Measuring and testing – Vibration – By mechanical waves
Patent
1995-01-30
1996-02-27
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
73598, 73639, 73159, G01N 2918
Patent
active
054939119
ABSTRACT:
A system for relatively accurately measuring the velocity and time of flight of ultrasonic signals in the thickness direction through moving web-like materials, such as paper, paperboard and the like, includes a pair of ultrasonic transducers disposed on opposing sides of the moving web-like material. The ultrasonic transducers are disposed in fluid-filled wheels to provide acoustical coupling between the transducers and the web-like material. In order to eliminate errors, known as trigger jitter, inherent in systems used to digitize ultrasonic signals for manipulation by a digital computer, a pulse echo box is provided to enable the capture of a reflected ultrasonic signal in addition to the ultrasonic signal transmitted through the web. By cross-correlating the transmitted and reflected ultrasonic signals in the same sample period, the error associated with trigger jitter is eliminated.
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Brodeur Pierre H.
Hall Maclin S.
Jackson Theodore G.
Ashraf Nashmiya
Institute of Paper Science and Technology, Inc.
Williams Hezron E.
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