ASTM D5089-95(1999)
(Test Method)Standard Test Method for Velocity Measurements of Water in Open Channels with Electromagnetic Current Meters
Standard Test Method for Velocity Measurements of Water in Open Channels with Electromagnetic Current Meters
SCOPE
1.1 This test method covers the use of single-axis or dual-axis electromagnetic current meters for the measurement of water velocities in open channels.
1.2 This test method covers only these components and appurtenances of portable open-channel current-meter systems, which are customarily required when an operator is in attendance.
1.3 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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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 5089 – 95 (Reapproved 1999)
Standard Test Method for
Velocity Measurements of Water in Open Channels with
Electromagnetic Current Meters
This standard is issued under the fixed designation D 5089; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope the requirement that the water velocity must be zero at the wall.
3.2.2 cosine response—the ability of a meter, placed at an
1.1 This test method covers the use of single-axis or
angle to the oncoming flow, to sense the component of velocity
dual-axis electromagnetic current meters for the measurement
parallel to its axis.
of water velocities in open channels.
3.2.3 turbulence—irregular condition of flow in which the
1.2 This test method covers only these components and
various quantities show a random variation with time and space
appurtenances of portable open-channel current-meter systems,
coordinates so that statistically distinct average values can be
which are customarily required when an operator is in atten-
discerned.
dance.
1.3 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 Electromagnetic liquid flow current meters are based on
responsibility of the user of this standard to establish appro-
the Faraday principle of electromagnetic induction, which
priate safety and health practices and determine the applica-
states that voltage is proportional not only to flow speed but
bility of regulatory limitations prior to use.
also to the magnetic flux density and the distance between
2. Referenced Documents electrodes. In the application of the electromagnetic liquid
current meter, a conductor (water) moving in a magnetic field
2.1 ASTM Standards:
2 (created from within the sensor) generates a voltage that is
D 1129 Terminology Relating to Water
proportional to the rate of flow of water through the magnetic
D 2777 Practice for Determination of Precision and Bias of
2 field. This variable voltage lies in a plane that is perpendicular
Applicable Methods of Committee D-19 on Water
to both the water velocity vector and the magnetic field vector
D 3858 Test Method for Open-Channel Flow Measurement
and is sensed by pairs of electrodes.
of Water by Velocity-Area Method
D 4409 Test Method for Velocity Measurements in Open
5. Significance and Use
Channels with Rotating-Element Current Meters
5.1 This test method is particularly used for measuring the
2.2 ISO Standards:
velocity at a point in an open channel as part of a velocity-area
ISO 3454 Liquid Flow Measurement in Open Channels—
3 traverse to determine the flowrate of water. To this end it
Sounding and Suspension Equipment
should be used in conjunction with Test Method D 3858. A
ISO 3455 Liquid Flow Measurement in Open Channels—
single axis probe with cosine response will suffice for most of
Calibration of Rotating Element Current Meters in
3 these applications.
Straight Open Tanks
5.2 This test method is also useful in applications where the
3. Terminology velocity itself (rather than a volumetric flowrate) is the desired
end product.
3.1 Definitions: For definitions of terms used in this test
method refer to Terminology D 1129.
6. Interferences
3.2 Definitions of Terms Specific to This Standard:
6.1 As with any intrusive flow measuring device, electro-
3.2.1 boundary layer—a relatively thin layer of viscous
magnetic current meter sensors may be fouled by pieces of
influence adjacent to the probe (or any solid) surface caused by
debris of the type that can cling to or wrap around the sensor
which could affect measurement accuracy, and sensors may be
This test method is under the jurisdiction of ASTM Committee D-19 on Water
damaged by heavy debris in very high velocity flow.
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
6.2 Electromechanical flow sensors can be affected by oil or
phology, and Open-Channel Flow.
Current edition approved Sept. 10, 1995. Published November 1995. Originally
other materials coating the sensor.
published as D 5089 – 90. Last previous edition D 5089 – 90.
