ASTM D5089-95(2003)
(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
SIGNIFICANCE AND USE
This test method is particularly used for measuring the velocity at a point in an open channel 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. A single axis probe with cosine response will suffice for most of these applications.
This test method is also useful in applications where the velocity itself (rather than a volumetric flowrate) is the desired end product.
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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Designation:D5089–95(Reapproved2003)
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 3. Terminology
1.1 This test method covers the use of single-axis or 3.1 Definitions: For definitions of terms used in this test
dual-axis electromagnetic current meters for the measurement method refer to Terminology D 1129.
of water velocities in open channels. 3.2 Definitions of Terms Specific to This Standard:
1.2 This test method covers only these components and 3.2.1 boundary layer—a relatively thin layer of viscous
appurtenancesofportableopen-channelcurrent-metersystems, influence adjacent to the probe (or any solid) surface caused by
which are customarily required when an operator is in atten- therequirementthatthewatervelocitymustbezeroatthewall.
dance. 3.2.2 cosine response—the ability of a meter, placed at an
1.3 This standard does not purport to address all of the angle to the oncoming flow, to sense the component of velocity
safety concerns, if any, associated with its use. It is the parallel to its axis.
responsibility of the user of this standard to establish appro- 3.2.3 turbulence—irregular condition of flow in which the
priate safety and health practices and determine the applica- variousquantitiesshowarandomvariationwithtimeandspace
bility of regulatory limitations prior to use. coordinates so that statistically distinct average values can be
discerned.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
D 1129 Terminology Relating to Water 4.1 Electromagnetic liquid flow current meters are based on
D 2777 Practice for Determination of Precision and Bias of the Faraday principle of electromagnetic induction, which
Applicable Methods of Committee D19 on Water states that voltage is proportional not only to flow speed but
D 3858 Test Method for Open-Channel Flow Measurement also to the magnetic flux density and the distance between
of Water by Velocity-Area Method electrodes. In the application of the electromagnetic liquid
D 4409 Test Method for Velocity Measurements in Open current meter, a conductor (water) moving in a magnetic field
Channels with Rotating-Element Current Meters (created from within the sensor) generates a voltage that is
2.2 ISO Standards: proportional to the rate of flow of water through the magnetic
ISO 3454 Liquid Flow Measurement in Open Channels— field. This variable voltage lies in a plane that is perpendicular
Sounding and Suspension Equipment to both the water velocity vector and the magnetic field vector
ISO 3455 Liquid Flow Measurement in Open Channels— and is sensed by pairs of electrodes.
Calibration of Rotating Element Current Meters in
3 5. Significance and Use
Straight Open Tanks
5.1 This test method is particularly used for measuring the
velocity at a point in an open channel as part of a velocity-area
This test method is under the jurisdiction of ASTM Committee D19 on Water
traverse to determine the flowrate of water. To this end it
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
should be used in conjunction with Test Method D 3858.A
phology, and Open-Channel Flow.
single axis probe with cosine response will suffice for most of
Current edition approved June 10, 2003. Published August 2003. Originally
approved in 1990. Last previous edition approved in 1999 as D 5089 – 95 (1999).
these applications.
Annual Book of ASTM Standards, Vol 11.01.
5.2 This test method is also useful in applications where the
“Measurement of Liquid Flow in Open Channels,” ISO Standards Handbook
velocity itself (rather than a volumetric flowrate) is the desired
16, 1983.Available fromAmerican National Standards Institute, 25 W. 43rd St., 4th
floor, New York, NY 10036. end product.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5089–95 (2003)
6. Interferences 7.1.7 All components of the current-meter system shall be
made of materials that have corrosion resistance consistent
6.1 As with any intrusive flow measuring device, electro-
with the intended application. Fabrication material must be
magnetic current meter sensors may be fouled by pieces of
selected to preclude galvanic corrosion, which could create
debris of the type that can cling to or wrap around the sensor
electronic interference and degrade accuracy readings of the
which could affect measurement accuracy, and sensors may be
device.
damaged by heavy debris in very high velocity flow.
7.1.8 The manufacturer must inform the user of any limits
6.2 Electromechanical flow sensors can be affected by oil or
on ambient temperature, depth, velocity, or other parameters
other materials coating the sensor.
beyond which the instrument should not be used.
