ASTM D4409-95(2008)
(Test Method)Standard Test Method for Velocity Measurements of Water in Open Channels with Rotating Element Current Meters
Standard Test Method for Velocity Measurements of Water in Open Channels with Rotating Element Current Meters
SIGNIFICANCE AND USE
This test method describes the design and use of various types of current meters. These current meters are commonly used to measure the velocity at a point in an open channel cross section as part of a velocity-area traverse to determine the flowrate of water. To this end it should be used in conjunction with Test Method D 3858.
SCOPE
1.1 This test method describes the design and use of cup-type or vane-type vertical axis current meters and propeller-type horizontal axis current meters for measuring water velocities in open channels.
1.2 This test method is intended primarily for those meters customarily used in open-channel hydraulic (as distinguished from oceanographic) applications with an operator in attendance.
1.3 This test method is intended primarily for current meters that measure one component or filament of flow.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 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.
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Designation: D4409 − 95(Reapproved 2008)
Standard Test Method for
Velocity Measurements of Water in Open Channels with
Rotating Element Current Meters
This standard is issued under the fixed designation D4409; 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 ISO 3454 Liquid Flow Measurement in Open Channels—
Direct Depth Sounding and Suspension Equipment
1.1 This test method describes the design and use of
ISO 3455 Liquid Flow Measurement in Open Channels—
cup-type or vane-type vertical axis current meters and
Calibration of Rotating-Element Current Meters in
propeller-type horizontal axis current meters for measuring
Straight Open Tanks
water velocities in open channels.
1.2 This test method is intended primarily for those meters
3. Terminology
customarily used in open-channel hydraulic (as distinguished
3.1 Definitions: For definitions of other terms used in this
from oceanographic) applications with an operator in atten-
test method, refer to Terminology D1129.
dance.
3.2 Definitions of Terms Specific to This Standard:
1.3 Thistestmethodisintendedprimarilyforcurrentmeters
3.2.1 current meter—an instrument used to measure the
that measure one component or filament of flow.
speed or velocity of flowing water at a point.
1.4 The values stated in inch-pound units are to be regarded
3.2.2 Price-type current meters—generic name for specific
as standard. The values given in parentheses are mathematical
vertical axis meters with a rotating element consisting of six
conversions to SI units that are provided for information only
conical cups and constructed as described in Refs (1-3).
and are not considered standard.
1.5 This standard does not purport to address all of the
3.2.3 spin test— a test performed to check the bearings of a
safety concerns, if any, associated with its use. It is the current meter. This test is used primarily with vertical axis
responsibility of the user of this standard to establish appro-
current meters.
priate safety and health practices and determine the applica-
3.2.4 turbulence—irregular condition of flow in which the
bility of regulatory limitations prior to use.
velocity exhibits a random variation with time and space
coordinates so that statistically distinct average values can be
2. Referenced Documents
discerned.
2.1 ASTM Standards:
D1129 Terminology Relating to Water
4. Summary of Test Method
D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water 4.1 The angular velocity of the rotating element is a
function of water speed at the point of immersion.This angular
D3858 Test Method for Open-Channel Flow Measurement
of Water by Velocity-Area Method velocity is determined from the meter output and its functional
relation to the water speed is determined by calibration.
2.2 ISO Standards:
ISO 2537 Liquid Flow Measurement in Open Channels—
Rotating Element Current Meters 5. Significance and Use
5.1 This test method describes the design and use of various
This test method is under the jurisdiction of ASTM Committee D19 on Water
types of current meters. These current meters are commonly
and is the direct responsibility of Subcommittee D19.07 on Sediments,
usedtomeasurethevelocityatapointinanopenchannelcross
Geomorphology, and Open-Channel Flow.
Current edition approved Oct. 1, 2008. Published November 2008. Originally
section as part of a velocity-area traverse to determine the
approved in 1984. Last previous edition approved in 2003 as D4409 – 95 (2003).
flowrate of water. To this end it should be used in conjunction
DOI: 10.1520/D4409-95R08.
with Test Method D3858.
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
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., The boldface numbers refer to the list of references at the end of this test
4th Floor, New York, NY 10036, http://www.ansi.org. method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4409 − 95 (2008)
6. Interferences by magnetic, optical, or other methods, and shall produce a
signal which is audible, visible, or recordable by other means.
