Extech Instruments LT40 User manual

USERGUIDE
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WhiteLEDLightMeter
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ModelLT40
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LT40-EU-EN v1.3 9/13
2
Introduction
CongratulationsonyourpurchaseoftheExtechLT40LEDLightMeterthatmeasureslightfrom
whiteLEDlight,fluorescent,metalhalide,high‐pressuresodiumandincandescentsources.The
LT40canmeasurelightupto400,000Lux(40,000Fc).TheLT40offersanoverloadindication,low
batteryindication,Datahold,maximum/average/minimumhold(MAX/MIN),Zeroadjustment,
autopoweroffwithdisablefunction,andautorangingfeatures.Thisinstrumentisshippedfully
testedandcalibratedand,withproperuse,willprovideyearsofreliableservice.Pleasevisitour
website(www.extech.com)tocheckforthelatestversionofthisUserGuide,ProductUpdates,and
CustomerSupport.
Features
OverloadIndication:LCDscreenwillshow“OL”attheupperleft‐handcorner.
LowbatteryIndication””.
DisplayUpdateRate:2.5timespersecond.
SpectralresponsenearCIEluminousspectralefficiencyratings.
CosineAnglecorrected.
ConformstoJISC1609:1993andCNS5119generalclassASpecifications.
MeasuresLEDwhitelightandallvisiblelight.
MeasurestheintensityofilluminationinLuxorfoot‐candles.
Applicationsinclude:Warehouses,factories,officebuildings,restaurants,schools,library,
hospitals,photo/video,parkinggarages,museums,artgalleries,stadiums,building
security.
Dataholdfreezesdisplayedreading.
Maximum/Average/MinimumMemoryHold
Zeroadjustment.
Autopoweroffwithdisablefunction.
Autorange.
Safety
Donotoperatethemeterinenvironmentswherethefollowingarepresent:explosivegases
(ormaterials),combustiblegases(ormaterials),steam,ordust.
Pleasereplacethebatteryimmediatelywhenthesymbol“ ”appearsontheLCD.
Donottouchthemeter’scircuitboardforanyreasonasstaticelectricityorcontamination
coulddamagethesensitivecomponents.
ForIndooruseonly.Thisinstrumentwasdesignedforpollutiondegree2.
OperationAltitude:Upto2000m(7000’).

LT40-EU-EN v1.3 9/13
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MeterDescription
1. Photodetector(removeprotectivecovertoexposesensor)
2. Display(LCD)
3. Controlpush‐buttons
4. PowerButton:ON/OFF
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Batterycompartmentandtripodmountarelocatedon
rearofinstrument
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Push‐ButtonDescription
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1. Lux/Fcunitsselector
2. CalibrationandZERObutton
3. Maximum/Average/Minimummemorybutton
4. Dataholdbutton
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LT40-EU-EN v1.3 9/13
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Operation
PowerON‐OFF 
PressandholdthePowerbuttonforatleast2secondsandthenreleasetopowerthemeter.To
powerthemeterOFF,momentarilypressthePowerbutton.
TakingMeasurements
1. SwitchthemeterONandremovethesensor’sprotectivecovertoexposethelightsensor
dome.ThedisplayshouldswitchON,ifnotcheckthatbatteriesareinstalledandfresh.
2. Themetermeasurestheintensityofthelight(illuminance)thatstrikesthesensordomein
footcandlesandluxunits(1fc=10.76lux),displayingthismeasuredvalueonitsLCD.
3. Positionthemeterandlightsourcesothatthelightstrikesthesensordomestraighton
(perpendicular)withaslittleanangleaspossible.
4. Themeter’sdisplaycanshowavalueupto3999.However,forreadingsthatrepresent
measurementshigherthanthis,themeterusesx10feature(right‐mostdecimalpoint
flashing).Forexample,torepresentameasurementof39,999themeterwilldisplay3999
withtheright‐mostdigitflashing.
AutoPowerOFF
Tosavebatterylife,themeterpowersdownautomaticallyafterapproximately12minutesof
inactivity.
Enable/DisableAutoPowerOff
WhilethemeterisON,pressandholdthePowerbuttonforatleast2seconds(andthenrelease)
todisabletheAutoPowerOFFutility;theClocksymbolwillswitchOFF.ToenabletheAuto
PowerOFFutility,repeatthisprocess.
