@inproceedings{HoffmannUngerHoetal., author = {Hoffmann, Maik and Unger, Alexander and Ho, Min-Chieh and Park, Kwan Kyu and Khuri-Yakub, Butrus T. and Kupnik, Mario}, title = {Volumetric characterization of ultrasonic transducers for gas flow metering}, series = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, booktitle = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2013.0336}, pages = {1315 -- 1318}, abstract = {The design of ultrasonic gas flowmeters requires a thorough three dimensional characterization of the acoustic sound field. For large pipe flowmeters, such as used for flare gas metering, the transducers are operated at frequencies ranging from 20 kHz up to 150 kHz. Thus, in this work we use a commercially available calibrated 1/8-inch microphone, mounted on a 3D positioning system for performing volumetric measurements in a volume of up to 1x1x1 m. By using proper corrections in terms of angular and free-field response of the microphone, the measurement system is efficient and delivers around 30000 measurements in about only eight hours. The data then is visualized in form of 3D figures or various slices to extract all relevant information. The system has been used to identify non-uniform velocity profiles in capacitive micromachined ultrasonic transducers (CMUTs), operating in permanent contact mode. Further, the system can be used to investigate the effect of various acoustic boundary conditions the transducers are facing when mounted inside transducer port cavities and it can be used for general model validation purpose.}, language = {en} } @inproceedings{UngerHoffmannHoetal., author = {Unger, Alexander and Hoffmann, Maik and Ho, Min-Chieh and Park, Kwan Kyu and Khuri-Yakub, Butrus T. and Kupnik, Mario}, title = {Finite element analysis of mechanically amplified CMUTs}, series = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, booktitle = {Proceedings, 2013 IEEE International Ultrasonics Symposium}, publisher = {IEEE}, doi = {10.1109/ULTSYM.2013.0074}, pages = {287 -- 290}, abstract = {We introduce the possibility of improving a single-cell capacitive micromachined ultrasonic transducer (CMUT) for air-coupled ultrasound by simply adding a hollow conical-shaped structure (horn) on top of the CMUT plate. The main objective is to improve both transmit and receive sensitivity by lowering the center-to-average displacement ratio, which for bending plate operated devices inherently is limited. In addition, for receive mode the force generated from the impinging sound pressure wave is concentrated to the center of the plate, resulting in larger signals and, in contrast to piston-shaped plates, the horn has the advantage of only moderately increasing the modal mass of the structure. By using finite element analysis and first sound pressure measurements of our modified CMUT, we demonstrate that this idea is feasible and promising for air-coupled CMUTs operating at frequencies below 150kHz, as it has been been proven to be successful for commercially available piezoelectric - driven bending plate devices as well.}, language = {en} } @inproceedings{HoHoffmannUngeretal., author = {Ho, Min-Chieh and Hoffmann, Maik and Unger, Alexander and Park, Kwan Kyu and Kupnik, Mario and Khuri-Yakub, Butrus T.}, title = {CMUTs in Permanent Contact Operation for High Output Pressure}, series = {Proceedings, ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems and ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels}, booktitle = {Proceedings, ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems and ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5690-1}, doi = {10.1115/IPACK2015-48733}, pages = {6}, language = {en} }