6.1 As with any intrusive flow measuring device, rotating
7.1.3.1 Amechanical-electriccontactdeviceshallnotaddin
element current meters are subject to damage by debris,
any significant manner to the internal friction at the lowest
especially in high velocity flows, and to fouling by floating
velocity claimed for the meter.
materials such as aquatic growths and sewage.
7.1.3.2 The contact device must always actuate the signal at
6.2 Owing to bearing friction, each rotating element current
precisely the same position in each revolution (fraction or
meter has a limiting low velocity below which it does not
multiple).
function reliably. This velocity is different for each type of
7.1.3.3 Iftherevolutioncountistobemademanuallybythe
meter but, in general, % errors tend to become large as the
operator, the audible or visual signals (as distinguished from
velocities decrease below 0.1 to 0.2 ft/s (0.03 to 0.06 m/s).
recorded signals) shall not occur at a frequency greater than 3,
and preferably 2.75, cps.
7. Apparatus
7.1.3.4 A timing device is a necessary adjunct to the meter
7.1 Current Meters—Rotating element current meters con-
so that the revolution rate can be determined from the
sist of a rotating element with shaft and bearings, a mechanism
revolution count. In the simplest configuration this system can
for detecting and registering revolutions, and a frame which
consist of a manual stopwatch for timing audible or visual
supportstheforegoingelementsandprovidesforsuspensionof
signals.
themeterandtheinsertionofstabilizingfinsifneeded.Current
7.1.3.5 If the current meter system has a direct readout in
meters covered by this test method do not customarily incor-
velocity units, the user must be furnished an accuracy state-
porate direction-measuring devices.
ment which includes the readout. Also, the user must be
7.1.1 Rotor Configuration—Horizontal-axis meters have
provided with a procedure to check for system malfunctions.
propeller-type rotors comprised of two or more blades. Inter-
7.1.4 Frame—The frame houses the current-meter elements
changeable elements of different pitch or diameter can be used
and provides for suspending the meter in the flow. Depending
to cover a wider range of velocities. Vertical-axis meters have
upon the intended use of the meter, the frame can be designed
a rotating wheel made up of several cup-type or vane-type
for suspension by rigid rod only, by cable-and-weight only, or
elements. Rotors employing six conical cups (for example,
it can provide for both types of suspension.
Price-type meters) are frequently used but other configurations
7.1.4.1 The connection for rod mounting shall provide, in
are permissible provided the following requirements are met:
conjunction with the rod, rigidity and vibration-free perfor-
7.1.1.1 The relation between velocity and rotation rate must
mance at the highest velocity claimed for the meter, and shall
be stable, that is, there should be no significant uncertainties in
provide for adjustable meter position along the rod. Fixed rod
the meter’s rating curve due to unstable flow separations at the
position is necessary for some applications, such as for
cups or similar hydrodynamic causes.
measuring through ice cover. Rods must be provided with
7.1.1.2 If fractions of revolutions are to be registered, the
suitable fixtures to accommodate fins as specified in 7.1.4.3.
angular movement of the rotor must be the same during each
7.1.4.2 Theconnectionforcablesuspensionshallpermitthe
measured fraction.
meter to swivel in a vertical plane so that it can seek and
7.1.2 Bearings:
maintain a horizontal orientation.
7.1.2.1 Bearing design shall permit the meter to be used in
7.1.4.3 Fins—Meterstobesuspendedbycablemustprovide
sediment-laden water, without affecting the accuracy of the
for stabilizing fins to be inserted into the frame. Provision shall
meter.
be made for balancing the meter-fin unit about its pivot while
7.1.2.2 If a particular oil is required for bearing lubrication,
immersed in water, so that it can operate in a level position at
thesuppliershallfurnishitwiththeinstrument.Informationfor
all velocities claimed for the meter.
obtaining replacement oil shall also be furnished.
7.1.5 Other General Requirements:
7.1.2.3 At the highest velocity claimed for the meter,
7.1.5.1 The meter design and construction shall be suffi-
properly maintained bearings shall function without adversely
ciently sturdy for normal field use and the materials shall be
affecting meter performance for a period of time customarily
usable in normally encountered fresh and saline waters without
associated with normal use or for the period of time between
undue corrosion or wear.
recommended recalibrations. If bearing replacement is needed
7.1.5.2 The meter shall offer low resistance to the flow and
to meet this requirement, such replacement shall be possible in
must be able to maintain a stable position with respect to the
the field.
flow.
