10: Common Sources of Error
- Page ID
- 146192
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 10.1: Introduction
- This page emphasizes infrared thermography's importance as an inspection tool, noting potential errors beyond equipment failure. It highlights the role of Thermography Level I technicians in recognizing error sources, their effects on thermal images, and corrective measures. The chapter outlines common thermographic errors in field inspections and provides strategies for prevention.
- 10.2: Measurement vs. Indication Errors
- This page discusses thermographic errors, dividing them into measurement errors that affect temperature accuracy and indication errors that create misleading thermal patterns. Some errors can impact both categories. It emphasizes the importance of Level I technicians in detecting and documenting these limitations.
- 10.3: Emissivity-Related Errors
- This page discusses the impact of incorrect emissivity settings on thermographic accuracy, highlighting issues like material assumptions and surface conditions. It explains how these errors can lead to misleading temperature readings and stresses the importance of verifying material properties, using approved emissivity values, and documenting assumptions to ensure accurate thermographic analysis.
- 10.4: Reflection Errors
- This page examines how reflective surfaces impact infrared radiation from sources like sunlight and equipment, which can cause inaccurate temperature readings and thermal patterns. It offers strategies to reduce these errors, such as altering the viewing angle, inputting reflected apparent temperatures, and recognizing reflective sources in the scene.
- 10.5: Atmospheric and Environmental Errors
- This page discusses how environmental factors like wind, humidity, and moisture can affect infrared radiation, leading to diminished thermal contrast and temperature accuracy in inspections. It emphasizes the importance of documenting these conditions, avoiding inspections during adverse times, and adjusting inspection timing to enhance accuracy.
- 10.6: Thermal Loading and Operating Condition Errors
- This page discusses the effectiveness of thermography, emphasizing the need for adequate thermal contrast and the potential for errors under certain conditions like low electrical loads or lack of thermal stress. Such errors may result in hidden anomalies and false negatives during inspections. To mitigate these issues, it highlights the importance of verifying operating conditions, documenting usage states, and following established inspection procedures.
- 10.7: Motion and Stability Errors
- This page discusses the impact of motion during image capture on image quality, including issues like blurring and reduced spatial resolution caused by hand movement, vibrations, and environmental factors. Recommendations for mitigation include stabilizing the camera, using gimbals for drones, and capturing multiple images to enhance quality.
- 10.8: Focus, Range and Distance (FoRD) Errors
- This page explains the FoRD (Focus, Range, Distance) concept in thermography, highlighting how errors in these areas severely affect temperature measurement accuracy. It discusses the negative impact of focus errors on spatial resolution, range errors on sensitivity, and distance errors on pixel accuracy.
- 10.9: Viewing Angle Errors
- This page highlights that oblique viewing angles can reduce perceived emissivity and increase reflections, resulting in measurement errors. It advises that measurements should be taken as close to perpendicular as possible, and any angle deviations should be carefully documented to avoid misleading patterns.
- 10.10: Camera Setup and Configuration Errors
- This page highlights common data capture errors like incorrect emissivity and reflected temperature, and stresses prevention strategies. Key recommendations include using setup checklists, verifying settings prior to data capture, and documenting parameters to ensure accurate and reliable measurements.
- 10.11: Data Handling Errors
- This page addresses the negative effects of data management errors on inspections, including issues like non-radiometric images, file overwriting, inadequate naming, and metadata loss. To mitigate these risks, it stresses the necessity of following data handling protocols, performing quality checks, and keeping backups, all of which are vital for maintaining the integrity and validity of inspection data.
- 10.12: Human Factors and Procedural Errors
- This page highlights negative human factors affecting performance, such as rushing, distraction, overconfidence, and procedural non-compliance. It proposes preventive measures like checklists, situational awareness, and adherence to certification limits to improve safety and efficiency in meticulous tasks.
- 10.13: Summary
- This page provides an overview of thermography, outlining critical concepts such as emissivity, reflection, and environmental conditions to minimize errors. It highlights the significance of operational conditions and the permanence of FoRD errors. The chapter notes that while thermal tuning affects display, it doesn’t change underlying physics, and emphasizes the importance of documentation and discipline.
- 10.14: Review Questions
- This page outlines the differences between measurement errors, caused by data inaccuracies, and indication errors due to display faults. It describes FoRD errors as permanent and highlights the ineffectiveness of thermal tuning for focus or distance errors. Excessive distance impacts pixel coverage, degrading image quality. The page also provides preventive measures for Level I technicians to reduce common errors.