Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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A.1 Introduction This appendix is presented as a reference guide to provide the practical thermographer with an understanding of the science behind the measurements. It is intended as an aid in performing and understanding non-contact thermal and thermographic measurements using infrared sensing equipment. The deployment and operation of infrared sensing instruments was, at one time, cumbersome and difficult. Thermographers were often required to perform on-the-spot calculations in order to reduce their measurement data and determine actual temperature values; this is no longer so. Modern instruments are light in weight, portable, and rugged. Menu-driven on-board software now makes it relatively simple to operate equipment and to gather data directly in terms of target temperature. Because of this very ease of operation, it is also relatively simple to misinterpret the results so easily and quickly obtained. Charlie Chong/ Fion Zhang
Erroneous conclusions can have an extremely negative effect on the measurements program and on the credibility of the thermographer. A solid understanding of the basis on which thermographic measurements are made will go a long way toward minimizing operator error and ensuring the success of the thermographic program. The subject matter in this appendix begins with a discussion of heat transfer and how radiative heat transfer is the basis for infrared thermography. The basic physics of infrared radiation and how it applies to instrument performance is explained. Finally, the performance parameters of infrared point-sensing and imaging instruments are discussed, including how to select, calibrate, and evaluate the performance of the instrument that is best suited to your application. Charlie Chong/ Fion Zhang
Page 1 and 2: Infrared Thermal Testing Reading VI
Page 3 and 4: 6.1 Basic Elements An in-house prog
Page 5 and 6: 6.1.4 Responsibilities This section
Page 7 and 8: IR Viewing Window - Opaque Polymer
Page 9 and 10: 6.1.8 Acceptance Criteria All surve
Page 11 and 12: 6.1.9 Reporting Criteria A rigid pr
Page 13 and 14: 6.1.10 Qualification of Personnel P
Page 15 and 16: EPRI Licensed Material Basic Elemen
Page 25 and 26: 7. TRAINING AND CERTIFICATION This
Page 27 and 28: Recommended training and certificat
Page 29 and 30: ■ Level II A Level II infrared th
Page 31 and 32: The experience and education recomm
Page 33 and 34: B. Spatial Resolution • the conce
Page 35 and 36: D. Equipment Operation • Be able
Page 37 and 38: The PdM basic examination is more s
Page 39: Appendix-A The Science Of Thermogra
Page 43 and 44: A.2.1 Heat and Temperature What is
Page 45 and 46: To convert changes in temperature o
Page 47 and 48: A.2.3 The Three Modes of Heat Trans
Page 49 and 50: The Fourier Conduction Law: Q/A Q =
Page 51 and 52: A.2.5 Convection Convective heat tr
Page 53 and 54: Figure A-2 Convective Heat Flow Cha
Page 55 and 56: A.2.6 Radiation Radiative heat tran
Page 57 and 58: A.2.7 Radiation Exchange at the Tar
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Page 61 and 62: Figure A-4 Radiative Heat Flow W ε
Page 63 and 64: A.2.8 Specular and Diffuse Surfaces
Page 65 and 66: Specular or Diffuse Surfaces Diffus
Page 67 and 68: Specular and Diffuse Surfaces Confu
Page 69 and 70: Specular reflection is the mirror-l
Page 71 and 72: Reflections off Specular and Diffus
Page 73 and 74: The thermogram of the outside surfa
Page 75 and 76: Steady-state conduction Steady stat
Page 77 and 78: A.3 The Basic Physics of Infrared R
Page 79 and 80: A.3.1 Some Historical Background Th
Page 81 and 82: A.3.3 The Target Surface The chart
Page 83 and 84: Figure A-6 shows the distribution o
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Page 87 and 88: Two physical laws define the radian
Page 89 and 90: 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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Charlie Chong/ Fion Zhang
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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
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Appendix B Measuring Emissivity, Re
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Figure B-1 Target Radiosity Charlie
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The reference emitter technique wor
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1. Apply the reference emitter (E)
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B.2.2 Reflective Emissivity Techniq
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Figure B-3 Using the Reflective Emi
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Figure B-4 Using the Transmittance
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Appendix C Quick Reference Charts A
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MTF Determination Using An Ir Image
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Measuring And Setting Effective Emi
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Classification Of Faults (Guideline
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Reading: Four Emissivity: Understan
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Figure 1 shows a typical three-phas
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Figure IR1: Corresponding infrared
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Thermal radiation and properties of
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The thermal nature of materials. Ma
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So in plain English, when the therm
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Figure 2: Stainless steel block. (a
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Observed with our thermal imager (w
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Can you see my eye glasses in the i
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How can the thermal imager’s read
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When we remove the block from the o
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In this experiment we see that the
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Charlie Chong/ Fion Zhang http://ww
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Using a narrow band filter to measu
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Emissivity, the variable’s variab
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Emissivity and electrical equipment
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In manufacturing processes, steel o
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In this case, we have another power
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Figure IR1: Corresponding infrared
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Figure 7: Measuring the loads on a
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Summary Predictive maintenance PDM
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It is much like most endeavors in l
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Good Luck Charlie Chong/ Fion Zhang
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Charlie https://www.yumpu.com/en/br
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