7.1.2.4 At the lowest velocity claimed for the meter, prop-
erly maintained bearings shall function consistently and not 7.1.5.3 Meter parts shall be interchangeable among other
contribute to undue deviations in meter response. meters of the same model and manufacturer. The manufacturer
shall state which parts can be replaced without requiring
7.1.2.5 No breaking-in period for the bearings shall be
recalibration.
required after meter delivery.
7.1.3 Registering Revolutions—The current meter shall be 7.1.5.4 Design features which permit minor repairs or parts
equipped with a mechanism which detects and signals either replacement by the user in the field are encouraged. Any
single revolutions of the rotor or known fractions or multiples special purpose tools needed for such repairs or replacement
thereof. This detection can be by mechanical-electric contact, shall be furnished with the meter.
D4409 − 95 (2008)
7.1.5.5 For high-inertia, vertical-axis meters, spin test dura- where current meters are used to measure faster velocities,
tions shall be recommended for effective use of the meters at linear upward extension can be made with minimal accuracy
their lowest claimed velocity. See Refs (1-3) for Price-type degradation. Downward extrapolation may result in larger
meters. Users shall be provided with alternative procedures for errors, due to variable stall rates of individual meters. Provide
qualitative indications of internal friction in meters that are not theratingtotheuserintheformofanequation,table,orgraph.
amenable to spin testing. Furnish an estimate of the accuracy.
7.1.5.6 The user shall be provided with the means (detailed
9.1.2 Make individual calibrations, using the same suspen-
dimensions, templates, or forms) to ascertain gradual changes
sion with which the meter is to be used in the field. See 7.2.1
in rotor configuration, where appropriate. See also 10.2.
and 7.2.2.1.
7.1.5.7 Information on depth (pressure) limitation on meter
9.1.3 If a propeller meter is intended to respond only to the
submergence and on temperature effects, if any, on meter
velocity component along the meter axis, provide calibration
performance shall be furnished by the manufacturer.
information on this capability for the usable range of approach
angles claimed for the meter.
7.2 Suspension Equipment—Description and requirements
9.1.4 Recalibrate meters when their performance is suspect.
for suspension equipment are available in Refs (2, 3) and ISO
3454. This test method includes only those elements which Some organizations establish routine recalibration policies,
directly affect the meter performance. such as annually or based on hours of use. In the case of
7.2.1 Rods—The rod for which the meter rating is valid, if instruments made to stringent specifications, repairs and parts
not furnished with the meter, shall be precisely specified with replacement may be made without recalibration requirements.
regard to dimensions and configuration.
9.2 Towing Tank Calibration—Current meters usually are
7.2.2 Cable and Weight:
calibrated (rated) in a towing tank. Guidelines for this type of
7.2.2.1 The cable suspension system for which the meter
calibration are given in ISO 3455.
rating is valid, if not furnished with the meter, shall be
9.3 Water Tunnel Calibration—Current meters also can be
precisely specified with regard to dimensions and
calibrated in flowing water—in a facility that provides a
configuration,includingdimensionsofthesoundingweight,its
uniform velocity distribution in a test area large enough to
distance from the meter, connecting strap details, cable
avoid blockage effects, provided that the accuracy of the
dimensions, etc.
system is demonstrably high. If this procedure is used, provide
7.2.2.2 Theweightshallofferminimalresistancetotheflow
some indication of the scale and intensity of the turbulence.
and should be able to maintain a stable and level position. It
shall be so shaped that the current meter is not subject to shed
9.4 Group Ratings—Arating equation provided by a manu-
eddies or other instabilities; and it shall be heavy enough to
facturer for a specific type of current meter is sometimes used
avoid excessive downstream deflection of the cable, particu-
in place of an individual calibration equation.
larly in deep and swift currents. If some deflection is
9.4.1 Base group ratings can be made, based on individual
unavoidable, tables for air-line and wet-line corrections are
ratings of a significant number of meters with specified type of
available.
suspension (4). Preferably both new and well-maintained used
7.2.2.3 The suspension cable preferably shall be reverse-lay
meters should be included. Make the size, make-up, and
sounding cable to minimize torque on the immersed meter and
standard deviation of the sample known to the user.
weight. However, even this type of cable may cause or allow
9.4.2 A group rating pertains only to current meters manu-
meter yaw and subsequent meter registration errors for Price-
facturedinaspecificmanner.Anychangeinthemanufacturing
type current meters in velocities below 1.00 ft/s (0.305 m/s).
process requires reexamination of the group equation and
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