Emissivity_Webinar_FLIR_Transcat_03252014

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The Infrared AdvantageThe Infrared AdvantageEmissivity and the Potential Impacts

on your Thermal Measurement

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• What does it mean to measure temperature?

• Infrared Theory Review

• Emissivity Discussion

• Working with Emissivity to make Measurements

• Summary

AGENDA

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HOW YOU MEASURE TEMPERATURE...

All temperature measuring devices accomplish this by measuring an effect of temperature:

•Thermistor: resistance changes with temperature

•Thermometer: volume changes with temperature

•Thermocouple: voltage changes with temperature

• IR Thermometers: voltage changes with temperature

• IR Camera: resistance changes with temperature

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1. Camera sensor pixels are heated by the incoming IR radiation.

2. The pixel resistance changes when heated.

3. The pixel resistance is measured and calibrated to a temperature value.

4. Temperature values are presented as an IR image.

HOW INFRARED CAMERAS WORK

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IR Cameras have several thousand measurement spots. A temperature measurement can be made from any of those spots in the IR image.

Like having up to 76,800 Like having up to 76,800 IR Thermometers or IR Thermometers or Thermocouples!Thermocouples!

INFRARED CAMERAS

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•Thermal excitation of molecules causes collisions•Collision energy is released as photons•Occurs at temperatures above absolute zero (-273.16⁰C, -459.72⁰F)

•Increases with temperature

•Heat transfer by the release of photons is known as thermal radiation (electromagnetic radiation).

INFRARED THEORY REVIEW

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•Longer wavelengths than visible radiation, shorter than radio

•Travels through space at the speed of light

•Can be focused, reflected, refracted


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The term “emissivity” is used to describe radiation efficiency of a target compared to a blackbody at the same wavelength, angle and temperature.

ɛ

Emissivity

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= 1.0= 1.0

100% emission100% emission

ɛɛ

==INFRARED THEORY REVIEW

Apparent Apparent TemperaturTemperatur

e e

Actual Actual TemperaturTemperatur

e e

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Wabs

% transmission% transmission


% emission% emission

% reflection% reflection

TOTAL

≠≠ Actual Actual TemperaturTemperatur

e e

< 1.0< 1.0ɛɛReflected Reflected Apparent Apparent

Temperature Temperature


e e

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WWabsabs


25% reflection25% reflection



e e


e e

Reflected Reflected Apparent Apparent

Temperature Temperature

TOTALTOTAL

= 0.75= 0.75ɛɛ

≠≠

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ee40°C 40°C


e e


TemperatureTemperature0°C 0°C

>><< TOTALTOTAL

= 0.75= 0.75ɛɛ

1313





ee40°C 40°C


e e



<< TOTALTOTAL

= 0.75= 0.75ɛɛ

1414





ee40°C 40°C


e e



>><< TOTALTOTAL

= 0.75= 0.75ɛɛ

1515





ee40°C 40°C


e e



>> TOTALTOTAL

= 0.75= 0.75ɛɛ

Emissivity

Emissivity

Emissivity can vary with:

•Material

Emissivity


•Material

•Roughness

Emissivity


•Material

•Roughness

•Wavelength

Emissivity


•Material

•Roughness

•Wavelength

•Temperature

Emissivity


•Material

•Roughness

•Wavelength

•Temperature

•Viewing angle

•Geometry

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MEASUREMENT DEMONSTRATION

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DEMONSTRATION

• FLIR T420 •Type K Thermocouple• Stainless Steel Cup• Scotch 3M Electrical Tape• Foot Powder Spray

Accurate analysis of low emissivity targets is

difficult…


difficult…

Working with Emissivity


difficult…


difficult…

But…there are ways to

compensate…

But…there are ways to

compensate…• Coatings• Surface Roughness •Geometry•Viewing Angle• Environment• Geometry• Subtraction


Working with Emissivity(Coatings)

TemporaryTemporary•Dye penetrant developer (welder supply)•Stick-on paper dots•White out (long wave)•Masking tape•Scotch 33 black vinyl electrical tape•Candle soot (small targets)•Contact paper

PermanentPermanent•Liquid Tape 1/16” •Plasti-dip 1/32”•Flat non-metallic paint •Scotch 70 silicone rubber•Bulldog #8 rubber (self adheres)•W.H. Brady Labels (stick-on)•Friction tape (self adheres)•Porcelain touchup enamel

Coatings with .95 EmissivityCoatings with .95 Emissivity

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(Demonstration)

Foot Powder Spray

Foot Powder Spray

3M Electrical

Tape

3M Electrical

Tape


Measuring Reflected Apparent Temperature

1. Place a sheet of crumpled Aluminum foil in front of your target

2. Set emissivity to 1.00, distance to 0

3. Measure the average temperature in a large area (box, circle, etc).

4. Enter the value into the software.

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ReflectedApparent

Temperature -

23.1°C

ReflectedApparent

Temperature -

23.1°C

(Demonstration)


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(Demonstration)


Internal Temp -

51.9°CInternal Temp -

51.9°C

ROI Result (ºC)

Foot Powder 50.0

Stainless 26.3

3M Tape 50.7

• Adjusts the emissivity of a Region of Interest (ROI / Analysis Tool), until the ROI temperature equals the actual temperature.

• Must know actual temperature of ROI.

• Must know Apparent Reflected Temperature.

• Does not change the appearance of the image.

Working with Emissivity(Software – Emissivity Adjustment)

• Adjusts the emissivity of a Region of Interest (ROI / Analysis Tool).

• Must know actual temperature of ROI.

• Must know Apparent Reflected Temperature.

• Does not change the appearance of the image.

Working with Emissivity(Software – Emissivity Calculator)

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(Demonstration)


Internal Temp -

51.9°CInternal Temp -

51.9°C

ROI Ɛ

Foot Powder .925

Stainless .099

3M Tape .953

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Spot 1 Measures

97 degrees

Spot 2Measures

269 degrees?

Working with EmissivityGeometry

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Working with EmissivityViewing Angle

Working with EmissivityEnvironment

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SUMMARY

• Importance of understanding Emissivity

• Knowing the Apparent Reflected Temperature

• Emissivity varies• Coatings, Surface Roughness,

Camera/ Software, Viewing Angle, Environment, and Geometry.

• IR Cameras Eliminate the Guesswork

• ASNT Training

So What Camera is Right for You

Ex Series T SeriesExx Series

Questions you Should Ask

• How far from the target?

• How hot is the target?

• What other applications?

• How often will you use the camera?

• What camera features do I need?

• Who will use the camera or cameras?

• What type of reporting and trending will I do?

• Radiometric JPEG image storage

• MSX Technology

• Fixed Focus (focus free)

• 3” Color LCD

• -20° C to 250° C Temperature Range

• Cost $995 to $5,995

FLIR Ex Series – Spot Gun Replacement

FLIR Exx-Series- Performance Cameras

• Large Touch screen

• Wi-Fi and Bluetooth for remote

reporting

• MSX Technology

• Laser, video light

• Accessory Lenses, wide angle,

telephoto

• Temp ranges up to 650° C

• Cost $3,995 to $7,995

FLIR T Series- High Performance

• Ergonomics/Outdoor

Applications

• High Temperature, up to

2,000° C

• High Resolution up to (640 x

480)

• Remote Controls

• $8,750 to $26,950

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Thanks

Emissivity_Webinar_FLIR_Transcat_03252014

Education

Transcript of Emissivity_Webinar_FLIR_Transcat_03252014