1、Designation:D508995(Reapproved 2014)Standard Test Method forVelocity Measurements of Water in Open Channels withElectromagnetic Current Meters1This standard is issued under the fixed designation D5089;the number immediately following the designation indicates the year oforiginal adoption or,in the c
2、ase of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the use of single-axis ordual-axis electromagnetic current meters for t
3、he measurementof water velocities in open channels.1.2 This test method covers only these components andappurtenances of portable open-channel current-meter systems,which are customarily required when an operator is in atten-dance.1.3 The values stated in inch-pound units are to be regardedas standa
4、rd.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard
5、 to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D1
6、9 on WaterD3858 Test Method for Open-Channel Flow Measurementof Water by Velocity-Area MethodD4409 Test Method for Velocity Measurements of Water inOpen Channels with Rotating Element Current Meters2.2 ISO Standards:3ISO 3454 Liquid Flow Measurement in Open ChannelsSounding and Suspension EquipmentI
7、SO 3455 Liquid Flow Measurement in Open ChannelsCalibration of Rotating Element Current Meters inStraight Open Tanks3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 boundary layera relativ
8、ely thin layer of viscousinfluence adjacent to the probe(or any solid)surface caused bythe requirement that the water velocity must be zero at the wall.3.2.2 cosine responsethe ability of a meter,placed at anangle to the oncoming flow,to sense the component of velocityparallel to its axis.3.2.3 turb
9、ulenceirregular condition of flow in which thevarious quantities show a random variation with time and spacecoordinates so that statistically distinct average values can bediscerned.4.Summary of Test Method4.1 Electromagnetic liquid flow current meters are based onthe Faraday principle of electromag
10、netic induction,whichstates that voltage is proportional not only to flow speed butalso to the magnetic flux density and the distance betweenelectrodes.In the application of the electromagnetic liquidcurrent meter,a conductor(water)moving in a magnetic field(created from within the sensor)generates
11、a voltage that isproportional to the rate of flow of water through the magneticfield.This variable voltage lies in a plane that is perpendicularto both the water velocity vector and the magnetic field vectorand is sensed by pairs of electrodes.5.Significance and Use5.1 This test method is particular
12、ly used for measuring thevelocity at a point in an open channel as part of a velocity-areatraverse to determine the flowrate of water.To this end itshould be used in conjunction with Test Method D3858.Asingle axis probe with cosine response will suffice for most ofthese applications.5.2 This test me
13、thod is also useful in applications where thevelocity itself(rather than a volumetric flowrate)is the desiredend product.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.07 on Sediments,Geomorphology,and Open-Channel Flow.
14、Current edition approved Jan.1,2014.Published March 2014.Originallyapproved in 1990.Last previous edition approved in 2008 as D5089 95(2008).DOI:10.1520/D5089-95R14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book o
15、f ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3“Measurement of Liquid Flow in Open Channels,”ISO Standards Handbook16,1983.Available fromAmerican National Standards Institute(ANSI),25 W.43rdSt.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyri
16、ght ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.Interferences6.1 As with any intrusive flow measuring device,electro-magnetic current meter sensors may be fouled by pieces ofdebris of the type that can cling to or wrap around the sensorwhich could affect measurement accuracy,and sensors may bedamaged by heavy debris in very high velocity flow.6.2 Electromechanical flow sensors can be affected by oil orother materials coating the sensor.6.
