1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS ISO/TS 15768:2000 ICS
2、17.120.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Measurement of liquid velocity in open channels Design, selection and use of electromagnetic current metersThis British Standard, having been prepared under the direction of the Sector Committee for Materials and Chemic
3、als, was published under the authority of the Standards Committee and comes into effect on 15 December 2000 BSI 12-2000 ISBN 0 580 36797 5 BS ISO/TS 15768:2000 Amendments issued since publication Amd. No. Date Comments National foreword This British Standard reproduces verbatim ISO/TS 15768:2000 and
4、 implements it as the UK national standard. The UK participation in its preparation was entrusted by Technical Committee CPI/113, Hydrometry, to Subcommittee CPI/113/1, Velocity-area methods, which has the responsibility to: aid enquirers to understand the text; present to the responsible internatio
5、nal/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its s
6、ecretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Stand
7、ards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pag
8、es This document comprises a front cover, an inside front cover, the ISO/TS title page, pages ii to v, a blank page, pages 1 to 9 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.Referencenumber ISO/TS15768:2000(E) TECHNICAL SPECIFICAT
9、ION ISO/TS 15768 Firstedition 2000-07-01 Measurementofliquidvelocityinopen channelsDesign,selectionanduseof electromagneticcurrentmeters Mesuragedelavitessedesliquidesdanslescanauxdcouverts Conception,choixetutilisationdesdbitmtreslectromagntiquesISO/TS15768:2000(E) ii ISO/TS15768:2000(E)iii Content
10、s Page Foreword.iv Introduction.v 1 Scope1 2 Normativereference1 3 Termsanddefinitions.1 4 Unitsofmeasurement.1 5 Physicalcharacteristicsoftheelectromagneticcurrentmeter1 5.1 General1 5.2 Sensinghead2 5.3 Meansofsuspension3 5.4 Controlunit.4 5.5 Signalcable4 5.6 Energysource5 6 Useofelectromagneticc
11、urrentmeters.5 6.1 General5 6.2 Measurementproceduresusingelectromagneticcurrentmeters.6 6.3 Useofanelectromagneticcurrentmeterinpreferencetoarotatingelementmeter7 6.4 Practicalaspectsofusinganelectromagneticcurrentmetertodetermineflowinopen channelsusingthevelocityareamethod.7 6.5 Selection,careand
12、maintenanceofelectromagneticcurrentmeters.8 Bibliography9ISO/TS15768:2000(E) iv Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnical committees.Eac
13、hmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnical Commission(IEC)onallmat
14、tersofelectrotechnicalstandardization. InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3. ThemaintaskoftechnicalcommitteesistoprepareInternationalStandards.DraftInternationalStandardsadopted bythetechnicalcommitteesarecirculatedtothememberbodiesforvoting.Publi
15、cationasanInternational Standardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. Inothercircumstances,particularlywhenthereisanurgentmarketrequirementforsuchdocuments,atechnical committeemaydecidetopublishothertypesofnormativedocument: anISOPubliclyAvailableSpecification(ISO/PAS)represents
16、anagreementbetweentechnicalexpertsinan ISOworkinggroupandisacceptedforpublicationifitisapprovedbymorethan50%ofthemembersofthe parentcommitteecastingavote; anISOTechnicalSpecification(ISO/TS)representsanagreementbetweenthemembersofatechnical committeeandisacceptedforpublicationifitisapprovedby2/3ofth
