Understanding Infrared Thermography Reading 3

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Questions & Answers Subject: Answer this web queries from: http://www.thesnellgroup.com/community/ir-talk/f/9/p/1402/5433.aspx wonder if anyone can help me here. I am studying for my employer's Level 2 certification exam and I am using the ASNT supplement booklet to help. They ask a few question about IFOV and spot size calculation and I do not quite understand how they get the answers. basically it is not the answer I want but how they got to the answers. Question #1: A camera has an IFOV of 1.9 mRad. What is it's theoretical minimum spot size at a distance of 100 cm? Answer is: 0.19 cm (What formula is used for this and are there any units conversion like mm to cm or mRad to something else?) Question #2: The IFOV measurement of a radiometric system is 1.2 mRad. What is the maximum size object this system can accurately measure at a distance of 25 m? Answer is: 3 cm (now clearly there are unit conversions going on here from meters to cm. So how is it done?) Question #3: You are looking at an electrical connection 20 m in the air. What IFOV measurement is required to accurately measure the temperature on the 2.54 cm (1 in.) head of a bolt? Answer is: 1.25 mRad (I know it's just a matter of transposing the formula, but again there is units changes and I do not know the formula to apply) Last question: Using an IR system with an IFOV measurement ratio of 180:1. What is the smallest size object you can accurately measure at a distance of 3m (3.3 ft)? Answer is: 16.6 mm or (0.65 in). NOW this one I kind of figured out using: 1/180 = 0.0055 & 3 m = 3000mm therefore 0.0055 x 3000 = 16.5 Let me know if you all know how to do these problems. I think all I need is the formula and an understanding when and which units to convert. Charlie Chong/ Fion Zhang
Answer: D= σ•d, IFOV ration= 1/σ = d/D Question #1: A camera has an IFOV of 1.9 mRad. What is it's theoretical minimum spot size at a distance of 100 cm? Answer is: 0.19 cm (What formula is used for this and are there any units conversion like mm to cm or mRad to something else?) Calculation: D= 1.9 x 1 = 1.9mm or 0.19cm, (100cm = 1m) Question #2: The IFOV measurement of a radiometric system is 1.2 mRad. What is the maximum size object this system can accurately measure at a distance of 25 m? Answer is: 3 cm (now clearly there are unit conversions going on here from meters to cm. So how is it done?) Calculation: D= 1.2 x 25m = 30mm = 3cm Question #3: You are looking at an electrical connection 20 m in the air. What IFOV measurement is required to accurately measure the temperature on the 2.54 cm (1 in.) head of a bolt? Answer is: 1.25 mRad (I know it's just a matter of transposing the formula, but again there is units changes and I do not know the formula to apply) Calculation: 25.4 = σ x 20, σ = 1.27mRad Last question: Using an IR system with an IFOV measurement ratio of 180:1. What is the smallest size object you can accurately measure at a distance of 3m (3.3 ft)? Answer is: 16.6 mm or (0.65 in). Calculation: 1/ σ = d/D = 180, σ = 1/180, D = σ∙d, D = 1/180 x 3 = 0.01667m = 16.7mm (when calculating IFOV ratio, good to use the same unit for all inputs) 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
Page 169 and 170: Two-dimensional Scanning - Thermal
Page 171 and 172: Figure 3.5: Optomechanlcally scanne
Page 173 and 174: Pyroelectric Vidicon Thermal Imager
Page 175 and 176: Figure 3.6: Typical uncooled infrar
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Page 179 and 180: 3.6 Performance Parameters of Infra
Page 181 and 182: Performance parameters of qualitati
Page 183 and 184: Temperature Range Temperature range
Page 185 and 186: Temperature Sensitivity Temperature
Page 187 and 188: Speed of Response Speed of response
Page 189 and 190: Figure 3.7: Instrument speed to res
Page 191 and 192: Figure 3.8: Instrument field-of-vie
Page 193 and 194: D ≡ αd D = spot size (approximat
Page 195 and 196: Output Requirements Output requirem
Page 197 and 198: Spectral Range Spectral range denot
Page 199 and 200: Spectrall y selective instrumems us
Page 201 and 202: Figure 3.9: Spectral response of an
Page 203 and 204: 3.7 Performance Characteristics of
Page 205 and 206: The total field of view for a line
Page 207 and 208: Instantaneous Field of View IFOV In
Page 209 and 210: Recalling! Temperature sensitivity
Page 211 and 212: IFOV - MTF The 0.35 MTF refers to:
Page 213 and 214: Fig. 2a. Slit Response Function. Ca
Page 215 and 216: Minimum Resolvable Temperature Diff
Page 217 and 218: EXAM score! D=σ∙d IFOV ratio = d
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Page 239 and 240: Two-color Pyrometers or Ratio Pyrom
Page 245 and 246: 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
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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
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Platinum Silicide IrFPA 19 t«lU 98
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Quantitative IR Image Charlie Chong
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Quantitative Thermal Measurements S
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In addition to the spot measurement
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Stored images can be retrieved, dis
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Calibration Accessories Infrared ra
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Online printers and plotters are re
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Q1. The thermal resolution of an in
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Q7. The 3 to 5 μm spectral region
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Q13. A line scanner can be used to
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Q19. For which of the following app
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Q25. Two-color (ratio) pyrometers m
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Chapter 4 Operating Equipment and U
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■ Emissivity Differences ∆τ Em
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Causes of Real Temperature Changes
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Mass Transport Differences (Fluid F
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Figure 4.1: An indication of water
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Thermal Capacitance Differences ∆
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■ Induced Heating Differences (by
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Induced Heating Differences Charlie
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■ Energy Conversion Differences E
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Figure 4.3: Catalytic reformer vess
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Infrared Thermogram Energy Conversi
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Infrared Thermogram Energy Conversi
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■ Combination of Heat Transfer Me
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Infrared Thermogram of a running mo
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■ Spectral Considerations in Prod
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Infrared Thermogram Charlie Chong/
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Infrared Thermogram ..... " I Charl
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Figure 4.5: Spectral selectivity fo
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Figure 4.7: temperature thermogram
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Figure 4.8 shows the transmission s
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Figure 4.9: Measuring temperature o
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IR Filter Charlie Chong/ Fion Zhang
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Figure 4.10: Line scanner for conti
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Preparation of Equipment for Operat
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If the instrument is out of cal ibr
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The batteries mentioned on the miss
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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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