Re: measuring paper : There is some good information available in regards to your paper testing project: : I am referring to the publications from M. Luukkala: : 1) M. Luukkala, "Tenscan, an Acoustic NDE Device to Measure Tension in a Moving Paper Web" in 1990 Rev.Prog.in QNDE, D.O. Thompson and D.E. Chementi eds. (plenum, New York, 1990) pp.1987-1981 : 2) M.Luuukkala, P. Heikkila and J. Surakka: "Plate wave resonance- a contactless test method. Ultrasonics, October 1971. Editors are the Department of Technical Physics, Helsinki & Universtity of Technology, Otamiemi, Finland : (Remark: VERY IMPORTANT PAPER) : 3) M. Luukkala and P. Merilainen: "Metal Plate testing using airborn ultrasound. : 4) Department of Physics, University of Helsinki, Finland 11 April 1973. : 5) In regards to further references, transducer types and applications, you may like to look at: : "NDE Applications of Air-Coupled Ultrasonic Transducers" W.A. Grandia and C.M. Fortunko. IEEE Ultrasonics, Ferroelectrics, and FrequencyControl. Novenber 7 - 10, 1995. : 1995 IEE International Ultrasonic Symposium, Seattle, Washington.
: At our laboratory: QMI Inc. 919 Sunset Drive, Copsta Mesa, CA 92627 USA., we have developed an air-coupled ultrasonic instrument: SONDA-007. It can operate at discrete toneburst mode (200kHz, 400 kHz and 1 MHz). This device may be used to launch platewaves into paper sheet and detectr the through transmitted signals. It is possible to transmit signals over a fairly long distance. : If you have trouble finding the papers, please let me know and I can arrange for copies. : Wish you success with your project. : W. Grandia P.E. : President QMI Inc.