Extech Instruments LT40 User manual

USERMANUAL



WhiteLEDLightMeter



ModelLT40



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LT40-en-GB_V3.0 10/17

Introduction

CongratulationsonyourpurchaseoftheExtechLT40LEDLightMeterthatmeasureslightintensity

fromwhiteLEDlightsources.TheLT40canalsomeasurelightfromfluorescent,metalhalide,high‐

pressuresodium,andincandescentsources,forreferenceonly(unspecifiedaccuracy).TheLT40

canmeasurelightupto40,000Fc(400,000Lux).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:TheLCDwillshowOL.

LowbatteryIndication.

DisplayUpdateRate:2.5timespersecond.

CosineAnglecorrected.

MeasureswhiteLEDlight.

MeasurestheintensityofilluminationinLuxorfoot‐candles.

Dataholdfreezesdisplayedreading.

Maximum/Average/MinimumreadingHold.

ZeroCalibration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lowbatterysymbolappearsontheLCD.

Donottouchthemeter’scircuitboardforanyreason;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’).

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LT40-en-GB_V3.0 10/17

MeterDescription

1. Photodetector(removeprotectivecovertoexposesensor)

2. Display(LCD)

3. Controlpush‐buttons

4. PowerButton:ON/OFF



Batterycompartmentandtripodmountarelocatedon

rearofinstrument



Push‐ButtonDescription

1. Lux/Fcunitsselector

2. ZeroCalibrationbutton

3. Maximum/Average/Minimummemorybutton

4. Dataholdbutton

Operation

PowerON/OFF 

LongpressthePowerbuttontopowerthemeter.TopowerthemeterOFF,short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9999.However,forreadingsthatrepresent

measurementshigherthanthis,themeterusesx10orx100feature.Forexample,to

representameasurementof11,000fcthemeterwilldisplay1100withthex10indicator.

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LT40-en-GB_V3.0 10/17

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,longpressthePowerbutton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.

MAX/MINButton

Themetercanrecordthemaximum,minimum,andaveragereadingsasdescribedbelow:

1. Short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.

HOLDButton

PresstheHOLDbuttontofreezethecurrentreadingontheLCD.PresstheHOLDbuttonagainto

releasethereading.IntheDataHoldmode,HOLDisdisplayedontheLCD.

ZeroCalibrationProcedure

1. Ensurethattheprotectivecapisattachedtothelightsensor.

2. PowerthemeterandtheLCDshoulddisplay‘0’.

3. Shortpressthe“CALZERO”buttontoperformthezeroadjustment(CALwillappearonthe

display).

4. TheCALdisplaywillswitchoffwhenthecalibrationhasbeencompleted.

5. IftheprotectivecapisnotcoveringthesensorwhentheZero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-en-GB_V3.0 10/17

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.



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.



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.

1. Pressandholdthebatterycompartmentlockbutton(seediagram).

2. Slidethebatterycompartmentcoveroffinthedirectionofthe

arrow.

Installtwo(2)1.5V‘AAA’batteriesobservingcorrectpolarityandclose

thebatterycompartment.Ensurethatthecompartmentcoverissecurely

fastenedbeforeusingthemeter.



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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LT40-en-GB_V3.0 10/17

Specifications

UnitsRangeResolutionAccuracy

Lux



999.90.1WhiteLED:

±(3%reading+3Lux)upto500Lux

±(3%reading)>500Lux

Otherlightsources:Unspecified

9,9991

99,990*10

400,000*100

Foot

candles

99.990.01WhiteLED:

±(3%reading+0.3Fc)upto46Fc

±(3%reading)>46Fc

Otherlightsources:Unspecified

999.90.1

9,9991

40,000*10

*Readingsabove9999useax10orx100multiplier(1Fc=10.76Lux)

Angledeviationfromcosine

characteristics

30°±2%

60°±6%

80°±25%

GeneralSpecifications

Samplingrate2.5timespersecond(digitaldisplay)

PhotodetectorSiliconphoto‐diodewithcosinecorrection

Display4‐digitLCD(maximumdisplay:9999)withlowbatteryicon,

measurementoverload,andotherfunctionindicators

AutoRangeMeterautomaticallyrangesthedisplay

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

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0.9”)

Weight250g.(8.8oz.)includingbatteries

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LT40-en-GB_V3.0 10/17

Appendices

TypicalLightLevels(1Fc=10.76Lux)

LuxFoot

Candles

LuxFoot

Candles



 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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