温室大棚外文文献

SmartInfraredTemperatureSensorsKeepingupwithcontinuouslyevolvingprocesstechnologiesisamajorchallengeforprocessengineers.Addtothatthedemandsofstayingcurrentwithrapidlyevolvingmethodsofmonitoringandcontrollingthoseprocesses,andtheassignmentcanbecomequiteintimidating.However,infrared(IR)temperaturesensormanufacturersaregivingusersthetoolstheyneedtomeetthesechallenges:thelatestcomputer-relatedhardware,software,andcommunicationsequipment,aswellasleading-edgedigitalcircuitry.Chiefamongthesetools,though,isthenextgenerationofIRthermometers—thesmartsensor.Today’snewsmartIRsensorsrepresentaunionoftworapidlyevolvingsciencesthatcombineIRtemperaturemeasurementwithhigh-speeddigitaltechnologiesusuallyassociatedwiththecomputer.Theseinstrumentsarecalledsmartsensorsbecausetheyincorporatemicroprocessorsprogrammedtoactastransceiversforbidirectional,serialcommunicationsbetweensensorsonthemanufacturingfloorandcomputersinthecontrolroom(seePhoto1).Andbecausethecircuitryissmaller,thesensorsaresmaller,simplifyinginstallationintightorawkwardareas.Integratingsmartsensorsintoneworexistingprocesscontrolsystemsoffersanimmediateadvantagetoprocesscontrolengineersintermsofprovidinganewlevelofsophisticationintemperaturemonitoringandcontrol.IntegratingSmartSensorsintoProcessLinesWhilethewidespreadimplementationofsmartIRsensorsisnew,IRtemperaturemeasurementhasbeensuccessfullyusedinprocessmonitoringandcontrolfordecades(seethesidebar,“HowInfraredTemperatureSensorsWork,”below).Inthepast,ifprocessengineersneededtochangeasensor’ssettings,theywouldhavetoeithershutdownthelinetoremovethesensorortrytomanuallyresetitinplace.Eithercoursecouldcausedelaysintheline,and,insomecases,beverydangerous.Upgradingasensorusuallyrequiredbuyinganewunit,calibratingittotheprocess,andinstallingitwhiletheprocesslinelayinactive.Forexample,someofthesensorsinawiregalvanizingplantusedtobemountedovervatsofmoltenlead,zinc,and/ormuriaticacidandaccessibleonlybyreachingoutoverthevatsfromacatwalk.Intheinterestsofsafety,theprocesslinewouldhavetobeshutdownforatleast24hourstocoolbeforechangingandupgradingasensor.Today,processengineerscanremotelyconfigure,monitor,address,upgrade,andmaintaintheirIRtemperaturesensors.SmartmodelswithbidirectionalRS-485orRS-232communicationscapabilitiessimplifyintegrationintoprocesscontrolsystems.Onceasensorisinstalledonaprocessline,engineerscantailorallitsparameterstofitchangingconditions—allfromaPCinthecontrolroom.If,forexample,theambienttemperaturefluctuates,ortheprocessitselfundergoeschangesintype,thickness,ortemperature,allaprocessengineerneedstodoiscustomizeorrestoresavedsettingsatacomputerterminal.Ifasmartsensorfailsduetohighambienttemperatureconditions,acutcable,orfailedcomponents,itsfail-safeconditionsengageautomatically.Thesensoractivatesanalarmtotriggerashutdown,preventingdamagetoproductandmachinery.Ifovensorcoolersfail,HIandLOalarmscanalsosignalthatthereisaproblemand/orshutdowntheline.ExtendingaSensor’sUsefulLifeForsmartsensorstobecompatiblewiththousandsofdifferenttypesofprocesses,theymustbefullycustomizable.BecausesmartsensorscontainEPROMs(erasableprogrammablereadonlymemory),userscanreprogramthemtomeettheirspecificprocessrequirementsusingfieldcalibration,diagnostics,and/orutilitysoftwarefromthesensormanufacturer.Anotherbenefitofowningasmartsensoristhatitsfirmware,thesoftwareembeddedinitschips,canbeupgradedviathecommunicationslinktorevisionsastheybecomeavailable—withoutremovingthesensorfromtheprocessline.Firmwareupgradesextendtheworkinglifeofasensorandcanactuallymakeasmartsensorsmarter.TheRaytekMarathonSeriesisafulllineof1-and2-colorratioIRthermometersthatcanbenetworkedwithupto32smartsensors.Availablemodelsincludebothintegratedunitsandfiber-opticsensorswithelectronicenclosuresthatcanbemountedawayfromhighambienttemperatures.(seePhoto1).Clickingonasensorwindowdisplaystheconfigurationsettingsforthatparticularsensor.TheWindowsgraphicalinterfaceisintuitiveandeasytouse.Intheconfigurationscreen,processengineerscanmonitorcurrentsensorsettings,adjustthemtomeettheirneeds,orresetthesensorbacktothefactorydefaults.AllthedisplayedinformationcomesfromthesensorbywayoftheRS-485orRS-232serialconnection.Thefirsttwocolumnsareforuserinput.Thethirdmonitorsthesensor’sparametersinrealtime.Someparameterscanbechangedthroughotherscreens,customprogramming,anddirectPC-to-sensorcommands.Parametersthatcanbechangedbyuserinputincludethefollowing:RelaycontactcanbesettoNO(normallyopen)orNC(normallyclosed).Relayfunctioncanbesettoalarmorsetpoint.TemperatureunitscanbechangedfromdegreesCelsiustodegreesFahrenheit,orviceversa.Displayandanalogoutputmodecanbechangedforsmartsensorsthathavecombinedone-andtwo-colorcapabilities.Laser(ifthesensorisequippedwithlaseraiming)canbeturnedonoroff.Milliampoutputsettingsandrangecanbeusedasautomaticprocesstriggersoralarms.Emissivity(forone-color)orslope(fortwo-color)ratiothermometersvaluescanbeset.Emissivityandslopevaluesforcommonmetalandnonmetalmaterials,andinstructionsonhowtodetermineemissivityandslope,areusuallyincludedwithsensors.Signalprocessingd