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TakexAmericaIncTrainingManual
IndustrialAutomationGroup
Rayman
Rev1.0
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Tableofcontents1) SensingTechnology...............................................................................................................................3
2) PhotoelectricSensor..............................................................................................................................5
a) Basiccomponentsofphotosensor
b) Photoelectricsensormodesofdetection.......................................................................................6
c) Photoelectricselectionsensorquestion........................................................................................6
d) PhotoelectricsensorTypes.............................................................................................................7
i) ThrubeamSensors...................................................................................................................7
ii) Diffuse.......................................................................................................................................9
iii) BackgroundSuppression........................................................................................................10
iv) Convergent.............................................................................................................................11
v) Reflex......................................................................................................................................12
vi) PolarizedReflex......................................................................................................................14
vii) Fiberoptics............................................................................................................................15
viii) Laser........................................................................................................................................16
ix) Color.......................................................................................................................................18
x) Mark........................................................................................................................................19
xi) ChemicalandOilresistant......................................................................................................21
3) UltrasonicSensor.................................................................................................................................22
4) LightCurtains…………………………………………………………………………………………………………………………………..23
5) HotandColdMetalSensor..................................................................................................................24
6) Terminology.........................................................................................................................................26
7) ApplicationTable.................................................................................................................................31
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1.SensingTechnologyinIndustrialAutomationAsensorcanbethoughtofasanautomaticswitch.Sensorshavecontributedsignificantlytorecentadvancesinmanufacturingtechnology.Usingasensormakesaprocessorsystemmoreautomatedandremovestheneedforahumanoperatorinterventiontomonitorandcontrolthesituation.Inallthemajorindustrialdetectionapplications,sensorsareusedfordetectingpresence,absenceordistanceofpartsfromoratareferencepoint.Theobjecttobedetectedisreferredtoasatarget.Whenatargetisdetectedthefunctionofthesensoristochangeoutputwhichinturnwillturnaloadorturnofftheload.Applicationsofdetectionsensorareasfollows:
1. Verifyingtheparthavereachedacertainposition2. Countingparts3. Verifyingproperplacementofpartsinthesystem4. Makingsureedgeofpartiswithinthespecifiedposition5. Determiningthesizeoftheproduct6. Verifyinglevelofliquidormaterial
Thethreemaincategoriesofsensorsusedinindustrialautomationarelimitswitches,proximityswitches(Inductive,Capacitive,photoelectric)sensors,longdistancesensing(Photoelectric,ultrasonic)sensors.Limitswitchesuseamechanicalactuatorrequiringthesensortochangeitsoutputwhenobjectisphysicallytouchingtheswitch.Sensors,suchasphotoelectric,inductive,capacitive,andultrasonic,changetheoutputwhenobjectispresent,butnottouchingthesensor.Inadditiontotheadvantagesanddisadvantagesofeach,sensortechnologyhasbeenwellsuitedforcertainapplications.Thetableonnextpageelaboratesthedifferenceofthesensortechnology.