6.3 Electromagnetic flow sensors can be affected by exter-
Annual Book of ASTM Standards, Vol 11.01.
nal electrical noise such as that caused by nearby heavy
“Measurement of Liquid Flow in Open Channels,” ISO Standards Handbook
16, 1983. Available from American National Standards Institute, 1430 Broadway,
electrical equipment, and by voltage gradients caused by
New York, NY 10018.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 5089
nearby galvanic corrosion, or nearby power lines. Cables and current meters intended for open-channel use shall be equipped
connectors should be properly shielded to reduce noise prob- with appropriate fittings for either rod mounting or cable
lems. suspension; but it is preferable that general purpose current
6.4 Although electromagnetic velocity meters are in prin- meters be adaptable to both types of suspension. The cable
ciple capable of measuring substantially lower velocities than should be adequate to support sounding weights and also be
rotating element current meters, measurement of near-zero properly electronically shielded to prevent interference with
velocities may be hampered by noisy output signals caused by operation of the meter or transmission of signals from meter to
spurious electrical and magnetic noise, by fouling, by zero- readout equipment, or both.
drift, and by calibration uncertainties. Where external electrical 7.2.2 The rating of a current meter may depend upon the
noise creates uncertainty in sensed velocities, the electromag- geometry of the suspension system in the immediate vicinity of
netic meter may not be the appropriate velocity instrument for the velocity sensor. Therefore, if the manufacturer does not
the site. furnish the suspension system with which the meter was
calibrated, he shall provide all specifications necessary for the
7. Apparatus
user to mount the meter in a manner consistent with its
7.1 Electromagnetic Current Meter:
calibration.
7.1.1 The current meter consists of an electromagnet to
7.2.3 Although “rod mounting” can describe any rigid
generate a magnetic field perpendicular to the flow to be
suspension, in this context it frequently refers to a rod held
measured, electrodes to sense the generated voltage, a housing
vertically against the channel bottom by an operator standing
or supporting structure, and a voltage readout. The sensor can
over a small channel (or wading in a larger channel). The
have either one pair of electrodes or two orthogonal pairs of
connection for rod mounting shall provide, in conjunction with
electrodes depending upon whether it is a single-axis or
the rod, rigidity and vibration-free performance at the highest
multi-axis instrument.
velocity claimed for the meter, and shall provide for adjustable
7.1.2 The current meter must have a self-contained power
sensor position (depth) along the rod. The rod diameter shall be
source for the electromagnet and for any other electrical
in the range of 0.5 to 1.0 in. (12.7 to 25.4 mm).
components. This power source must have sufficient duration
7.2.4 Although cable suspension can describe any flexible
for normal field-work requirements. The power cells shall be
mooring, in this context it frequently refers to a (nearly)
either rechargeable or readily replaceable by an operator in the
vertical cable which is weighted at its end and which can be
field.
winched to place the current sensor at any desired depth.
7.1.3 The readout may be either in terms of electrical units
Descriptions of and requirements for suspension equipment
or directly in velocity. If the former, the manufacturer must
appropriate for stream gaging are available in ISO 3454. This
supply convenient velocity conversion tables with the instru-
test method includes only those elements which directly affect
ment. Readouts may be either analog or digital with a readout
the current-meter performance.
capability of giving velocity accurate to 60.01 ft/s (0.305
7.2.4.1 The connection between the sensor and cable must
cm/s).
permit the sensor to assume its normal operational position.
7.1.4 Optionally the current meter system may include a
The sensor must be stable with respect to the flow and be able
chart recorder or other type of data recording, storage or
to maintain its proper attitude; this can be accomplished by
transmission device in parallel with the manual readout. One of
design of sensor shape, use of fins, or by other means. If
these options is required only if the current meter is to be used
detachable fins or other appurtenances are provided, the
unattended. Specifications for these devices are beyond the
manufacturer must provide calibrations both with and without
scope of this test method.
this equipment.
7.1.5 Optionally the current-meter system may include
7.2.4.2 The weight used in a cable-and-weight suspension
direction-sensing equipment. Specifications for this equipment
should be heavy enough to avoid excessive downstream
are beyond the scope of this test method.
deflection of the cable, particularly in deep and swift waters. If
7.1.6 The current meter shall include a means by which the
some deflection is unavoidable, tables for air-line and wet-line
user can check its internal operation. However, it is empha-
corrections are available. The weights should offer minimal
sized that checks of this type do not constitute full calibrations.
resistance to the flow and should be able to maintain a stable
7.1.7 All components of the current-meter system shall be
and level position. They should be so shaped and placed that
made of materials that have corrosion resistance consistent
the current meter is not affected by eddies shed by the weight,
with the intended application. Fabrication material must be
blockage, or other instabilities.
selected to preclude galvanic corrosion, which could create
7.2.4.3 It is preferable that the weight be mounted below the
electronic interference and degrade accuracy readings of the
current meter. This permits the weight to serve as a s
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