Enhancing the spectral signatures of ultrasonic fluidic transducer pulses for improved time-of-flight measurements

Bühling, Benjamin; Maack, Stefan; Schweitzer, Thorge; Strangfeld, Christoph

doi:10.1016/j.ultras.2021.106612

Cited by 7 publications

(7 citation statements)

References 60 publications

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“…While such differences have little effect in the application of ultrasonic non-destructive testing, they measurably affect the correlation result of Equation ( 11 ). The different spectral energy distributions cause a difference in the measured signal period lengths and thus in the envelope shapes, with the latter contributing significantly to the correlation output [ 29 ]. This systematic effect is, however, included in the hardware delay of Equation ( 12 ) and can thus be corrected.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Figure 8 d). A higher correlation peak-to-peak ratio may be achieved by generating a Dirac-like acoustic pulse [ 61 ] or by using pulse compression techniques [ 21 , 22 , 29 , 57 ] that generate a single peak in the correlation output.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Since most fluid-coupled ultrasound transducers are triggered electronically, their trigger time can be determined very exactly. However, this is not always the case, as demonstrated by the recently introduced fluidic ultrasonic transducer [ 28 , 29 ]. Although this device is triggered electronically, the sound generation mechanism is governed by fluid turbulences and cannot be controlled precisely, resulting in jitter in the 10–100

s range.…”

Section: Introductionmentioning

confidence: 99%

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Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique

Bühling

Küttenbaum

Maack

et al. 2022

Sensors

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Ultrasonic time-of-flight (ToF) measurements enable the non-destructive characterization of material parameters as well as the reconstruction of scatterers inside a specimen. The time-consuming and potentially damaging procedure of applying a liquid couplant between specimen and transducer can be avoided by using air-coupled ultrasound. However, to obtain accurate ToF results, the waveform and travel time of the acoustic signal through the air, which are influenced by the ambient conditions, need to be considered. The placement of microphones as signal receivers is restricted to locations where they do not affect the sound field. This study presents a novel method for in-air ranging and ToF determination that is non-invasive and robust to changing ambient conditions or waveform variations. The in-air travel time was determined by utilizing the azimuthal directivity of a laser Doppler vibrometer operated in refracto-vibrometry (RV) mode. The time of entry of the acoustic signal was determined using the autocorrelation of the RV signal. The same signal was further used as a reference for determining the ToF through the specimen in transmission mode via cross-correlation. The derived signal processing procedure was verified in experiments on a polyamide specimen. Here, a ranging accuracy of <0.1 mm and a transmission ToF accuracy of 0.3μs were achieved. Thus, the proposed method enables fast and accurate non-invasive ToF measurements that do not require knowledge about transducer characteristics or ambient conditions.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

s range.…”

Section: Introductionmentioning

confidence: 99%

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Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique

Bühling

Küttenbaum

Maack

et al. 2022

Sensors

Self Cite

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“…2b), the about 2 ms interval of switching on, features three distinct ultrasound peaks at 30 kHz, 43 kHz, and 57 kHz. These values are averages of 40 recorded pulses, while each has slightly varying frequency content due to their origin in turbulent flow [21].…”

Section: Signalmentioning

confidence: 99%

OsciCheck: A Novel Fluidic Transducer for Air-Coupled Ultrasonic Measurements

Bühling¹,

Maack²,

Strangfeld³

2022

eJNDT

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Ultrasonic measurement technology has become indispensable in NDT-CE. Air-coupled ultrasonic (ACU) measurement techniques promise to reduce measurement time. However, the signal quality suffers from large specific impedance mismatch at the transducer-air and air-specimen interface. Additionally, large pressure amplitudes are necessary for the penetration depth required in NDT-CE applications. To address the specific requirements of ultrasonic testing in NDT-CE, a robust ACU transducer was developed, that generates ultrasound by quickly switching a pressurized air flow. The simple design of the fluidic transducer makes the device maintenance free and resilient against harsh environmental conditions. Since the signal is generated by aeroacoustics, there is no specific impedance mismatch between the transducer and the surrounding air. The ultrasonic signal exhibits frequencies in the 30-60 kHz range and is therefore well suited to penetrate heterogenous materials such as concrete. This contribution gives an introduction in the working principle and signal characteristics of the fluidic transducer. Its application on different materials is validated. A detailed outlook is given to discuss the future potential of fluidic ultrasonic actuators.

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“…Air-coupled ultrasonic transducers have found many applications in fields such as automotive, robotics, haptics, communication, flow measurement, and nondestructive testing [1][2][3][4][5][6]. Conventionally, ultrasonic transducers are composed of piezocomposites, and acoustic matching layers have been widely studied and commercialized for decades.…”

Section: Introductionmentioning

confidence: 99%

Bottom-up micromachined PZT film-based ultrasonic microphone with compressible parylene tube

Huang,

Feng

2023

J. Micromech. Microeng.

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This paper reports on a micromachined ultrasonic microphone using a bottom-up fabrication scheme. Starting with a 4μm-thick titanium foil as the substrate, each functional film and key element was added to the foil substrate to complete the ultrasonic microphone. The piezoelectric PZT film hydrothermally grown on the patterned substrate with low residual stress effectively deflected the unimorph-sensing cantilever array of the microphone under ultrasound pressure. The created cantilever array structure secured on a 250μm-thick SU8 hollow plate formed an ultrasonic microphone plate that was tested with a sensitivity of −60 dBV/Pa at 21 kHz (with 0 dB gain amplification) and an operation bandwidth of 5 to 55 kHz. Different thicknesses of parylene films ranging from 0.5 to 2 μm overlaid over the entire sensing region and converted the cantilever-to-diaphragm-structured microphone for further investigation. An enhanced result was observed when the deposited parylene film thickness was in the submicron range. The sensitivity of the microphone can be further enhanced by up to 33% by adding a parylene-film-made compressible tube to act as a Helmholtz resonator. The Helmholtz resonator model was discussed and compared with the experimental results. The output amplitude of the developed microphone assembled with the compressible tube demonstrates a 15 dB increase compared to that of a commercial capacitive MEMS ultrasonic microphone.

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Enhancing the spectral signatures of ultrasonic fluidic transducer pulses for improved time-of-flight measurements

Cited by 7 publications

References 60 publications

Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique

Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique

OsciCheck: A Novel Fluidic Transducer for Air-Coupled Ultrasonic Measurements

Bottom-up micromachined PZT film-based ultrasonic microphone with compressible parylene tube

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