Understanding Infrared Thermography Reading 3

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■ Thermochromic Liquid Crystals Thermochromic liquid crystals (also called cholesterol crystals) change color with temperature. Coatings made of liquid crystals are commonly used as temperature threshold indicators. Depending on the mixture. a coating applied to a surface will change color predictably when the surface exceeds a threshold temperature. The color change may be reversible or irreversible. and the sensing range for most mixtures is limited to a narrow temperature span. Typically. a set of liquid crystal markers provides a selection of transition temperatures. This allows the user to select the appropriate marker for the desired temperature. Keywords: Threshold temperature Charlie Chong/ Fion Zhang
■ Thermocouple Thermocouples are contact temperature sensors based on the thermoelectric effect. or Seebeck effect. Thomas Seebeck discovered that, when two dissimilar metals arc joined at both ends and these ends are at different temperatures, a predictable direct current will flow through the circuit. The thermoelectric coefficient determines the relationship between this current and the temperature difference between the two junctions. This coefficient is known for each type of thermocouple. To configure a thermometer. the circuit is broken and the open-circuit voltage is measured by a volt meter. One of the two junctions is then held al a reference temperature. such as an ice bath, and the voltage is calibrated to indicate the temperature of the other junction. which then becomes the temperature sensing junction. Thermopiles arc banks of thermocouples connected in parallel or in series to increase output gradient. The reference temperature is important because of the thermocouples' non linear response. Keywords: thermoelectric coefficient 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
Page 87 and 88: 2.1 Materials Characteristics A kno
Page 89 and 90: For an emissivity reference table t
Page 91 and 92: Errors because of point source refl
Page 93 and 94: View Angle The angle between the in
Page 95 and 96: Thermal Conductivity Thermal conduc
Page 97 and 98: Thermal Diffusivity As in emissivit
Page 99 and 100: Partial 2.1 Table 2.1: d i'ffusivit
Page 101 and 102: Partial Table 2.2 Table 2.2: Normal
Page 103 and 104: Chapter 2 Review Questions Q&A 1. c
Page 105 and 106: 4. When measuring the temperature o
Page 107 and 108: 10. A highly textured surface is sa
Page 109 and 110: 3.1 Thermal Instrumentation Overvie
Page 111 and 112: Thermopile- Thermoelectric Seebeck
Page 113 and 114: What is a IR Thermopile? (non-conta
Page 115 and 116: IR Thermopile Quad Sensor (non-cont
Page 117 and 118: Thermocouple A thermocouple is a te
Page 119 and 120: Bourdon Gas Thermometers 5 f\G.3 0
Page 121 and 122: Liquid Crystal Thermometer A liquid
Page 123 and 124: Bimetallic Thermometers Dial Spiral
Page 125 and 126: In RTD devices; Copper, Nickel and
Page 127 and 128: Platinum Resistance Thermometer Cha
Page 129 and 130: RTD Materials Different materials u
Page 131 and 132: Operations of RTD An RTD takes a me
Page 133 and 134: Benefits of Thin Film RTD There are
Page 135 and 136: Thermistor +V r===~ Op A p V to A I
Page 137: 3.2 Contacting Thermal Measuring De
Page 141 and 142: ■ Thermistors Thermistors arc als
Page 143 and 144: 3.3 Optical Pyrometers Optical pyro
Page 145 and 146: Pyrometer A pyrometer is a type of
Page 147 and 148: Brightness Pyrometers -Wien’s Law
Page 149 and 150: The processing electronics unit amp
Page 151 and 152: Infrared Detector An infrared detec
Page 153 and 154: Figure 3.2: Response Curves of Vari
Page 155 and 156: The mercury cadmium telluride (HgCd
Page 157 and 158: Infrared Optics - Lenses, Mirrors a
Page 159 and 160: Field of View (FOV) A field of view
Page 161 and 162: What is IFOV? A measure of the spat
Page 163 and 164: Instantaneous Field of View (IFOV)
Page 165 and 166: 3.5 Scanning and Imaging When probl
Page 167 and 168: 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
Page 177 and 178: IRFPA Charlie Chong/ Fion Zhang htt
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
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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
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Some ratio thermometers use more th
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Infrared Radiometric Microscopes Ch
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Line Scanners Line scanners are div
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Special Purpose Devices Special pur
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FLIR- Forward Looking Infrared Char
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Typically, the total field of view
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Pyroelectric devices have no direct
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Figure 3.12: Infrared focal plane a
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Infrared focal plane array imager C
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Infrared focal plane array imager C
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On-board capabilities include isoth
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ccc Electron Microscope Image of mi
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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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