping the obtained transfer function, which is also a parameter that is important in some applications of transducers intended for pulse operation, especially in liquid media (e.g., in hydroacoustics) or in biological media (e.g., in ultrasound imaging). The values and shapes of such a function are influenced by factors which are identical to the parameters describing the matching layers. This article presents the possibilities and advantages of using a genetic algorithm to shape the characteristics of the transfer functions that have a particular importance in the search for an optimal (typically the greatest) bandwidth of a transducer intended for operation in a particular medium.

Ultrasonic microrheology for ex vivo skin explants monitoring: A proof of concept

As an answer to alternative non-animal testing, biosensors dedicated to the ex vivo skin explants monitoring are a challenge to study physiological-like behavior and optimize new topical products. Because of the skin viscoelastic behavior, mechanical tests are commonly based on macroscopic measurement and give global descriptors of its state. Other techniques, including photoacoustic ones, are more focused on the molecular scale. There is a gap to fill in the mesoscopic range to get information about the microstructure of the skin. This article presents the proof-of-concept of a biosensor coupling a thickness shear-mode transducer with human skin explants kept in life-like state for a week. Thanks to a multifrequency analysis of the transducer impedance, this biosensor is able to monitor the viscoelastic properties of the skin. To extract the complex shear modulus and the microstructural evolutions, a mechanical model based on fractional calculus is used. As a preliminary results, the sensitivity of the sensor to probe the skin viscoelasticity in lifelike state and the impact of its culture medium are presented. A suitable microstructural coefficient is also extracted in order to identify mechanical breaches in the skin barrier after the application of peeling products.

An experimental investigation on effects of saturation levels and fluid types on elastic properties of bitumen-saturated sands at elevated temperatures

The change of saturation levels and fluid types during steam-assisted gravity drainage (SAGD) production significantly influences elastic properties of oil sands. However, experimentally establishing petrophysical-elastic parameters relationships of oil sands that govern the SAGD process remains a challenge. Here, with modified low impedance transducers and an optimized measurement workflow, oil sands sample with varying saturation levels and fluid types are successfully investigated at varying temperatures and pressures. This is the first time that oil sands are measured at controlled bitumen-saturated levels at elevated temperatures. The results demonstrate that elastic properties of the tested sample are somewhat dependent on the pressure but strongly dependent on the temperature at varying saturation levels and fluid types. Specifically, both P- and S-wave velocities at dry conditions increase with increasing pressure but insensitive to the temperature change. However, both P- and S-wave velocities at fluid-saturated conditions are much higher than that at dry conditions mainly due to part of bitumen transforming to solid frame in low temperatures (<Liquid point) or fluid effects in high temperatures (>Liquid point). These experimental investigations qualitatively capture the elastic behaviors of bitumen-bearing sands at varying petrophysical conditions, thereby helping us in understanding the underlying processes of heavy oil production using the SAGD technique.

Analytical optimization of piezoelectric acoustic power transfer systems

Acoustic power transfer and communication through metal layers is of great interest in many applications where the integrity of metal boxes, tanks, pipes or walls must be preserved by avoiding through-hole electrical connections. While acoustic power transfer has been widely studied last decades, the optimization of such systems has not been assessed comprehensively regarding the choice of transducers’ dimensions and materials and the impact of the wall characteristic acoustic impedance. This paper stands at answering these optimization issues, using a new implementation of an analytical model and two figures of merit to evaluate performances: the power transfer efficiency and a new figure of merit, the normalized transmitted power, a crucial characteristic for electronics implementation. Among other results, we disprove the commonly used design rule stating that equalizing the characteristic acoustic impedance of wall and transducers is the best option. We propose a method to quantify the impact of acoustic impedance mismatches on performances and show that intermediary layers sized with our optimization process can solve these acoustic impedance issues, resulting in an important gain in the transmitted power (multiplied by 40 in our example) and opening up great opportunities for the acoustic power transfer technology.