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1、Applicationofautomaticinstrumentinlandfillleachatetreatmentsystem2（自动化仪表在垃圾填埋场渗滤液处理系统中的应用2）Applicationofautomaticinstrumentinlandfillleachatetreatmentsystemsecondpages9ngns3.flowmeasurementFlowmeasurementisdividedintotwokinds.Oneisusedforflowmeasurementandtheotherisprocesscontrol,inorderto
2、improvethelevelofproductionautomation,improvetheprocessconditions,andimprovethequalityandoutputofproducts.Anotherkindofflowmeasurementisnotonlythemeasurementofleachatetreatment,butalsothebasisofcalculationofmajortechnicalandeconomicindicators.Amongthe8maineconomicindicatorsofwatersupplyent
3、erprises,3indicatorsarebasedondatameasuredbyflowmeters.Thefollowingfactorsshouldbetakenintoaccountintheselectionofflowmeters:(1)anytypeofflowmetermustbecertifiedbytheNationalMetrologyDepartmentbeforeitcanbeused.(2)thepressurelossoftheflowmeterissmall.(3)accordingtotherequirementsoftheindus
4、try,theaccuracyoftheflowmetershallbenolessthan2.5.(4)theinstallationsiteconditionsshallmeettherequirementsoftheselectedflowmeterforthestraightpipesection.(5)theselectedflowmetershallbeabletomeettheinstallationsiteenvironmentalconditions,suchastemperature,humidity,electromagneticinterferenc
5、e,etc..(6)theselectedflowmetershallbeapplicabletotheliquidmediumtobetested.Atpresent,theelectromagneticflowmeterandultrasonicflowmeterarethemostwidelyusedinengineeringdesign.A.electromagneticflowmeterTheprincipleofelectromagneticflowmeteristoapplyFala'selectromagneticinductionlaw,composedo
6、fsensorsandconverters.Inthemeasurement,theliquiditselfistheconductor,andthemagneticfieldisproducedbytwocoilsmountedinthepipe.ThecoilisexcitedbyalternatingcurrentorDCpower,andthemagneticfieldactsontheflowingfluidinthepipe.AvoltagecorrespondingtotheaveragevelocityVofthemeasuredfluidisgenerat
7、edinthepipeline,andthevoltageisindependentofthevelocitydistributionofthefluid.Twoelectrodesareinsulatedfromthepipetomonitortheinducedvoltageoftheliquid.Thedirectionofthemagneticfield,thedirectionoftheflowoffluidandtherelativepositionsofthetwodetectingelectrode