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Sensor Advantages Disadvantages ApplicationLimitSwitches
• Highcurrentcapacity
• Lowcost• Lowtech
• Requiresphysicalcontact
• Veryslowresponse• Contactbounce• Wearandtear
• Interlocking• Basicendof
travel
Inductive
• Resistancetoharshenvironments
• Verypredictable• Longlife• Easytoinstall
• Shortdistanceupto50mm
• Machinetoolindustry
• Sensingmetalobjects
Capacitive
• Detectsobjectsinsidecontainer
• Candetectno-metallictargets
• Verysensitivetoextremeenvironmentalchanges
• Levelsensing
Photoelectric
• Sensesallkindsofmaterials
• Longlife• Longestsensingrange
• Veryfastresponsetime
• Lenssubjecttocontamination
• Sensingrangeaffectedbycolorandreflectivityoftargetobject
• Packaging• Material
handling• Partsdetection
Ultrasonic
• Sensesallmaterials • Resolution• Repeatability• Sensitivetotemperaturechanges
• Anti-collision• Doors• Web• Level
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2.PhotoelectricSensorsPhotoelectricSensors(PS)uselighttodetectthepresenceorabsenceofanobject.AllPhoto-sensorsconsistofthesensor,controlunit,andoutput.Thesourceisalightemittingdiodethatemitsapowerfulbeamofinfraredorvisiblelight.Thedetectoristypicallyaphotodiodethatsensesthepresenceorabsenceoflight.2a.BasiccomponentsofPhotoSensor: SourceLED Photodetector Lens(forsourceanddetector) PowerCircuit(modulatoranddemodulator) Amplifier OutputCircuit
Amplifier
Power Supply
Modulator
Source LED
Photodetector
Lens
Target or Reflector
Demodulator
OutputDetector Amplifier
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2b.PhotoSensormodesofdetection:
Thru-beam(Throughbeam)Reflex(Retro-reflective/Polarizedretro-reflective)Diffuse(Diffusereflective)
KEYPOINT CONSIDERATION
Range Howfaristheobjecttobedetected?Environment Howdirtyordarkistheenvironment?Accessibility Whataccessibilityistheretobothsidesoftheobjecttobe
detected?Wiring Iswiringpossibletooneorbothsidesoftheobject.Sizeandcolor Whatisthesizeandthecoloroftheobject?Consistency Istheobjectconsistentinsize,shape,andreflectivity?Requirements Whatarethemechanicalandelectricalrequirements?Outputsignal WhatkindofoutputisneededLogicfunction Arelogicfunctionsneededatthesensingpoint?Integration Isthesystemrequiredtobeintegrated?
2c.PhotoelectricSelectionquestions Thru-beam,Reflex DiffuseSensingObject 1. Sizeandshape
2. Transparency(opaque,translucent,ortransparent)
3. Speedinft/sorm/s(V)
1. Sizeandshape2. Color3. Material4. Surface(texturedorglossy)5. Speedinft/sorm/s(V)
Sensor 1. Sensingdistance(L)2. Restrictionofshapeorsize
a. Sensorb. Retro-reflector
3. Mountinga. Numberofsensorsb. mountingpitch
4. Limitationofinstallation
1. Sensingdistance(L)2. Restrictionofshapeandsize3. Mounting
a. Numberofsensorsb. Pitch
4. Limitationofinstallation
Background 1. Color2. Material3. Surface
Environment 1. Ambienttemperature2. Water,oilorchemicals
presence3. Other
1. Ambienttemperature2. Water,oilorchemicals
presence3. Other
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2d.PhotoelectricSensorTypes Thru-beamSensing
Thethru-beammethodrequiresthatthesourceanddetectorarepositionedoppositeeachotherandthelightbeamissentdirectlyfromsourcetodetector.Whenobjectpassesbetweentheemitterandreceiver,thebeamisbroken,signalingdetectionofobject.Thru-beamdetectiongenerallyprovidesthelongestrangeofthethreemodesandprovideshigherpoweratshorterrangetopenetratesteam,dirtorothercontaminantsbetweensourceanddetector.Alignmentofthesourceanddetectormustbeaccurate.Theeffectivebeamareaisthatofthecolumnoflightthattravelsstraightbetweenthelenses.Becausethelightfromsourcesistransmitteddirectlytophotodetector,thethru-beamsensingoffersthefollowingbenefit.