17、emembersofthecommitteecastinga vote. AnISO/PASorISO/TSisreviewedeverythreeyearswithaviewtodecidingwhetheritcanbetransformedintoan InternationalStandard. AttentionisdrawntothepossibilitythatsomeoftheelementsofthisTechnicalSpecificationISO/TS15768maybe thesubjectofpatentrights.ISOshallnotbeheldrespons
18、ibleforidentifyinganyorallsuchpatentrights. ISO/TS15768waspreparedbyTechnicalCommitteeISO/TC113,Hydrometricdeterminations,Subcommittee SC1,Velocityareamethods.ISO/TS15768:2000(E)v Introduction ThepurposeofthisTechnicalSpecificationistohighlighttheparticularcharacteristicsofthetypical electromagnetic
19、currentmeterthatdistinguishitfromthetypicalrotatingelementcurrentmeter,andtoprovide guidancetousersoftheelectromagneticdevicethatwillallowinformedjudgementstobemaderegardingitslikely performanceattributesandlimitationsinoperationalsituations.TECHNICALSPECIFICATION ISO/TS15768:2000(E)1 Measurementofl
20、iquidvelocityinopenchannelsDesign, selectionanduseofelectromagneticcurrentmeters 1 Scope ThisTechnicalSpecificationgivesguidelinesforthedesign,selectionanduseofelectromagneticcurrentmeters usedtodeterminepointvelocityforthepurposeofmeasuringflowinanopenchannelusingthevelocityarea method. NOTE Theele
21、ctromagneticcurrentmeterisacceptableasadeviceformakingpointdeterminationsofvelocityforthe purposesofopenchannelflowdeterminationbythevelocityareamethod,usingthemultiplepointvelocitysamplingtechnique describedinISO748(seereference1intheBibliography). 2 Normativereference Thefollowingnormativedocument
22、containsprovisionswhich,throughreferenceinthistext,constituteprovisionsof thisTechnicalSpecification.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthese publicationsdonotapply.However,partiestoagreementsbasedonthisTechnicalSpecificationareencouragedto investigatethepossibilityofapplyi
23、ngthemostrecenteditionofthenormativedocumentindicatedbelow.For undatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIEC maintainregistersofcurrentlyvalidInternationalStandards. ISO772,HydrometricdeterminationsVocabularyandsymbols. 3 Termsanddefinitions Forthepurpo
24、sesofthisTechnicalSpecification,thetermsanddefinitionsgiveninISO772apply. 4 Unitsofmeasurement TheunitsofmeasurementusedinthisTechnicalSpecificationareSIunits. 5 Physicalcharacteristicsoftheelectromagneticcurrentmeter 5.1 General 5.1.1 Anelectromagneticcurrentmeterwillnormallycomprisethefollowingcom
25、ponents: a) asensinghead(sometimesreferredtoasa“probe“); b) ameansofsuspension; c) acontrolunit;ISO/TS15768:2000(E) 2 d) asignalcable(betweenthesensingheadandthecontrolunit); e) asourceofelectricalenergy. 5.1.2 Thesourceofelectricalenergywillnormallybeabatterypack,containedwithinthecontrolunit.Thesi
26、gnal cablewillgenerallycontainseparateconductorstoconveytheelectricalsignaloutputfromthesensingheadtothe controlunitandthesubsequentelectricalresponsefromthecontrolunitbacktothesensinghead. 5.1.3 Thesignalcablemayormaynotbedetachablefromthesensingheadorfromthecontrolunit.Thisfeature mayvarybetweende
27、vicesmadebydifferentmanufacturers.Sensingheadsmayvarysignificantlyinsizeand shape. 5.1.4 Mostdevicesarecapableofdistinguishingandindicatingflowpolarity,i.e.whetherthedirectionofflowis forwardorbackwardswithrespecttothereferenceaxisofthesensingheaditself.Somemanufacturersoffer variantsthatareabletode
