ASTM D5389-93(2007)
(Test Method)Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
SIGNIFICANCE AND USE
This test method is used where high accuracy of velocity or continuous discharge measurement over a long period of time is required and other test methods of measurement are not feasible due to low velocities in the channel, variable stage-discharge relations, complex stage-discharge relations, or the presence of marine traffic. It has the additional advantages of requiring no moving parts, introducing no head loss, and providing virtually instantaneous readings (1 to 100 readings per second).
The test method may require a relatively large amount of site work and survey effort and is therefore most suitable for permanent or semi-permanent installations.
SCOPE
1.1 This test method covers the measurement of flow rate of water in open channels, streams, and closed conduits with a free water surface.
1.2 The test method covers the use of acoustic transmissions to measure the average water velocity along a line between one or more opposing sets of transducers-by the time difference or frequency difference techniques.
1.3 The values stated in SI units are to be regarded as the standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 6.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5389 − 93(Reapproved 2007)
Standard Test Method for
Open-Channel Flow Measurement by Acoustic Velocity
Meter Systems
This standard is issued under the fixed designation D5389; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions—For definitions of terms used in this test
1.1 This test method covers the measurement of flow rate of
method, refer to Terminology D1129.
water in open channels, streams, and closed conduits with a
free water surface.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acoustic path—the straight line between the centers of
1.2 Thetestmethodcoverstheuseofacoustictransmissions
two acoustic transducers.
tomeasuretheaveragewatervelocityalongalinebetweenone
or more opposing sets of transducers—by the time difference
3.2.2 acoustic path length—the face-to-face distance be-
or frequency difference techniques.
tween transducers on an acoustic path.
1.3 The values stated in SI units are to be regarded as the
3.2.3 acoustic transducer—a device that is used to generate
standard.
acoustic signals when driven by an electric voltage, and
conversely, a device that is used to generate an electric voltage
1.4 This standard does not purport to address all of the
when excited by an acoustic signal.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.2.4 acoustic travel time—the time required for an acoustic
priate safety and health practices and determine the applica-
signal to propagate along an acoustic path, either upstream or
bility of regulatory limitations prior to use. Specific precau-
downstream.
tionary statements are given in Section 6.
3.2.5 discharge—the rate of flow expressed in units of
volume of water per unit of time. The discharge includes any
2. Referenced Documents
sediment or other materials that may be dissolved or mixed
with it.
2.1 ASTM Standards:
D1129 Terminology Relating to Water
3.2.6 line velocity—the downstream component of water
D2777 Practice for Determination of Precision and Bias of
velocity averaged over an acoustic path.
Applicable Test Methods of Committee D19 on Water
3.2.7 measurement plane—the plane formed by two or more
D3858 Test Method for Open-Channel Flow Measurement
parallel acoustic paths of different elevations.
of Water by Velocity-Area Method
3.2.8 path velocity—the water velocity averaged over the
2.2 ISO Standard:
acoustic path.
ISO 6416 Liquid Flow Measurements in Open Channels—
Measurement of Discharge by the Ultrasonic (Acoustic)
3.2.9 stage—the height of a water surface above an estab-
Method lished (or arbitrary) datum plane; also gage height.
3.2.10 velocity sampling—means of obtaining line veloci-
ties in a measurement plane that are suitable for determining
This test method is under the jurisdiction of ASTM Committee D19 on Water
flow rate by a velocity-area integration.
and is the direct responsibility of Subcommittee D19.07 on Sediments,
Geomorphology, and Open-Channel Flow.
4. Summary of Test Method
Current edition approved June 15, 2007. Published July 2007. Originally
approved in 1993. Last previous edition approved in 2002 as D5389 – 93 (2002).
4.1 Acoustic velocity meter (AVM) systems, also known as
DOI: 10.1520/D5389-93R07.
ultrasonic velocity meter (UVM) systems, operate on the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
principle that the point-to-point upstream traveltime of an
Standards volume information, refer to the standard’s Document Summary page on
acoustic pulse is longer than the downstream traveltime and
the ASTM website.
that this difference in travel time can be accurately measured
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. by electronic devices.
