Upload
transcat
View
975
Download
0
Tags:
Embed Size (px)
Citation preview
1
The Infrared AdvantageThe Infrared AdvantageEmissivity and the Potential Impacts
on your Thermal Measurement
2
• What does it mean to measure temperature?
• Infrared Theory Review
• Emissivity Discussion
• Working with Emissivity to make Measurements
• Summary
AGENDA
3
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
4
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
5
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
6
•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
7
•Longer wavelengths than visible radiation, shorter than radio
•Travels through space at the speed of light
•Can be focused, reflected, refracted
INFRARED THEORY REVIEW
8
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
9
= 1.0= 1.0
100% emission100% emission
ɛɛ
==INFRARED THEORY REVIEW
Apparent Apparent TemperaturTemperatur
e e
Actual Actual TemperaturTemperatur
e e
10
Wabs
% transmission% transmission
INFRARED THEORY REVIEW
% emission% emission
% reflection% reflection
TOTAL
≠≠ Actual Actual TemperaturTemperatur
e e
< 1.0< 1.0ɛɛReflected Reflected Apparent Apparent
Temperature Temperature
Apparent Apparent TemperaturTemperatur
e e
11
WWabsabs
INFRARED THEORY REVIEW
25% reflection25% reflection
75% emission75% emission
Actual Actual TemperaturTemperatur
e e
Apparent Apparent TemperaturTemperatur
e e
Reflected Reflected Apparent Apparent
Temperature Temperature
TOTALTOTAL
= 0.75= 0.75ɛɛ
≠≠
12
INFRARED THEORY REVIEW
25% reflection25% reflection
75% emission75% emission
Actual Actual TemperaturTemperatur
ee40°C 40°C
Apparent Apparent TemperaturTemperatur
e e
Reflected Reflected Apparent Apparent
TemperatureTemperature0°C 0°C
>><< TOTALTOTAL
= 0.75= 0.75ɛɛ
1313
INFRARED THEORY REVIEW
25% reflection25% reflection
75% emission75% emission
Actual Actual TemperaturTemperatur
ee40°C 40°C
Apparent Apparent TemperaturTemperatur
e e
Reflected Reflected Apparent Apparent
TemperatureTemperature0°C 0°C
<< TOTALTOTAL
= 0.75= 0.75ɛɛ
1414
INFRARED THEORY REVIEW
25% reflection25% reflection
75% emission75% emission
Actual Actual TemperaturTemperatur
ee40°C 40°C
Apparent Apparent TemperaturTemperatur
e e
Reflected Reflected Apparent Apparent
TemperatureTemperature500°C 500°C
>><< TOTALTOTAL
= 0.75= 0.75ɛɛ
1515
INFRARED THEORY REVIEW
25% reflection25% reflection
75% emission75% emission
Actual Actual TemperaturTemperatur
ee40°C 40°C
Apparent Apparent TemperaturTemperatur
e e
Reflected Reflected Apparent Apparent
TemperatureTemperature500°C 500°C
>> TOTALTOTAL
= 0.75= 0.75ɛɛ
Emissivity
Emissivity
Emissivity can vary with:
•Material
Emissivity
Emissivity can vary with:
•Material
•Roughness
Emissivity
Emissivity can vary with:
•Material
•Roughness
•Wavelength
Emissivity
Emissivity can vary with:
•Material
•Roughness
•Wavelength
•Temperature
Emissivity
Emissivity can vary with:
•Material
•Roughness
•Wavelength
•Temperature
•Viewing angle
•Geometry
22
MEASUREMENT DEMONSTRATION
23
DEMONSTRATION
• FLIR T420 •Type K Thermocouple• Stainless Steel Cup• Scotch 3M Electrical Tape• Foot Powder Spray
Accurate analysis of low emissivity targets is
difficult…
Accurate analysis of low emissivity targets is
difficult…
Working with Emissivity
Accurate analysis of low emissivity targets is
difficult…
Accurate analysis of low emissivity targets is
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
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
27
(Demonstration)
Foot Powder Spray
Foot Powder Spray
3M Electrical
Tape
3M Electrical
Tape
Working with Emissivity
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.
28
29
ReflectedApparent
Temperature -
23.1°C
ReflectedApparent
Temperature -
23.1°C
(Demonstration)
Working with Emissivity
30
(Demonstration)
Working with Emissivity
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)
33
(Demonstration)
Working with Emissivity
Internal Temp -
51.9°CInternal Temp -
51.9°C
ROI Ɛ
Foot Powder .925
Stainless .099
3M Tape .953
34
Spot 1 Measures
97 degrees
Spot 2Measures
269 degrees?
Working with EmissivityGeometry
35
Working with EmissivityGeometry
36
Working with EmissivityGeometry
Working with EmissivityViewing Angle
Working with EmissivityEnvironment
Working with EmissivityEnvironment
40
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
46
Thanks