Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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A.3.4 The Transmitting Medium The transmission characteristics of the medium in the measurement path between the target and the instrument need to be considered in making nonontact thermal measurements. No loss of energy is encountered when measuring through a vacuum. For short path lengths, a few feet for example, most gases including the atmosphere, absorb very little energy and can be ignored (except where measurements of precision temperature values are required). As the path length increases to hundreds of feet, or as the air becomes heavy with water vapor, the absorption might become a factor. It is then necessary to consider the infrared transmission characteristics of the atmosphere. Charlie Chong/ Fion Zhang
Figure A-10 illustrates the spectral transmission characteristics of 0.3 km of ground level atmosphere (what is the object to detector distance in tabulating the chart? or this is not a factor as the transmittance is given as a ratio (%) with respect to transmittance in vacuum (Transmittance in vacuum=100%)). Two spectral intervals can be seen to have very high transmission. These are known as the 1.5 µm and the 8.14 µm atmospheric windows, and almost all infrared sensing and scanning instruments are designed to operate in one or the other of these windows. (unless) Usually, the difficulties encountered with transmitting media occur when the target is viewed by the instrument through another solid object such as a glass or quartz viewing port in a process. Keywords: These are known as the 1.5 µm and the 8.14 µm atmospheric windows. 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
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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
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
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
Page 97 and 98: Under certain conditions, an error
Page 99: EXAM score! Non-graybody (colored b
Page 103 and 104: Figure A-10 Infrared Transmission o
Page 105 and 106: Figure A-11 Infrared Spectral Trans
Page 107 and 108: Figure A-11 shows transmission curv
Page 109 and 110: EXAM score! Glass is opaque λ > 5
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
Page 123 and 124: All infrared detector-transducers e
Page 125 and 126: Figure A-14 Typical Infrared Radiat
Page 127 and 128: Germanium Len Charlie Chong/ Fion Z
Page 129 and 130: Thermopile Detector Charlie Chong/
Page 139 and 140: The IR Detectors Infrared detectors
Page 141 and 142: Figure A-15 Spectral Sensitivity of
Page 143 and 144: The Mercury- Cadmium-telluride (Hgc
Page 145 and 146: 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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