LUX/FCButton
PresstheLUX/FCbuttontotogglebetweenLuxandFC(foot‐candles)measurementunits.

LT40-EU-EN v1.3 9/13
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MAX/MINButton
Themetercanrecordthemaximum,minimum,andaveragereadingsasdescribedbelow:
1. Momentarilypressthe“MAX/MIN”buttonandthemeterwillbegintotrackthe
maximum/average/minimummeasurements;the“MAX”iconwilldisplayatthetopofthe
LCDwindowindicatingthatthemeterisnowshowingthemaximumreading.Thereading
willnotchangeuntilahigherreadingisregistered.
2. Pressthe“MAX/MIN”buttonagaintoswitchfrom“MAX”to“AVG”,wherethemeterwill
showtheaveragemeasurementvalue.The“AVG”iconwillbedisplayedabovethedisplayed
value.
3. Pressthe“MAX/MIN”buttonagaintochangethemodefrom“AVG”to“MIN”,wherethe
meterwillshowtheminimumvaluemeasured.The“MIN”iconwillbedisplayed.
4. Pressthe“MAX/MIN”buttonagaintoswitchfrom“MIN”backto“MAX”.
5. Toexitthismode,holdthe“MAX/MIN”buttonforatleast2seconds.TheMAX/AVG/MIN
iconsshouldallbeswitchedOFFwhentheunitreturnstothenormaloperatingmode.
Data‘Hold’Button
PresstheHOLDbuttontofreezesthecurrentreadingontheLCD.PresstheHOLDbuttonagain
toreleasethereading.
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CALIBRATIONandZEROButtons
1000LUXCalibration
1. Preparea2856oK/1000Luxlightsourceandfacethemeter’ssensorperpendicularly
towardthelightsource.
2. Simultaneouslypressandholdboththe“CAL/ZERO”buttonandthepowerbuttonforat
least2seconds.
3. Releasethebuttonswhen“CAL”isdisplayedontheLCDscreen.
4. Pressandholdthe“CAL”buttonfor2moreseconds,andtheLT40willpowerdown.
5. Themeterisnowcalibrated.
ZEROCalibration
1. Ensurethattheprotectivecoverisattachedtothelightsensor.
2. PowerthemeterandtheLCDshoulddisplay‘0’.
3. Momenarilypressthe“ZERO”buttonforthezeroadjustmentandtheCALiconwill
switchON.
4. TheCALiconwillswitchOFFwhenthecalibrationhasbeencompleted.
5. IftheprotectivecapisnotcoveringthesensorwhentheZEOcalibrationisstartedthe
LCDdisplaywillread“CAP”.Inthiscase,pleasecoverthesensorwiththecapandrestart
thisprocedure.
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LT40-EU-EN v1.3 9/13
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MeasurementConsiderationsandUserTips
Formaximumaccuracyallowthelightbeingmeasuredtofalldirectlyonthesensoras
perpendicularaspossiblewithaminimalangleofincidence.
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Whenthemeterisnotinusepleasekeeptheprotectivecapinplaceoverthelightsensor.
Thiswillprolongthelifeofthesensor.
Whenthemeteristobestoredforlongperiods,pleaseremovethebatteriesandstorethem
separately.Batteriescanleakandcausedamagetothemeter’scomponents.
Avoidareasofhightemperatureandhumiditywhenusingthisinstrument.
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BatteryReplacementandMaintenance
Cleaningandstorage
1. Thewhiteplasticsensordomeshouldbecleanedwithadampclothwhennecessary.Use
onlyamildsoapifneeded.Donotusesolvents,abrasives,orharshdetergentstocleanthe
dome.
2. Storethemeterinanareawithmoderatetemperatureandrelativehumidity.
BatteryReplacement
Whenthebatterypowerdecreasestoacriticallevel,thelowbatterysymbol“”willappearon
theLCD.Replacethe2x1.5VAAAbatterieslocatedintherearbatterycompartment.The
batterycompartmentslideseasilydownwardforremoval.Ensurethatthecompartmentcoveris
securelyfastenedbeforeusingthemeter.
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Neverdisposeofusedbatteriesorrechargeablebatteriesinhouseholdwaste.
