System for measuring ultrasonically the elastic properties of a moving paper web

摘要

PCT No. PCT/SE95/01145 Sec. 371 Date Mar. 26, 1997 Sec. 102(e) Date Mar. 26, 1997 PCT Filed Oct. 5, 1995 PCT Pub. No. WO96/11396 PCT Pub. Date Apr. 18, 1996The invention relates to a system for measuring ultrasonically the elastic properties of a moving paper web. A noise type ultrasonic sound wave is generated by an ultrasonic sound generating device in the web at an excitation point. A reference ultrasonic wave reradiated into the air from the excitation point is indicated. A pick-up device is provided for receiving ultrasonic sound reradiated from the paper web at a predetermined distance form the location of the sound generating device. The ultrasonic sound generating device and the reference ultrasonic receiving device are provided on the same side of the paper web. At least one of these two kinds of devices includes a number of elements provided symmetrically in relation to the other device.