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D5389 − 93 (2007)
FIG. 1 Velocity Component Used in Developing Travel-Time
Equations
4.2 Most commercial AVM systems that measure stream-
flow use the time-of-travel method to determine velocity along FIG. 2 Voltage Representation of Transmit and Receive Pulses at
Upstream and Downstream Transducers
an acoustic path set diagonal to the flow. This test method
describes the general formula for determining line velocity
defined as (Fig. 1 and Fig. 2):
1 1
necessary to provide water level (stage) and cross-sectional
B
t t
F G
CA AC
V 5 2 (1)
L
area information for calculation of the volume flow rate (see
2cosθ
Fig. 3).
where:
V = line velocity, or the average water velocity at the
L 5. Significance and Use
depth of the acoustic path,
5.1 Thistestmethodisusedwherehighaccuracyofvelocity
θ = angle of departure between streamflow and the acous-
or continuous discharge measurement over a long period of
tic path,
t
time is required and other test methods of measurement are not
AC = traveltime from A to C (upstream),
t
feasible due to low velocities in the channel, variable stage-
CA = traveltime from C to A (downstream), and
discharge relations, complex stage-discharge relations, or the
B = length of the acoustic path from A to C.
presence of marine traffic. It has the additional advantages of
4.3 The discharge measurement or volume flow rate deter-
requiring no moving parts, introducing no head loss, and
mination made with anAVM relies on a calibrated or theoreti-
providing virtually instantaneous readings (1 to 100 readings
cal relation between the line velocity as measured by theAVM
per second).
and mean velocity in the flow segment being measured.Taking
5.2 The test method may require a relatively large amount
morelinevelocitymeasurementsacrossthechannelatdifferent
of site work and survey effort and is therefore most suitable for
elevations in the acoustic plane and performing a numerical
permanent or semi-permanent installations.
integration or weighted summation of the measured velocities
and areas of flow can be used to better define the volume flow
6. Interferences
rate. The spacing between acoustic paths, the spacing between
thetoppathandtheliquidsurface,andthespacingbetweenthe
6.1 Refraction—Thepathtakenbyanacousticsignalwillbe
lowest path and the bottom are determined on the basis of
bent if the medium through which it is propagating varies
stream cross-section geometry or estimates of the vertical-
significantly in temperature or density. This condition, known
velocity distribution and by the required measurement accu-
as ray bending, is most severe in slow moving streams with
racy. In addition to several line velocity measurements, it is
poor vertical mixing or tidal (estuaries) with variable salinity.
In extreme conditions the signal may be lost. Examples of ray
bending are shown in Fig. 4. Beam deflection for various
temperatures and specific conductivities are shown in Fig. 5
Laenen, A., and Smith, W., “Acoustic Systems for the Measurement of
Streamflow,” U.S. Geological Survey Water Supply Paper 2213, 1983. and Fig. 6.
D5389 − 93 (2007)
7. Apparatus
7.1 The instrumentation used to measure open-channel flow
by acoustic means consists of a complex and integrated
electronic system known as an acoustic velocity meter (AVM).
Three or four companies presently market AVM systems
suitable for measurement of open-channel flow. System con-
figurations range from simple single-path to complex-multi-
path systems. Internal computation, transmission, and record-
ing systems vary depending on local requirements. MostAVM
systemsmustincludethecapabilitytocomputeanacousticline
velocity from one or more path velocities together with stage
(waterlevel)andotherinformationrelatedtochannelgeometry
necessarytocalculateaflowrateperunitoftime,usuallycubic
3 3
millimetres per second (m /s) or cubic feet per second (ft /s).
7.1.1 Electronics Equipment—There are several methods
that are currently being used to implement the electro-acoustic
functions and mathematical manipulations required to obtain a
line-velocity measurement. Whatever method is used must
includeinternalautomaticmeansforcontinuouslycheckingthe
accuracy. In addition, provision must be included to prevent
erroneous readings during acoustic interruptions caused by
rivertraffic,aquaticlife,orgradualdegradationofcomponents.
7.1.2 Flow Readout Equipment—This equipment is func-
tionally separated into three subsystems. These subsystems
may or may not be physically separable but are discussed
separately for clarity.
7.1.3 Acoustic Tranceiver—This system generates, receives,
and measures the traveltimes of acoustic signals. The acoustic
signals travel between the various pairs of acoustic transducers
FIG. 3 Example of Acoustic Velocity/Flow Measuring System
and form the acoustic paths from which line velocities are
determined.