1. Longestrangeforsensing2. Highestpossiblesignalstrength3. Greatestlight/darkcontrastratio4. Besttrippointrepeatability
Limitation
1. Theyrequirewiringofthetwocomponentsacrossdetectionzone2. Itmaybedifficulttoalignsourceanddetector3. Iftheobjectdetectedissmallerthantheeffectivebeamdiameter,anapertureoverthelensmayberequired
Source DetectorObject
Effective beam
Thru-beamSensor
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Applicationexamples:
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DiffuseSensingThediffusemethodrequiresthatthesourceanddetectorareinstalledonthesamesideoftheobjecttobedetectedandaimedatapointinfrontofthesensor.Whenanobjectpassesinfrontofthesourceanddetector,lightfromthesourceisreflectedfromtheobjectsurfacebacktothedetector,andobjectisdetected.Ingeneral,throughbeamsensoroffersthegreatestranges,followedbyreflex,thendiffusesensors.Theoptimumrangeforthediffuseandreflexsensorismoresignificantthanthemaximumrange.Theoptimumrangeisbestshownbyanexcessgainchart.Thedetectingzoneiscontrolledbythetype,texture,andcompositionoftheobject.Advantagesofdiffusesensing:
1. Installationandalignmentaresimpleandinvolveswiringononeside.2. Itcandetectdifferenceinsurfacereflectivity
Limitation:
1. Ithaslimitedsensingrange2. Thelight/darkcontrastsensingrangedependsonthetargetobject’ssurfacereflectivity.
Applicationexample
Led
Photo-diode
detectionzone
Obj
ect
Diffuse Reflective type sensor
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BackgroundSuppressionBackgroundsuppressionenablesdiffusesensortohaveexcessgaintoapredeterminedlimitandinsufficientexcessgainbeyondthatrangewhereitmightpickupobjectsinmotionandyieldfalsedetection.Byusingtriangularranging,sensordevelopershavecreatedasensorthatemitslightthatreflectsbackonthedetectorfromtwodifferenttargetpositions.Thesignalreceivedfromthedistanttargetissubtractedfromtheclosertarget,providinghighexcessgainfortheclosertarget.
Lens
phot
o d
iode
Led
Background Suppression type sensor
obje
ct
back
grou
nd
Characteristicsofbackgroundsuppressionsensor:NotaffectedbyBackground Resistancetosoilingoflens Lessinfluencetocolor,shapeandmaterialofobjects
Applicationexamples:
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ConvergentSensingThisisaspecialvariationofdiffusesensing,whichusesadditionalopticstocreatesmall,intenseandwelldefinedimageatafixeddistanceinfrontofthesensorlens.Backgroundobjectswillnotfalsetriggeraconvergentreflectivesensorsincetheyarecross-eyedandcannotseepastacertainpoint.Convergentsensingisthefirstchoiceforsensingtransparentmaterialsthatremainwithinsensor’sdepthoffield.
LED
PHOTO DIODEDETECTION ZONE
Obj
ect
Obj
ect
obje
ct d
etec
ted
obje
ct n
ot d
etec
tedConvergent Reflective type sensor
ApplicationExample
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ReflexSensingThereflexmethodrequiresthatsourceanddetectorareinstalledatthesamesideoftheobjecttobedetected.Thelightbeamistransmittedfromthesourcetoaretro-reflectorthatreturnsthelighttodetector.Whenanobjectbreaksareflectedbeam,theobjectisdetected.Thereflexmethodiswidelyusedbecauseitisflexibleandeasytoinstallandprovidesbestcost-performanceratioofthreemethods.Theobjecttobedetectedmustbelessreflectivethanretroreflector.Sincethelighttravelsintwodirections(hencetwicethedistance),reflexsensorswillnotsenseasfarasthru-beamsensors.Howeverreflexsensorsofferapowerfulsensingsystemthatiseasytomountanddoesnotrequirethatelectricalwirebeingrunonbothsidesofthesensingarea.Themainlimitationofthesesensorsisthatashinysurfaceonthetargetobjectcantriggerfalsedetection.
