Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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Discussion Subject: Are the following statement true? • Is the absolute emittance (≠ emissivity, ε) of an object constant with disregard of reflectance ρ? • Is the 1= ε + ρ + τ, a weighted ratio of three contributing factor meant for IR thermographic measurement purpose and not a physical property of the object? • What ever the reflectance be (by surface conditioning, texture, shielding, by raising the T amb to T obj etc.) , the emittance from the object is always the same as long the T obj remain the same? • Could be say that will reflectance, transmittance coupled with the object emissivity, the actual power radiating from the object is higher than the black body? Charlie Chong/ Fion Zhang
Emissivity, the variable’s variable! Back to our steel block example, let’s discuss another very significant phenomena. We will take our unpainted metal block and drill three holes part way into the body. All three holes are one-eighth of an inch in diameter. The first is one-eighth-inch deep, the second is one-fourth-inch deep, and the third is three-eighths-inch deep. Figure IR4: Thermal image of steel block with three holes. 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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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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A.4.3.2 Spot Size (FOV) , Instantan
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■ A standard 4 bar (slit) resolut
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Both MRTD and MTF are functions of
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IFOVmeas: The slit width at which t
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FPA Charlie Chong/ Fion Zhang http:
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FPA Charlie Chong/ Fion Zhang
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A.4.3.3 Speed of Response and Frame
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A.4.4 Thermal Imaging Software In o
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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
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Page 245 and 246: Reading: Four Emissivity: Understan
Page 247 and 248: Figure 1 shows a typical three-phas
Page 249 and 250: Figure IR1: Corresponding infrared
Page 251 and 252: Thermal radiation and properties of
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
Page 265 and 266: When we remove the block from the o
Page 267 and 268: In this experiment we see that the
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Page 271: Using a narrow band filter to measu
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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