Understanding Infrared Thermography Reading 3

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■ Transmissivity Differences ∆τ Transmissivity differences can be caused by heat sources behind the target if the target is partly transparent in the infrared range. These will only be seen if the target transmissivity is high enough and the heat source is different enough in temperature from the target to contribute significantly to the total target radiosity. ■ Target Geometry Differences ∆D Target geometry differences are caused by multiple reflections within recesses or concavities on the target surface. They are actually variations in effective emissivity caused by changes in surface configurations. An example of this is the apparent temperature gradient in the far corner of an enclosure that is at a uniform temperature. Geometric differences diminish as target surface emissivity approaches unity. (blackbody does not affected by G) Charlie Chong/ Fion Zhang
Causes of Real Temperature Changes Real temperature changes may be caused by differcnces in mass transport (fluid flow), phase change (physical state). thermal capacitance, induced heating, energy conversion (friction. exothermic reactions and endothermic reactions), direct heat transfer by conduction, convection and radiation (thermal resistance) or a combination of two or more of these causes. ■ Mass Transport Differences (Fluid Flow) Mass transport differences are real temperatutc changes at the target surface caused by various forms of fluid flow. Free and forced convection are two examples of mass transport differences. Cool air exiting an air conditioning register will cause the register to become cooler. Hot water flowing within a pipe will cause the inside surface of the pipe to become warmer. (This will result in the outside of the pipe also becoming warmer.) Charlie Chong/ Fion Zhang
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Infrared Thermal Testing Reading II
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Infrared Thermography ~-- ... ... .
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Infrared Thermography Charlie Chong
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See Through & Fun Thermal Camera Ex
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How to see through clothing 2 I'
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Apache IR Thermal Weaponry ■ http
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Charlie Chong/ Fion Zhang
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Greek alphabet Letter Name Sound An
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Greek letter l fl 0 I1 p u w Charli
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SGuide-IRT Content Part 1 of 2 ■
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1.1 Introduction to Principles & Th
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The infrared thermal imaging equipm
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The three modes of heat transfer ar
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The three modes of heat transfer ar
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Temperature and Temperature Scales
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Boston Tea Party - New governances
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The Mighty Fahrenheit & ⅝”, Eng
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Absolute zero is equal to - 273.16
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The Fourier conduction Law expresse
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The Fourier conduction Law ( One di
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Convective Heat Transfer Convective
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Figure 1.2: Convective heat flow T
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Newton's cooling law defines the co
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Radiative Heat Transfer Radiative h
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Figure 1.4: Infrared radiation leav
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Thermal infrared radiation impingin
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Reflections off Specular and Diffus
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Reflections off Specular and Diffus
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Radiant Energy Related to Target Su
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The Stefan-Boltzmann law: W= σƐT
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Figure 1.6: Typical blackbody distr
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1.4 Practical Infrared Measurements
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Characteristics of the Target Surfa
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Referring back to Figure 1.5, the t
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Characteristics of the Transmitting
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Figure 1.10; Transmission of 10m (3
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Figure 1.11: Transmission, absorpti
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Figure 1.12: Transmission curves of
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Chapter 1 Review Questions Q&A 1. b
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Q4. Heat can only flow in the direc
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Q10. The follow ing spectral band i
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Q16. In forced convection, the boun
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Q22. In the 8 to 14 μm spectral re
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2.1 Materials Characteristics A kno
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For an emissivity reference table t
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Errors because of point source refl
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View Angle The angle between the in
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Thermal Conductivity Thermal conduc
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Thermal Diffusivity As in emissivit
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Partial 2.1 Table 2.1: d i'ffusivit
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Partial Table 2.2 Table 2.2: Normal
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Chapter 2 Review Questions Q&A 1. c
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4. When measuring the temperature o
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10. A highly textured surface is sa
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3.1 Thermal Instrumentation Overvie
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Thermopile- Thermoelectric Seebeck
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What is a IR Thermopile? (non-conta
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IR Thermopile Quad Sensor (non-cont
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Thermocouple A thermocouple is a te
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Bourdon Gas Thermometers 5 f\G.3 0
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Liquid Crystal Thermometer A liquid
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Bimetallic Thermometers Dial Spiral
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In RTD devices; Copper, Nickel and
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Platinum Resistance Thermometer Cha
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RTD Materials Different materials u
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Operations of RTD An RTD takes a me
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Benefits of Thin Film RTD There are
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Thermistor +V r===~ Op A p V to A I