Regular reflection (mirror)
Corner cube reflector reflectionRetroreflection
Diffuse reflection
Led
Photo-diode
Obj
ect
Retro-reflective Reflective type sensorRe
tro-re
flect
or
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Retro-reflectiveApplicationExample:
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PolarizedreflexPolarizedreflexsensorsuseapolarizingfilteroverthesourceanddetectorthatconditionsthelightsuchthatthephotoelectriccontrolseesonlylightreturnedfromthereflector.Apolarizedreflexsensorisusedinapplicationwhereshinysurfacessuchmetalorshrinkwrappedboxesmayfalsetriggerthecontrol.Polarizereflexsensingisachievedbycombiningsomeuniquepropertiesofpolarizerandretro-reflectors.Thepropertiesare,
1. Polarizerpasslightthatisalignedalongonlyoneplane2. Corner–cubereflectorsdepolarizelightasittravelsthroughthefaceoftheretro-reflector
Polarizedreflexsensorwillnotworkwithreflectivetapecontainingglassbeads.Also,shinyobjectwrappedwithclearplasticshrink-wrapwillpotentiallyfalsetriggerapolarizedreflexcontrol,sinceundercertainconditionstheseactascornercubereflector.Thepolarizedreflexsensorhasthefollowingadvantages:
1. Itisnotconfusedbythefirstsurfacereflectionsfromtargetobjects2. Ithasahighdark/lightcontrastratio3. Itiseasilyinstalledandaligned.Onesideofthesensingonlyneededbewired
Limitation:
1. Operatingrangeishalfthatofanon-polarizedsensorsincemuchofthesignalislostinthepolarizingfilters.2. Thesensorcanbefooledbyshinyobjectswrappedwithshrink-wrapmaterial.
Unpolarized light
Polarizing filter
Polarized light
Vertically polarized light
Horizontal polarizing filter
cannot pass vertical polarized light
Polarizing filterVertcally polarized light
Passess verticallypolarized light
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FiberOpticsSensingFiberopticssensorshavelargelybeenappliedtoapplicationinwhichtheirsmallsizehasmadethemconvenientreplacementforconventionalphotoelectricsensors.TheIndustryhassincediscoveredthattheprincipleoftotalinternalreflectionalsoappliestosmall-diameterglassandplasticfibersandthisleadtorapidgrowth.Becauseopticalfibersaresmallindiameterandflexible,theycanbendandtwistintoconfinedspaces.Alsobecausetheycontainnoelectronics,theycanoperateinmuchhighertemperatures-ashighas400˚Fandareasofhighvibration.Theyarelimitedbysensingdistances,whichtypicallyare80mmdiffusemodeandupto2000mminthru-beammode.Fiberopticscanleadtofalsedetectionbysmalldropofwaterordirt.Therearetwobasicsstylefiberopticassemblies,individualfiberopticsusedbyThru-beamsensorandbifurcatedfiberusedfordiffusedsensing.
Fiber optics sensor
Fiber optics cable
ApplicationExamples
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LaserSensorsLaserSensorsareespeciallysuitedforapplicationsthatrequirehighprecision.LaserSensorscombinethealignmentadvantagesofavisiblesensingbeamwiththeincreasedsensingrangeofalaser.TheyoperateClass1andClass2.ThesesensorsaccuratelydetectssmalltargetsandhavemuchlongersensingrangecomparedtostandardvisibleRedandinfraredsensors.Whenthelasersystemsareinstalled,itmustbeconsidered,e.g.bycorrectheightofinstallation,thatintentionaloraccidentallookingintothelaserbeamisprevented.Attheplaceofinstallationclearwarninglabelaretobeapplied.Additionalprotectivemeasuresanddetailedpersonnelinstructionsarenecessary.Theuseoftheunitsattheheightoftheheadorradiationindirectionswherepersonscanstayshouldbeavoided.Itisobviousthattheminimumdiameterofthelightspotisreachedatadefineddistance,thisdistanceisgiveninthedatasheetoftherespectiveunit.Thisdistanceisdeterminedbytheselectionoftheopticalelements.Itwouldbetoocomplicatedtomakethisdistancevariable.Letustakeananalogueexampleoutofthefieldofphotography.Ahighqualityzoomlensismuchmorecomplicatedandexpensivethanalenswith fixed focus.
