Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels
Water-Resources Investigations Report
89-4090
Prepared in cooperation with the South Florida Water Management District
By: Antonius Laenen and R. E. Curtis Jr.
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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)
Suggested Citation
Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels; 1989; WRI; 89-4090; Laenen, Antonius; Curtis, R. E., Jr.
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Accuracy of acoustic velocity metering systems for measurement of low velocity in open channels |
| Series title | Water-Resources Investigations Report |
| Series number | 89-4090 |
| DOI | 10.3133/wri894090 |
| Year Published | 1989 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | Caribbean-Florida Water Science Center |
| Description | iii, 15 p. |
| Google Analytic Metrics | Metrics page |