6.2 Reflection—Acoustic signals may be reflected by the
7.1.4 Processor—The processor performs the mathematical
water surface or streambed. Reflected signals can interfere operations required to calculate acoustic line velocities, makes
with, or cancel, signals propagated along the measurement
decisions about which acoustic paths should be used on the
plane. When thermal or density gradients are present, the basis of stage, performs error checking, calculates total volume
placement of transducers with respect to boundaries is most
flow rate, and totalizes volume flow.
critical. This condition is most critical in shallow streams. A
7.1.5 Display/Recorder—Generally, the output of the sys-
general rule of thumb to prevent reflection interference is to
tem is a display or a recorder, or both. The recorder normally
maintain a minimum stream depth to path length ratio of 1 to
includes calendar data, time, flow rate, stage, and any other
100 for path lengths greater than 50 m.
information deemed desirable, such as error messages. Equip-
ment of this type is often connected to other output devices,
6.3 Attenuation—Acoustic signals are attenuated by absorp-
such as telemetry equipment.
tion, spreading, or scattering. Absorption involves the conver-
sion of acoustic energy into heat. Spreading loss is signal
7.2 Acoustic Transducers—Transducers may be active (con-
weakening as it spreads outward geometrically from its source.
taining Transmitter and first stage of amplification) or passive
Scattering losses are the dominant attenuation factors in
(no amplification) depending on path length and presence of
streamflow applications. These losses are caused by air
electromagnetic interference EMI. Acoustic transducers must
bubbles,sediment,orotherparticleoraquaticmaterialspresent
be rigidly mounted in the channel wall or bottom. Means must
in the water column. Table 1 presents tolerable sediment
be provided for precise determination of acoustic path eleva-
concentrations.
tion, length, and angle to flow. The transducers and cabling
must be sufficiently rugged to withstand the handling and
6.4 Mechanical Obstructions—Marine growth or water-
operational environment into which they will be placed.
borne debris may build up on transducers or weed growth,
Additionally, provision shall be made for simple replacement
boats, or other channel obstructions may degrade propagation
of transducer or cable, or both, in the event of failure or
and timing of acoustic signals.
damage.
6.5 Electrical Obstructions—Nearby radio transmitters,
electrical machinery, faulty electrical insulators, or other 7.3 StageMeasuringDevice—Thereareseveralmethodsfor
sources of electromagnetic interference (EMI) can cause fail- measuring stage and inputting this information to the system.
ure or sporadic operation of AVMs. The actual method used depends on the particular installation
D5389 − 93 (2007)
FIG. 4 Signal Bending Caused by Different Density Gradients
NOTE 1—Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond the
beam width but at a weak level. In the shaded area the detection is so great that signals cannot be received directly for any transducer beam width.
FIG. 5 Beam Deflection From Linear Temperature Gradients for Different Path Lengths
requirements. Some examples include visual measurement/
manual keyboard entry, float/counterweight or bubbler systems
D5389 − 93 (2007)
NOTE 1—Transducer directivity or beam width determined at the 30-dB level of the transmitted signal pattern. The signal is propagated beyond the
beam width but at a weak level. In the shaded area the deflection is so great that signals cannot be received directly for any transducer beam width.
FIG. 6 Beam Deflection From Linear Conductivity Gradients for Different Path Lengths
TABLE 1 Estimates of Tolerable Sediment Concentrations for
AVM System Operation Based on Attenuation From Spherical
Spreading and From Scattering From the Most Critical Particle
Size
NOTE 1—Sediment concentrations in milligrams per litre.
Selected Path distance (m)
Transducer
Frequency
5 20 50 100 200 300 500 1000
(kHz)
1000 6300 1200 400 — — — — —
500 — 3500 1200 530 230 — — —
300 — 7900 2800 1300 560 350 — —
200 — 11 000 4000 1800 830 520 280 —
100 — — 10 000 4600 2200 1400 770 350
30 — — — — 8800 5700 3200 1500
with servo manometers connected to analog conversion equip-
ment or digital encoders, upward looking acoustic transducers,
or other electronic pressure sensors.
7.4 Power Supply—Several venders currently offer battery-
powdered AVMs as well as systems operating on 110 V ac
standard commercial electric power. Availability of electricity
should be considered during site evaluation prior to equipment
selection.
7.5 Cabling—All interconnected cabling to and from trans-
ducers shall be armored or protected, or both, to minimize
damage during installation and operation.
7.6 Responders—A responder is an electronic device that
receives an acoustic signal and then retransmits it back across
FIG. 7 Responder System
the stream after a predetermined time interval. A responder is
used where direct wire connection is impractical. A typical
responder system is shown in Fig. 7
9. Preparation of Apparatus
8. Sampling
9.1 Site Selections:
8.1 Sampling, as defined in Terminology D1129,isnot 9.1.1 Channel Geometry—The gaged site should be in a
applicable to this test method. section of channel that is st
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