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ColorSensors Colorsensordetectsthecolorofobjectswithoutmakingcontactbyhue,saturationandbrightness.Generally,itjudgeswhetherthecolorofanobjectisthesamewithregisteredcolor.Thesensorsemitlightandanalyzereflectionintothreecomponents(RED,GREENandBLUE)andidentifythecoloraccordingtotheproportionofthecomponents.TakexofferstwostyleofcolorsensorLEDandPassivecolorsensor.Typicalsensingdistance--13mm~33mm
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Applicationexamples:
MarkSensorsAmarksensordetectsthebrightnessandsaturationofcolorprintorpaintonobjectswithoutmakingcontactwiththeobject.Itismainlyusedonbagmakingmachines,automaticwrappingmachines,printingpresses,etc.forvarioustypesofcontrolsuchasdetectionofregistermarksinred,blue,yellow,etc.topositionforwrappingandcutting.Thereisabroadrangeofmarksensorswithdifferentapplicationsthatalsoincludedifferentiationbetweencolorswhereincorrectcolorsmaycausequalitycontrolproblemsandthedetectionofdifferentlevelsofreflectancebetweenpaintcolorsonthefrontandbacksidesofobjects(parts)inaproductionlinecheckingfortheincorrectsidefacingup.MarksensorshavecolorvariationoflightsourceLEDandU-shapedsensor.
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Applicationexamples
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OilandChemicalresistantsensors/SensorsforharshenvironmentPFseriessensorshaveaprotectivefluoro-plastic(PFA)coveringforenhancedresistancetooilsandchemicals.Thesearecapableforimmersedapplications.
ApplicationExample
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Someofthemodelshaveglasslenswhichcanwithstandharshenvironmentcomparedtooneswithaplasticlens.Thesesensorshaveahighpoweredlightbeamtosecurereliablelongrangedetectioneveninharshenvironments.
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3.UltrasonicSensorsUltrasonicsensorsdetectobjectsmadeofvariousmaterialsregardlessofshape,size,color,orsurfacecontours.Theyoperateusinghigh-frequency(100~500kHz)soundwavesthatareinaudibletohumanear.Thesesensorsworkwellinenvironmentscontainingdirt,mist,orvaporsthatcausedifficultyforphotoelectricsensors.Typicalsensingdistance--60mm~6m
ApplicationExamples
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4.LightCurtainsLightcurtainsreliablyandcost-effectivelyprotectagainstaccessintohazardouspointsandareas.Lightcurtainsarealsousedinapplicationtodetectfallingobjectfromaconveyor.TakexLightcurtainsaregoodforvariousapplicationsbutarenotsafetyrated.
Applicationexamples
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5.HotandColdMetalSensors TheHMD(HotMetalDetector)isusedforthedetectionofhotobjects.Todothis,thesensorusestheinfraredradiationthatisemittedbyhotmaterialswhichisreceivedbyanopticalsysteminthesensor.Ifthisradiationexceedsathresholdsetinthedevice(responsetemperature),thedeviceswitches.Thishappensextremelyfastandallowsthesafemonitoringofrapidprocesses.Responsetimesofupto5mscanbeachieved.Theprincipleoftheinfraredsensorallowsthedetectionofhotobjectsevenatagreatdistance.Infraredsensorsareusedwhereverinductivesensorscannotbemountedduetothehightemperature.TheCMD(ColdMetalDetector)iscomposedofthetransmitterandreceiverandhashighdetectionaccuracy.Itisusedeveniftheobjecttemperatureishighandunderstrongexternallight.Thepunchhalldetectionsensor(weldpointdetector)detectsthepunchhallinstalledintheweldingpartofthecoil(steelboard)thatrunscontinuouslybetweenthetransmitterandthereceiver.Typicalsensingdistance--250mm~1m
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ApplicationExamplesforHMD
ApplicationExampleforCMD
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6.TerminologyExcessGain:ExcessGainisameasureofsensingpoweravailableinexcessofthatrequiredtodetectanobject.Anexcessgainof1meansthereisjustenoughpowertodetectanobject,underbestconditionswithoutobstaclesplacedinthelightbeam.Thedistanceatwhichexcessgainequals1isthemaximumrange.Anexcessgainof100meansthereis100timesthepowerrequiredtodetectanobject.Generallymoreexcessgainavailableattherequiredrange,themoreconsistentlythecontrolwilloperate.Foreachdistancewithinrange,thereisspecificexcessgain.Throughbeamcontrolsgenerallyprovidethemostexcessgain,followedbyreflexanddiffuse.
