Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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Can this be true? Is the metal cap only 103 ºF? No. You are seeing an example of the apparent temperature and the effect of emissivity. The fuse end cap is a highly reflective metal, in this case copper. Notice that the body of the fuse also appears hotter than the metal cap. The temperature of the cap is actually as hot as the fuse body it’s in contact with. To explain why the apparent temperature seen through a thermal imager can be significantly different than the actual temperature, let’s review our knowledge of physics. Charlie Chong/ Fion Zhang http://reliableplant.com/Read/14134/emissivity-underst-difference-between-apparent,-actual-ir-temps
Thermal radiation and properties of materials All objects emit infrared (thermal) radiation. The intensity of the radiation depends on the temperature and nature of the material’s surface. At lower temperatures, the majority of this thermal radiation is at longer wavelengths. As the object becomes hotter, the radiation intensity rapidly increases and the peak of the radiation shifts towards shorter wavelengths. The relationship between total radiation intensity (all wavelengths) and temperature is defined by the Stefan-Boltzmann Law: (broad band) Q = eσT 4 where: Q = radiation intensity e = emissivity of material σ = Stefan-Boltzmann constant T = absolute temperature Charlie Chong/ Fion Zhang http://reliableplant.com/Read/14134/emissivity-underst-difference-between-apparent,-actual-ir-temps
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Infrared Thermal Testing Reading VI
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6.1 Basic Elements An in-house prog
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6.1.4 Responsibilities This section
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IR Viewing Window - Opaque Polymer
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6.1.8 Acceptance Criteria All surve
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6.1.9 Reporting Criteria A rigid pr
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6.1.10 Qualification of Personnel P
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EPRI Licensed Material Basic Elemen
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7. TRAINING AND CERTIFICATION This
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Recommended training and certificat
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■ Level II A Level II infrared th
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The experience and education recomm
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B. Spatial Resolution • the conce
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D. Equipment Operation • Be able
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The PdM basic examination is more s
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Appendix-A The Science Of Thermogra
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Erroneous conclusions can have an e
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A.2.1 Heat and Temperature What is
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To convert changes in temperature o
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A.2.3 The Three Modes of Heat Trans
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The Fourier Conduction Law: Q/A Q =
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A.2.5 Convection Convective heat tr
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Figure A-2 Convective Heat Flow Cha
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A.2.6 Radiation Radiative heat tran
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A.2.7 Radiation Exchange at the Tar
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Charlie Chong/ Fion Zhang
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Figure A-4 Radiative Heat Flow W ε
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A.2.8 Specular and Diffuse Surfaces
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Specular or Diffuse Surfaces Diffus
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Specular and Diffuse Surfaces Confu
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Specular reflection is the mirror-l
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Reflections off Specular and Diffus
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The thermogram of the outside surfa
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Steady-state conduction Steady stat
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A.3 The Basic Physics of Infrared R
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A.3.1 Some Historical Background Th
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A.3.3 The Target Surface The chart
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Figure A-6 shows the distribution o
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Charlie Chong/ Fion Zhang
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Two physical laws define the radian
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According to (2), the wavelength at
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Figure A-7 Spectral Distribution of
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Figure A-8 shows that the instrumen
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If the emissivity of a gray body is
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Under certain conditions, an error
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EXAM score! Non-graybody (colored b
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Figure A-10 illustrates the spectra
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Figure A-10 Infrared Transmission o
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Figure A-11 Infrared Spectral Trans
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Figure A-11 shows transmission curv
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EXAM score! Glass is opaque λ > 5
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Figure A-12 Characteristics of IR T
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The characteristics of the window m
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IR Lenses - LWIR Len Charlie Chong/
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IR Lenses - Fresnel Len Charlie Cho
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Figure A-13 Components of an Infrar
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Infrared optics are available in tw
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All infrared detector-transducers e
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Figure A-14 Typical Infrared Radiat
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Germanium Len Charlie Chong/ Fion Z
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Thermopile Detector Charlie Chong/
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The IR Detectors Infrared detectors
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Figure A-15 Spectral Sensitivity of
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The Mercury- Cadmium-telluride (Hgc
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The Mercury- Cadmium-Telluride (HgC
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Point-sensing instruments for measu
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A.3.6.1 Line Scanning The purpose o
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A.3.6.2 Two-Dimensional Scanning Th
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Opto-mechanical Scanner A typical c
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Electronic scanning Electronic scan
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Figure A-18 Schematic of a Typical
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Applications for infrared FPAs incl
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Staring Charlie Chong/ Fion Zhang
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A.4.1 Point-Sensing Instruments For
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Temperature sensitivity is also cal
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EXAM score! thermal resolution (≠
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NETD - Noise Equivalent Temperature
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Figure A-19 Instrument Speed of Res
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Figure A-20 Fields of View of Infra
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Figure A-20 Fields of View of Infra
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The output requirements are totally
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Spectrally selective instruments em
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Figure A-21 Spectral Filtering for
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Figure A-22 shows a similar solutio
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A.4.2 Scanners and Imagers.Qualitat
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• Total field of view (TFOV): the
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Despite some manufacturers’ claim
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A.4.3.1 Temperature Sensitivity, Mi
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Figure A-23 Test Setup for MRTD Mea
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Page 201 and 202: ■ A standard 4 bar (slit) resolut
Page 203 and 204: Both MRTD and MTF are functions of
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Page 207 and 208: IFOVmeas: The slit width at which t
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Page 215 and 216: A.4.3.3 Speed of Response and Frame
Page 217 and 218: A.4.4 Thermal Imaging Software In o
Page 219 and 220: The newest field-portable instrumen
Page 221 and 222: Appendix B Measuring Emissivity, Re
Page 223 and 224: Figure B-1 Target Radiosity Charlie
Page 225 and 226: The reference emitter technique wor
Page 227 and 228: 1. Apply the reference emitter (E)
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Page 231 and 232: Figure B-3 Using the Reflective Emi
Page 233 and 234: Figure B-4 Using the Transmittance
Page 235 and 236: Appendix C Quick Reference Charts A
Page 237 and 238: MTF Determination Using An Ir Image
Page 239 and 240: Measuring And Setting Effective Emi
Page 241 and 242: Classification Of Faults (Guideline
Page 245 and 246: Reading: Four Emissivity: Understan
Page 247 and 248: Figure 1 shows a typical three-phas
Page 249: Figure IR1: Corresponding infrared
Page 253 and 254: The thermal nature of materials. Ma
Page 255 and 256: So in plain English, when the therm
Page 257 and 258: Figure 2: Stainless steel block. (a
Page 259 and 260: Observed with our thermal imager (w
Page 261 and 262: Can you see my eye glasses in the i
Page 263 and 264: How can the thermal imager’s read
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Page 267 and 268: In this experiment we see that the
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Page 271 and 272: Using a narrow band filter to measu
Page 273 and 274: Emissivity, the variable’s variab
Page 275 and 276: Emissivity and electrical equipment
Page 277 and 278: In manufacturing processes, steel o
Page 279 and 280: In this case, we have another power
Page 281 and 282: Figure IR1: Corresponding infrared
Page 283 and 284: Figure 7: Measuring the loads on a
Page 285 and 286: Summary Predictive maintenance PDM
Page 287 and 288: It is much like most endeavors in l
Page 289 and 290: Good Luck Charlie Chong/ Fion Zhang
Page 291: Charlie https://www.yumpu.com/en/br
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