Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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A.3.2 Non-Contact Thermal Measurements Infrared non-contact thermal sensing instruments are classified as infrared radiation thermometers by the American Society of Testing and Materials (ASTM), even though they don’t always read out in temperatures. The laws of physics allow for the conversion of infrared radiation measurements to temperature measurements. This is done by first measuring the self-emitted radiation in the infrared portion of the electromagnetic spectrum of target surfaces, and then converting these measurements to electrical signals. In making these measurements, three sets of characteristics need to be considered: • The target surface • The transmitting medium between the target and the instrument • The measuring instrument Charlie Chong/ Fion Zhang
A.3.3 The Target Surface The chart of the electromagnetic spectrum (Figure A-3) indicates that the infrared portion of the spectrum lies adjacent to the visible. Every target surface above absolute zero (0 Kelvins or -273° Centigrade) radiates energy in the infrared. The hotter the target, the more radiant energy is emitted. When targets are hot enough, they radiate or glow in the visible part of the spectrum as well ( and beyond that, again becoming invisible again, example UV & ɣ ray) . As they cool, the eye becomes no longer able to see the emitted radiation and the targets appear to not glow at all. Infrared sensors are employed here to measure the radiation in the infrared, which can be related to target surface temperature. The visible spectrum extends from energy wavelengths of 0.4 µm for violet light to about 0.75 µm for red light. (µ or µm stands for micrometers or microns. A micron is one-millionth of a meter and is the measurement unit for radiant energy wavelength.) For practical purposes of temperature measurement, the infrared spectrum extends from 0.75 µm to about 20 µm. Charlie Chong/ Fion Zhang
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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
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
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Page 39 and 40: Appendix-A The Science Of Thermogra
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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
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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
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Page 87 and 88: Two physical laws define the radian
Page 89 and 90: According to (2), the wavelength at
Page 91 and 92: Figure A-7 Spectral Distribution of
Page 93 and 94: Figure A-8 shows that the instrumen
Page 95 and 96: If the emissivity of a gray body is
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Page 101 and 102: Figure A-10 illustrates the spectra
Page 103 and 104: Figure A-10 Infrared Transmission o
Page 105 and 106: Figure A-11 Infrared Spectral Trans
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Page 111 and 112: Figure A-12 Characteristics of IR T
Page 113 and 114: The characteristics of the window m
Page 115 and 116: IR Lenses - LWIR Len Charlie Chong/
Page 117 and 118: IR Lenses - Fresnel Len Charlie Cho
Page 119 and 120: Figure A-13 Components of an Infrar
Page 121 and 122: Infrared optics are available in tw
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Page 125 and 126: Figure A-14 Typical Infrared Radiat
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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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