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3.2 Contacting Thermal Measuring De
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■ Thermocouple Thermocouples are
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■ Thermistors Thermistors arc als
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3.3 Optical Pyrometers Optical pyro
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Pyrometer A pyrometer is a type of
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Brightness Pyrometers -Wien’s Law
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The processing electronics unit amp
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Infrared Detector An infrared detec
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Figure 3.2: Response Curves of Vari
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The mercury cadmium telluride (HgCd
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Infrared Optics - Lenses, Mirrors a
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Field of View (FOV) A field of view
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What is IFOV? A measure of the spat
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Instantaneous Field of View (IFOV)
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3.5 Scanning and Imaging When probl
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Line Scanning When the measurement
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Two-dimensional Scanning - Thermal
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Figure 3.5: Optomechanlcally scanne
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Pyroelectric Vidicon Thermal Imager
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Figure 3.6: Typical uncooled infrar
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IRFPA Charlie Chong/ Fion Zhang htt
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3.6 Performance Parameters of Infra
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Performance parameters of qualitati
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Temperature Range Temperature range
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Temperature Sensitivity Temperature
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Speed of Response Speed of response
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Figure 3.7: Instrument speed to res
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Figure 3.8: Instrument field-of-vie
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D ≡ αd D = spot size (approximat
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Output Requirements Output requirem
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Spectral Range Spectral range denot
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Spectrall y selective instrumems us
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Figure 3.9: Spectral response of an
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3.7 Performance Characteristics of
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The total field of view for a line
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Instantaneous Field of View IFOV In
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Recalling! Temperature sensitivity
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IFOV - MTF The 0.35 MTF refers to:
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Fig. 2a. Slit Response Function. Ca
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Minimum Resolvable Temperature Diff
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EXAM score! D=σ∙d IFOV ratio = d
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Charlie Chong/ Fion Zhang
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Answer: D= σ•d, IFOV ration= 1/
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Break Time - Kenya Coffee Picker Ch
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Portable Handheld Devices Charlie C
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Temperature sensitivity and readabi
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Hand Held Infrared Module Charlie C
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Note that the laser beam docs not r
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Emissivity set controls, located in
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IR Sensor Module Charlie Chong/ Fio
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IR Sensor Module Charlie Chong/ Fio
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Two-color Pyrometers or Ratio Pyrom
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Phenomena which are non-dynamic in
Page 247 and 248: Some ratio thermometers use more th
Page 249 and 250: Infrared Radiometric Microscopes Ch
Page 251 and 252: Line Scanners Line scanners are div
Page 253 and 254: Special Purpose Devices Special pur
Page 255 and 256: FLIR- Forward Looking Infrared Char
Page 257 and 258: Typically, the total field of view
Page 259 and 260: Pyroelectric devices have no direct
Page 261 and 262: Figure 3.12: Infrared focal plane a
Page 263 and 264: Infrared focal plane array imager C
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Page 267 and 268: On-board capabilities include isoth
Page 269 and 270: ccc Electron Microscope Image of mi
Page 271 and 272: Platinum Silicide IrFPA 19 t«lU 98
Page 273 and 274: Quantitative IR Image Charlie Chong
Page 275 and 276: Quantitative Thermal Measurements S
Page 277 and 278: In addition to the spot measurement
Page 279 and 280: Stored images can be retrieved, dis
Page 281 and 282: Calibration Accessories Infrared ra
Page 283 and 284: Online printers and plotters are re
Page 285 and 286: Q1. The thermal resolution of an in
Page 287 and 288: Q7. The 3 to 5 μm spectral region
Page 289 and 290: Q13. A line scanner can be used to
Page 291 and 292: Q19. For which of the following app
Page 293 and 294: Q25. Two-color (ratio) pyrometers m
Page 295 and 296: Chapter 4 Operating Equipment and U
Page 297: ■ Emissivity Differences ∆τ Em
Page 301 and 302: Mass Transport Differences (Fluid F
Page 303 and 304: Figure 4.1: An indication of water
Page 305 and 306: Thermal Capacitance Differences ∆
Page 307 and 308: ■ Induced Heating Differences (by
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Page 311 and 312: ■ Energy Conversion Differences E
Page 313 and 314: Figure 4.3: Catalytic reformer vess
Page 315 and 316: Infrared Thermogram Energy Conversi
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Page 319 and 320: ■ Combination of Heat Transfer Me
Page 321 and 322: Infrared Thermogram of a running mo
Page 323 and 324: ■ Spectral Considerations in Prod
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Page 327 and 328: Infrared Thermogram ..... " I Charl
Page 329 and 330: Figure 4.5: Spectral selectivity fo
Page 331 and 332: Figure 4.7: temperature thermogram
Page 333 and 334: Figure 4.8 shows the transmission s
Page 335 and 336: Figure 4.9: Measuring temperature o
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Page 339 and 340: Figure 4.10: Line scanner for conti
Page 341 and 342: Preparation of Equipment for Operat
Page 343 and 344: If the instrument is out of cal ibr
Page 345 and 346: The batteries mentioned on the miss
Page 347 and 348: Comments: ■ ■ ■ Thermal resol
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Figure 4.11 : Test configuration fo
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3. Reduce the ΔT until the image i
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■ Imaging Spatial Resolution Imag
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A sample setup is illustrated in Fi
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5. If the modulation transfer funct
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Figure 4.13: Test configuration for
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4. Open slit until V meas = V max .