TypicalExcessGainforThruBeamSensor
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TypicalExcessGainLongRangeDiffuse
TypicalExcessGainRetro-reflective
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TypicalExcessGainforBackgroundSuppression
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TypicalExcessGainforConvergentDiffuseSensor
BeamPatternA beam pattern is plotted on a 2-dimensional graph to illustrate how the photoelectric receiver is designed to respond to its emitter. Maximum light energy occurs along the sensor’s optical axis. The light energy decreases towards the beam pattern boundaries. The horizontal axis usually shows the range of the sensor.
Typical Beam Pattern for Thru-Beam sensor
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TypicalBeamPatternforDiffuseReflectivesensor
TypicalBeamPatternforRetroReflectivesensor
Contrastratio:Contrastmeasurestheabilityofphotoelectriccontroltodetectanobject,itisaratioofasignalstrengthwhendetectinganobject(light)toasignalstrengthwhenthere’snoobject(dark).Allotherbeingequal,thesensorthatprovidesthegreatestcontrastratioshouldbeselected.Forreliableoperationaratioof10:1isrecommended.
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7.ApplicationTable Selectionaccordingtoindustry
Sensor
Delivery/Logistics
Food
/packaging
/drug
Automated
machine
s
Robo
t
Semicon
ductor
Electron
icassem
bly
Stee
l/heavyIn
dustry
Textile
Chem
ical/oils
Pape
r/rubb
er/plastic
Glass/ceramic
Banking/service
Automob
ile
Fiberoptics
● ● ● ● ●
● ●
●
Embeddedamplifiersensor
● ● ● ● ● ●
● ● ● ● ● ●Lightcurtains ● ●
● ● ● ●
● ●
●
Backgroundsuppression ● ● ● ● ● ● ● ● ● ● ● ●UltrasonicSensors ● ● ● ● ● ● ● ● ●AC/DCPowersupplysensor
● ● ● ● ●MarkSensors ● ● ● ● ● ColorSensors ● ● ● ● ● ● ●ImageSensors ● ●
●
●
●
Photosensorforsteelandheavyindustries
●
●
Productspecific
● ●
● ●
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SelectionaccordingtopurposeofdetectionSensor
Turbidity
Distan
ce
Dimen
sion
Num
bero
frotations
Infrared
/tem
perature
Liqu
idlevel
Wafer
Glasss
ubstrate
Illum
inationche
ck
Ignitio
ncheck
Safety
Fiberoptics● ● ● ● ● ● ●
Embeddedamplifiersensor ● ● ● ● ● ● Lightcurtains
●
●Backgroundsuppression ● ● ● ● ● UltrasonicSensors
● ● ● AC/DCPowersupplysensor MarkSensors
● ● ● ColorSensors
ImageSensors
● ●
Photosensorforsteelandheavyindustries
●
Productspecific
● ●
● ● ● ● ●
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Selectionaccordingenvironment
Sensor
Restric
tedspace
High
/lowte
mpe
rature
Dusty
Subjecttowatersp
lash
Vacuum
Chem
ical
Explosiveen
vironm
ent
Fiberoptics● ● ● ● ●
Embeddedamplifiersensor ● ● ● ● Lightcurtains
Backgroundsuppression ● ● ● UltrasonicSensors
● ● AC/DCPowersupplysensor MarkSensors
ColorSensors
ImageSensors
Photosensorforsteelandheavyindustries
● ● ● Productspecific
● ● ●
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References:SensorHandbookbyDr.SabrineSolomanPhotoelectricSensors&Controls,selection&applicationMr.ScottJudsTakex2013Catalog