28、termineandindicateflowdirectionwithrespecttoabsolutedirectionalreferencesin eitherorbothofthehorizontalorverticalplanes. 5.2Sensinghead 5.2.1 Thesensingheadgenerallyconsistsofastreamlinedsolidbody,withinwhichislocatedan electromagneticcoil(forgeneratingalocalelectromagneticfield).Italsocontainsoneor
29、morepairsofsensing electrodescapableofdetectingtheelectricalpotentialgeneratedbythemovementofwater(theelectrical conductor)throughthelocalelectromagneticfield. 5.2.2 Thesensingheadmayalsocontainoneormoreofthefollowing: a) signalconditioningand/oramplificationelectronics; b) communicationselectronics
30、. 5.2.3 Thesensingheadmaybeexpectedtobeconstructedinsuchamanner,andofsuchmaterials,asto preventtheingressofmoisture,underallconditionsofuseforwhichthedeviceisintended,toanyextentthat wouldinterferewiththedevicesreliableandaccurateoperation,andforthedurationofthedevicesintended workinglifetime. 5.2.4
31、 Eachpairofsensingelectrodespresent,generallyappearsatthesurfaceofthehead,atagivendistance apartinfunctiontothedetaileddesignofthedevice.Movementofwater(theconductor)throughthe electromagneticfield,generatedbythedevicesinternalcoil,causesanelectricalpotentialtobegenerated.This potentialmaybedetected
32、bytheelectrodes,andisproportionalto a) thestrengthofthefield, b) thesizeoftheconductor,and c) thespeedoftheconductorthroughthefield. 5.2.5 Thesizeoftheconductor(thebodyofwaterwhosemeanspeedisdetectedbythedevice)isafunctionof theshapeandextentofthefieldgeneratedbyelectricalstimulationofthecoilandtheo
33、rientationofthatfieldwith respecttothemeandirectionofflow.Themaximumpotentialisnormallygeneratedwhenthestraightline interceptingapairofsensingelectrodesisnormaltothemeandirectionofflow.Differentproprietarydevicesmay createdifferently-sizedelectromagneticfieldsand,hence,samplethespeedofdifferently-si
34、zedbodiesofwater. 5.2.6 Thestrengthandextentofthegeneratedelectromagneticfieldmaybeofparticularrelevancewhen sensingheadsaredeployedincloseproximitytotheair/waterinterfaceortothewater/channel-bedinterface. Devicecalibrationmaybeaffectediftheelectromagneticfieldproducedisinterruptedbyoneorother(orbot
35、h)of themechanismsdescribed.Wherethequestionisrelevant,guidanceshouldbesoughtfromthemanufactureror supplierofthedevicethatistobeused.ISO/TS15768:2000(E)3 5.2.7 Indevicevariantsequippedwithtwoormorepairsofsensingelectrodes,pairsarenormallydisposedin linesthataremutuallyperpendicular.Thus,inatwo-paird
36、evice,thestraightlinesinterceptingeachseparatepairof electrodes(orplanescontainingthosestraightlines)wouldthemselvesintersectatrightangles.Thetwopairs wouldnormallybedeployedinthehorizontalplane,andthedeviceasawholewouldtherebyberenderedcapable ofdeterminingandindicatingtrueflowdirectionrelativetoan
37、absolutedirectionaldatumalsointhehorizontal plane. 5.2.8 Inathree-pairdevice,thethirdpairofelectrodesarenormallyorientedatrightanglestotheplaneofthe othertwopairs,andtheoveralldevicecandetermineandindicatetheabsolutedirectionwithrespecttothevertical aswellasthehorizontal. 5.2.9 Indevicedesignsthatal
38、lowdisconnectionofthesensingheadfromthesignalcable,theconnectoris normallyfullywater-resistant,capableofwithstandingsubmergencetoadepthindicatedbythedevice manufacturersproductspecification.However,itmaybeaprohibitedtodisconnecttheheadwhilethedeviceis underpowerfromitscontrolunit.Furthermore,threade
39、dconnectorsmaybemadeofveryfinethreadpitch, requiringcarefulattentionwhendisconnectingorre-connectingtoavoidaccidentaldamagetothethread(i.e. “stripping”)thatmightrendertheconnectorinsecureornolongerwater-resistant.Itisalsoimportanttokeepsuch connectorsscrupulouslyclean. 5.2.10Foranyelectromagneticcur
