Abstract: | Acoustic velocity meter (AVM) accuracy depends on equipment limitations, the accuracy of acoustic-path length and angle determination, and the stability of the mean velocity to acoustic-path velocity relation. Equipment limitations depend on path length and angle, transducer frequency, timing oscillator frequency, and signal-detection scheme. Typically, the velocity error from this source is about +or-1 to +or-10 mms/sec. Error in acoustic-path angle or length will result in a proportional measurement bias. Typically, an angle error of one degree will result in a velocity error of 2%, and a path-length error of one meter in 100 meter will result in an error of 1%. Ray bending (signal refraction) depends on path length and density gradients present in the stream. Any deviation from a straight acoustic path between transducer will change the unique relation between path velocity and mean velocity. These deviations will then introduce error in the mean velocity computation. Typically, for a 200-meter path length, the resultant error is less than one percent, but for a 1,000 meter path length, the error can be greater than 10%. Recent laboratory and field tests have substantiated assumptions of equipment limitations. Tow-tank tests of an AVM system with a 4.69-meter path length yielded an average standard deviation error of 9.3 mms/sec, and the field tests of an AVM system with a 20.5-meter path length yielded an average standard deviation error of a 4 mms/sec. (USGS) |
Genre: | USGS Numbered Series |
ProdID: | 28197 |
Citation Author: | Laenen, Antonius; Curtis, R. E., Jr. |
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Citation Language: | ENGLISH |
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Citation Phsyical Description: | iv, 15 p. :ill. ;28 cm. |
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Citation Publisher: | U.S. Geological Survey, |
Citation Series: | Water-Resources Investigations Report |
Citation Series Code: | WRI |
Citation Series Number: | 89-4090 |
Citation Search Results Text: | Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels; 1989; WRI; 89-4090; Laenen, Antonius; Curtis, R. E., Jr. |
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Citation Year: | 1989 |
Type: | citation/reference |
Text: | Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels; 1989; WRI; 89-4090; Laenen, Antonius; Curtis, R. E., Jr. |
URL (THUMBNAIL): | http://pubs.usgs.gov/wri/1989/4090/report-thumb.jpg |
URL (INDEX PAGE): | http://sofia.usgs.gov/publications/wri/89-4090/ |
URL (DOCUMENT): | http://pubs.usgs.gov/wri/1989/4090/report.pdf |
Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
Publisher: | U.S. Geological Survey, |