IRT25 User Manual

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EXTECHINSTRUMENTS

6IRT25‐en‐GB_V1.02/17

LocatingHotorColdSpots

Todetectahotorcoldspot,aimthethermometerataregionbeyondthetargetandthenscan

theentireregioninaslow,up/downmotion.

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DistancetoSpotRatio(FieldofView)

Themeter’s fieldof view is12:1(distance to spotratio). For example,ifthemeter is 24inches

fromthetarget(spot),thediameterofthetargetmustbeatleast2inches.Otherdistancesare

shownbelowinthefieldofviewdiagram.

Notethatmeasurementsshouldnormallybe

madecloserthan2feetfromthetarget.Themeter

canmeasurefromfurther distances but the measurementmaybeaffectedbyexternalsources

oflight.Inaddition,thespotsizemaybesolargethatitencompassessurfaceareasnotintended

tobemeasured.

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Itisnecessary to ensurethatthe size ofthe target islarger thanthespot size. Thesmaller the

target,thecloserthedistanceshouldbe.Seetheaccompanyingdiagram.

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Emissivity

Emissivityrepresents the energy reflectivity ofa material. Mostorganicmaterialsand painted

oroxidizedsurfaceshaveanemissivity ofapproximately0.95. If possible, masking tape or flat

blackpaintshouldbeappliedtocoverthemeasuredsurface.

Waitaperiodoftimetoallowthetapeorpainttoreach

thermalequilibriumwiththesurface

ofthecoveredobject.Measurethetemperatureofthesurfacecoveredwithtapeorpaintonly

afterequilibriumhasbeenachieved.

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User Manual - Page 6