6.3 Electromagnetic flow sensors can be affected by exter-
7.2 Suspension:
nal electrical noise such as that caused by nearby heavy
electrical equipment, and by voltage gradients caused by 7.2.1 The current meter can be suspended in the channel
nearby galvanic corrosion, or nearby power lines. Cables and
either rigidly, referred to herein as rod mounting, or flexibly, as
connectors should be properly shielded to reduce noise prob- by cable and weight or other type of mooring. As a minimum,
lems.
current meters intended for open-channel use shall be equipped
with appropriate fittings for either rod mounting or cable
6.4 Although electromagnetic velocity meters are in prin-
suspension; but it is preferable that general purpose current
ciple capable of measuring substantially lower velocities than
meters be adaptable to both types of suspension. The cable
rotating element current meters, measurement of near-zero
should be adequate to support sounding weights and also be
velocities may be hampered by noisy output signals caused by
spurious electrical and magnetic noise, by fouling, by zero- properly electronically shielded to prevent interference with
operation of the meter or transmission of signals from meter to
drift,andbycalibrationuncertainties.Whereexternalelectrical
noise creates uncertainty in sensed velocities, the electromag- readout equipment, or both.
netic meter may not be the appropriate velocity instrument for
7.2.2 The rating of a current meter may depend upon the
the site.
geometryofthesuspensionsystemintheimmediatevicinityof
the velocity sensor. Therefore, if the manufacturer does not
7. Apparatus
furnish the suspension system with which the meter was
calibrated, he shall provide all specifications necessary for the
7.1 Electromagnetic Current Meter:
user to mount the meter in a manner consistent with its
7.1.1 The current meter consists of an electromagnet to
calibration.
generate a magnetic field perpendicular to the flow to be
7.2.3 Although “rod mounting” can describe any rigid
measured, electrodes to sense the generated voltage, a housing
suspension, in this context it frequently refers to a rod held
or supporting structure, and a voltage readout. The sensor can
vertically against the channel bottom by an operator standing
have either one pair of electrodes or two orthogonal pairs of
over a small channel (or wading in a larger channel). The
electrodes depending upon whether it is a single-axis or
connection for rod mounting shall provide, in conjunction with
multi-axis instrument.
the rod, rigidity and vibration-free performance at the highest
7.1.2 The current meter must have a self-contained power
velocity claimed for the meter, and shall provide for adjustable
source for the electromagnet and for any other electrical
sensorposition(depth)alongtherod.Theroddiametershallbe
components. This power source must have sufficient duration
in the range of 0.5 to 1.0 in. (12.7 to 25.4 mm).
for normal field-work requirements. The power cells shall be
either rechargeable or readily replaceable by an operator in the 7.2.4 Although cable suspension can describe any flexible
field. mooring, in this context it frequently refers to a (nearly)
vertical cable which is weighted at its end and which can be
7.1.3 The readout may be either in terms of electrical units
winched to place the current sensor at any desired depth.
or directly in velocity. If the former, the manufacturer must
Descriptions of and requirements for suspension equipment
supply convenient velocity conversion tables with the instru-
appropriate for stream gaging are available in ISO 3454. This
ment. Readouts may be either analog or digital with a readout
test method includes only those elements which directly affect
capability of giving velocity accurate to 60.01 ft/s (0.305
the current-meter performance.
cm/s).
7.1.4 Optionally the current meter system may include a 7.2.4.1 The connection between the sensor and cable must
chart recorder or other type of data recording, storage or permit the sensor to assume its normal operational position.
transmissiondeviceinparallelwiththemanualreadout.Oneof The sensor must be stable with respect to the flow and be able
these options is required only if the current meter is to be used
to maintain its proper attitude; this can be accomplished by
unattended. Specifications for these devices are beyond the design of sensor shape, use of fins, or by other means. If
scope of this test method.
detachable fins or other appurtenances are provided, the
manufacturer must provide calibrations both with and without
7.1.5 Optionally the current-meter system may include
this equipment.
direction-sensing equipment. Specifications for this equipment
are beyond the scope of this test method.
7.2.4.2 The weight used in a cable-and-weight suspension
7.1.6 The current meter shall include a means by which the should be heavy enough to avoid excessive downstream
user can check its internal operation. However, it is empha- deflection of the cable, particularly in deep and swift waters. If
sized that checks of this type do n
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