40、rentmetertoperformsatisfactorily,thewaterinwhichitisdeployedneedsto beadequatelyconductive.Theminimumwaterconductivityatwhichameterperformstoitsspecificationmayvary betweendevicesmadebydifferentmanufacturers,orbetweendifferentgenericvariantsofthesamemanufacturer. Typicalminimumvaluesofwaterconductiv
41、ityatwhichelectromagneticcurrentmetersmayreasonablybe expectedtoperformtospecification,rangebetween30 Sand100 S,dependingupondevicemanufactureand, also,uponwatervelocity.Asageneralization,lowvelocityandlowconductivitymaynotcombinewelltodeliver adequatemeasurementperformanceinaspecificmeter. 5.2.11Su
42、rfacecontaminationofthesensingheadmayhaveaneffectuponadevicescalibrationbyalteringthe electricalconductingpropertiesofitselectrodes.Sensingheadsshouldbehandledaslittleaspossible,anditis soundoperationalpracticetowashthemcleanofsiltorotherwaterbornecontaminationimmediatelyafterevery use,andtocleanthe
43、mfreeofgrease(withasoftclothandamildnon-abrasivedetergent)immediatelybeforeuse. Ifanoilfilmislocatedonthewatersurface,amethodshouldbeprovidedforprotectingthesensingheadfrom beingcoatedwithoilduringinsertionintothewater.Forexample,aplasticbagcanbeplacedoverthesensing headandthenremovedunderwaterandun
44、dertheoilfilm.Itisrecommendedtofollowthemanufacturers operatinginstructionsoradvice,whenprovided,onthesubjectofprobeorheadcontamination. 5.2.12Thespecificcalibrationofadeviceisalsolikelytobeafunctionofthehydrodynamiccharacteristicsofits sensinghead,asdeterminedbyitsspecificshape,andbythestateofsurfa
45、ceroughness.Sensingheadsare normallyconstructedfrommaterialthatisappropriatelyresistanttodamagebyimpact,abrasionorchemicalattack. Nevertheless,careshouldbetakeninthehandlinganddeploymentofthesensingheadofanelectromagnetic currentmetertopreventaccidentaldamagethataltersitsshapeorsmoothnessofitssurfac
46、efinishtoany significantdegree.Wherethereisdoubtastothesignificanceofanobservablealterationofthisnature,re- calibrationorcomparisonofperformanceagainstareferencedevicemaybeappropriate. 5.3Meansofsuspension 5.3.1 Thesensingheadofanelectromagneticcurrentmeterisnormallyconstructedtomakeitdeployableby e
47、asyattachmenttogaugingrodsasabasicmethodofsuspension.Itmayalsobepossibletosuspendsucha devicebycable,andtoattachatailfinandasinkerweighttoallowdeploymentincircumstanceswhererodsare notappropriate. 5.3.2 Dependinguponthespecificdesignofameteringsystem,thelengthofthesignalcablethatconnectsthe sensingh
48、eadwiththecontrolunitmaybelimited.Thecalibrationofaspecificindividualmetermaybeuniqueto thespecificlengthandtypeofsignalcableusedinthecourseofcalibration(seealso5.5.3). 5.3.3 Somemeterdesigns(butnotnecessarilyall),mayallowmeterdeploymentbymeansofacableway system.ISO/TS15768:2000(E) 4 5.4 Controlunit
49、 5.4.1 Dependinguponthespecificdesign,thecontrolunitofanelectromagneticcurrentmetershouldhaveorbe abletoperformsomeorallofthefollowingfeaturesorfunctions: a) switchthedeviceonandoff; b) containtherequiredbatterypowersupply; c) interfacewithanexternalsourceofcontinuously-availableelectricalenergy; d) re-chargeinternally-containedre-chargeablecells; e) applyappropriatelyregulatedelectricalstimulationtothesensinghead; f) detectaresponsesignalfromthesensingheadthatisrepresentativeoftheelectricalpotentialbeing generatedatanytimeacrossanindividualpairofsensingheadele
