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Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors.
Sensors (Basel). 2018 Nov 09; 18(11)S

Abstract

Receiving displacement sensitivities (Rx) of ultrasonic transducers and acoustic emission (AE) sensors are evaluated using sinewave packet excitation method and compared to the corresponding data from pulse excitation method with a particular emphasis on low frequency behavior below 20 kHz, down to 10 Hz. Both methods rely on the determination of transmitter displacement characteristics using a laser interferometric method. Results obtained by two calibration methods are in good agreement, with average spectral differences below 1 dB, indicating that the two calibration methods yield identical receiving sensitivities. At low test frequencies, effects of attenuation increase substantially due to increasing sensor impedance and Rx requires correction in order to evaluate the inherent sensitivity of a sensor, or open-circuit sensitivity. This can differ by more than 20 dB from results that used common preamplifiers with ~10 kΩ input impedance, leading to apparent velocity response below 100 kHz for typical AE sensors. Damped broadband sensors and ultrasonic transducers exhibit inherent velocity response (Type 1) below their main resonance frequency. In sensors with under-damped resonance, a steep sensitivity decrease occurs showing frequency dependence of f²~f⁵ (Type 2), while mass-loaded sensors exhibit flat displacement response (Type 0). Such behaviors originate from sensor characteristics that can best be described by the damped harmonic oscillator model. This model accounts for the three typical behaviors. At low frequencies, typically below 1 kHz, receiving sensitivity exhibits another Type 0 behavior of frequency independent Rx. Seven of 12 sensors showed this flat region, while three more appear to approach the Type 0 region. This appears to originate from the quasi-static piezoelectric response of a sensing element. In using impulse method, a minimum pulse duration is necessary to obtain spectral fidelity at low frequencies and an approximate rule is given. Various factors for sensitivity improvement are also discussed.

Authors+Show Affiliations

Department of Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA. ono@ucla.edu.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

30424019

Citation

Ono, Kanji. "Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors." Sensors (Basel, Switzerland), vol. 18, no. 11, 2018.
Ono K. Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors. Sensors (Basel). 2018;18(11).
Ono, K. (2018). Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors. Sensors (Basel, Switzerland), 18(11). https://doi.org/10.3390/s18113861
Ono K. Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors. Sensors (Basel). 2018 Nov 9;18(11) PubMed PMID: 30424019.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Frequency Dependence of Receiving Sensitivity of Ultrasonic Transducers and Acoustic Emission Sensors. A1 - Ono,Kanji, Y1 - 2018/11/09/ PY - 2018/10/13/received PY - 2018/11/05/revised PY - 2018/11/07/accepted PY - 2018/11/15/entrez PY - 2018/11/15/pubmed PY - 2018/11/15/medline KW - acoustic emission sensors KW - damped harmonic oscillator KW - frequency independent sensitivity KW - impulse method KW - input impedance KW - low frequency characteristics KW - minimum pulse duration KW - open-circuit sensitivity KW - receiving sensitivity KW - sinewave excitation KW - ultrasonic transducers JF - Sensors (Basel, Switzerland) JO - Sensors (Basel) VL - 18 IS - 11 N2 - Receiving displacement sensitivities (Rx) of ultrasonic transducers and acoustic emission (AE) sensors are evaluated using sinewave packet excitation method and compared to the corresponding data from pulse excitation method with a particular emphasis on low frequency behavior below 20 kHz, down to 10 Hz. Both methods rely on the determination of transmitter displacement characteristics using a laser interferometric method. Results obtained by two calibration methods are in good agreement, with average spectral differences below 1 dB, indicating that the two calibration methods yield identical receiving sensitivities. At low test frequencies, effects of attenuation increase substantially due to increasing sensor impedance and Rx requires correction in order to evaluate the inherent sensitivity of a sensor, or open-circuit sensitivity. This can differ by more than 20 dB from results that used common preamplifiers with ~10 kΩ input impedance, leading to apparent velocity response below 100 kHz for typical AE sensors. Damped broadband sensors and ultrasonic transducers exhibit inherent velocity response (Type 1) below their main resonance frequency. In sensors with under-damped resonance, a steep sensitivity decrease occurs showing frequency dependence of f²~f⁵ (Type 2), while mass-loaded sensors exhibit flat displacement response (Type 0). Such behaviors originate from sensor characteristics that can best be described by the damped harmonic oscillator model. This model accounts for the three typical behaviors. At low frequencies, typically below 1 kHz, receiving sensitivity exhibits another Type 0 behavior of frequency independent Rx. Seven of 12 sensors showed this flat region, while three more appear to approach the Type 0 region. This appears to originate from the quasi-static piezoelectric response of a sensing element. In using impulse method, a minimum pulse duration is necessary to obtain spectral fidelity at low frequencies and an approximate rule is given. Various factors for sensitivity improvement are also discussed. SN - 1424-8220 UR - https://www.unboundmedicine.com/medline/citation/30424019/Frequency_Dependence_of_Receiving_Sensitivity_of_Ultrasonic_Transducers_and_Acoustic_Emission_Sensors_ L2 - http://www.mdpi.com/resolver?pii=s18113861 DB - PRIME DP - Unbound Medicine ER -
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