Asconsumers,usersarelegallyrequiredtotakeusedbatteriestoappropriate
collectionsites,theretailstorewherethebatterieswerepurchased,orwherever
batteriesaresold.
Disposal:Donotdisposeofthisinstrumentinhouseholdwaste.Theuserisobligatedtotake
end‐of‐lifedevicestoadesignatedcollectionpointforthedisposalofelectricalandelectronic
equipment.
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BatterySafetyReminders
oPleasedisposeofbatteriesresponsibly;observelocal,state,nationalregulations.
oNeverdisposeofbatteriesinafire;batteriesmayexplodeorleak.
oNevermixbatterytypes;installnewbatteriesofthesametype.
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Specifications
Display4‐digitLCD(maximumdisplay:3999)withlowbatteryicon,
measurementoverload,andotherfunctionindicators
Sensor(detector)Siliconphotodiodewithspectralresponsefilterandcosine
correction
RangesandResolutionLux:399.9,3999,*39999,*399999
Foot‐candles:39.99,399.9,3999,*39999
*Readingsabove3999useax10orx100multiplier
(1Fc=10.76Lux)
Auto‐rangeThemeterautomaticallyrangesthedisplay
Accuracy±(3%ofreading+3digits)upto500Lux
±(3%)above500Lux
Calibratedtostandardincandescentlamp2856oKatan
ambienttemperatureof23oC
±8%forothervisiblelightsources
30±2%
60±6%
Angledeviationfromcosine
characteristics
80±25%
GeneralSpecifications
Samplingrate2.5timespersecond(digitaldisplay)
PhotodetectorSiliconphoto‐diodewithspectralresponsefilterandcosine
correction
OperatingconditionsTemperature:5to40oC(41to104oF);Humidity:<80%RH
StorageconditionsTemperature:‐10to60oC(14to140oF);Humidity:<70%RH
Lowbatteryindication“ ”appearsontheLCDwhenbatteryvoltagefallscriticallylow
LEDType WhiteLEDlightcanbeaccuratelymeasured
Powersupply2x1.5V‘AAA’batteries
BatterylifeApproximately200hours
AutoPowerOFFMeterswitchesOFFafter12minutesofinactivity
Dimensions133x48x23mm(5.2x1.9x1”)
Weight250g.(8.8oz.)includingbatteries

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Appendices
TypicalLightLevels(1Fc=10.76Lux)
LuxFoot
Candles
LuxFoot
Candles
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 Factories Home
20‐752‐7EmergencyStairs,Warehouse 100‐15010‐15Washing
75‐1507‐15Exit/EntrancePassages150‐20015‐20Recreational
Activities
150‐30015‐30PackingWork200‐30020‐30DrawingRoom,
Table
300‐75030‐75VisualWork:ProductionLine300‐50030‐50Makeup
750‐1,50075‐150Typesetting:InspectionWork500‐1,50050‐150Reading,Study
1,500‐3,000150‐300ElectronicAssembly,Drafting1,000‐2,000100‐200Sewing
 OfficeRestaurant
75‐1007‐10IndoorEmergencyStairs75‐1507‐15CorridorStairs
100‐20010‐20CorridorStairs150‐30015‐30Entrance,
WashRoom
200‐75020‐75Conference,
ReceptionRoom
300‐75030‐75CookingRoom,
DiningTable
750‐1,50075‐150ClericalWork750‐1,50075‐150ShowWindow
1,500‐2,000150‐2000Typing,Drafting
 StoreHospital
75‐1507‐15Indoors30‐753‐7EmergencyStairs
150‐20015‐20Corridor/Stairs75‐1007‐10Stairs
200‐30020‐30Reception100‐15010‐15SickRoom,
Warehouse
300‐50030‐50DisplayStand150‐20015‐20WaitingRoom
500‐75050‐75Elevator200‐75020‐75MedicalExamRoom
750‐1,50075‐150ShowWindow,
PackingTable
750‐1,50075‐150OperatingRoom
1,500‐3,000150‐300Storefront,ShowWindow5,000‐10,000 500‐1000EyeInspection
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SpectralSensitivity
Peaksensitivitywavelength:550nm;
Deviationfromcomparativeluminosity
standard:JISstandardC1609‐1993.
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RELATIVE SENSITIVITY (%)
WAVELENGTH (nm)
LT40