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■ Learning the Startup Procedure
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■ Setting the Correct Effective E
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Figure 4.14: Test configuration for
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■ Measuring and Reporting Tempera
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■ Recognizing and Avoiding Reflec
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■ Measuring the Appropriate Backg
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■ Temperature Differences Between
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■ Liquid and Compressed Gases Som
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Dewar Flask for LN Loosely fitting
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■ Electrical Safety Failure to re
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Table 4.1: Electric shock current t
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4.4 Record Keeping Keeping thorough
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Easily accessible and easily unders
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Q1. Apparent but not real temperatu
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Q5. The higher the temperature of a
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Q9. Differential thermography can b
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5.1 Overview of Applications Becaus
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Electrical Applications Electrical
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High electrical resistance is the m
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Excessive heating due to a defectiv
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Inductive currents flowing with in
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Moisture in Airframes The detection
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Process Control and Product Monitor
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The differences produced by this co
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Night Vision, Seareh, Surveillance,
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Thermogram of helicopter taken at n
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Aircraft Under IR Trap Charlie Chon
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Instruments used for these applicat
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8 to 12 μm spectral region over wh
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Animal Studies Body heat allows inf
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Injured equine foreleg (left) appea
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Work energy is expended by friction
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5.4 Fluid Flow Investigations For s
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Figure 1.7: Thermographs of valve (
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■ Building Insulation and Other F
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Figures 5.8 and 5.9 illustrate thes
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Figure 5.9: Example of air exfiltra
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Example of air exfiltration Charlie
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■ Refractory Systems Industrial s
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Refractory Thermogram Charlie Chong
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■ Subsurface Discontinuity Detect
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Figure 5.11: An example of passive
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The equipment necessary to perform
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Figure 5.12: Example of active (hea
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Typical failure modes of the materi
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Figure 5.13: Test of aircraft deici
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DC - 9 Charlie Chong/ Fion Zhang
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Figure 5.14: Conceptual sketch of t
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In this case. however, the heat pul
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Figure 5.15: Erosion/corrosion dama
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737 aircraft Charlie Chong/ Fion Zh
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When there has been adequate solar
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Liquid Level Detection Thermal capa
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Unstimulated and Stimulated Approac
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Subsurface Discontinuity Detection
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1. A major area of infrared nondest
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5. The diagnostics involved in dete
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9. Thermography has been successful
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Appendix A Glossary The following a
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Ambient temperature - Temperature o
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Figure A-1 Apparent ambient tempera
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13.Blackbody, blackbody radiator -
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Alas! Heat Capacity Volumetric = C
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27.Detector, infrared - A transduce
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Thermal Effusivity In Thermodynamic
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Alas! Exitance = Rodiosity for my A
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45.Frame repetition rate - The time
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Thermal Inertia Thermal inertia is
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Instantaneous field of View (lFOV)
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Laser pyrometer - Laser pyrometer -
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Figure 3.2: Response Curves of Vari
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Compare: Minimum resolvable tempera
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86.Radiation rererenee source - A b
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101. Sector - For a line scanner, a
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113. Subtense, angular - The angula
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121. Thermal wave imaging - A term
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125. Thermogram - A thermal map or
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Appendix B Cost Benefit Determinati
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Although the calculations are quite
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96 ASNT Level Ill Study Guide: Infr
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Appendix C, Commonly Used Infrared
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Appendix C, Commonly Used Infrared
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Peach - 我爱桃子 Charlie Cho
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Good Luck Charlie Chong/ Fion Zhang
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Understanding Infrared Thermography Reading 3

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