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Appendix
MI 81
12Appendix
12.1DeterminationofEmissivity
Emissivity is a measure of an object’s ability to absorb and emit
infraredenergy.Itcanhaveavalue between0and1.0.Forexamplea
mirrorhas anemissivity of< 0.1,while theso‐called“Blackbody“
reachesanemissivityvalueof1.0.Ifahigherthanactualemissivity
value
is set, the output will read low, provided the target
temperatureisaboveitsambienttemperature.Forexample,ifyou
haveset0.95andtheactualemissivityis0.9,thetemperaturereading
willbelowerthanthetruetemperature.
An object’s emissivitycan be determined byone ofthe following
methods:
1. DeterminetheactualtemperatureofthematerialusinganRTD
(PT100), a thermocouple, or any other suitable contact
temperature method. Next, measurethe object’s temperature
and adjust emissivity setting until the correct temperature
valueisreached.Thisisthecorrectemissivityforthemeasured
material.
2. Forrelativelylow
temperatures(up to260°C/500°F)placea
plastic sticker (e.g. XXXRPMACED) on the object to be
measured. This stickershould be large enough to cover the
targetspot.Next,measurethesticker’stemperatureusingan
emissivitysettingof0.95.Finally,measurethetemperatureof
anadjacentareaonthe
objectandadjusttheemissivitysetting
until the same temperature is reached. This is the correct
emissivityforthemeasuredmaterial.
3. Ifpossible,applyflatblackpainttoaportionofthesurfaceof
theobject.Theemissivityofthepaintis0.95.Next,measurethe
temperatureofthepainted
areausinganemissivitysettingof