Engr201Lectureweek4

Engr201Lectureweek4 - ENGR 201 Evaluation &...

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1 10/11/2011 ENGR201 Lecture 4 Fall 2011 1 ENGR 201 Evaluation & Presentation of Experimental Data Lecture 4: Uncertainty Analysis Part 1 D. Miller, Mechanical Engineering & Mechanics C. Peters, Electrical & Computer Engineering Drexel University 11 October 2011 10/11/2011 ENGR201 Lecture 4 Fall 2011 2 Announcements 1 Coverage of Written and On-line Midterm this week reading and notes from lecture 1, 2, and 3 Homework problems for lectures 1, 2, and 3 Quizzes for lecture 1, 2 Written test Thursday 10/13/2011 at 8:00-9:00 AM in Main Auditorium (computational problems) Tables will be provided You may have 1 handwritten formula sheet On-line test from 5:00 PM Thursday 10/13 to 5:00 PM Friday 10/14 (concept questions, low computations) There is NO MAKEUP Check Bb Vista later this week for additional details and for those with special arrangements
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2 10/11/2011 ENGR201 Lecture 4 Fall 2011 3 Announcements 2 • No Quiz this week • Next week’s quiz will include both lecture 4 and Lecture 5 on Finite Statistics 10/11/2011 ENGR201 Lecture 4 Fall 2011 4 Homework and Readings for Week 4 • Reading from text: – Section 5.1, 5.2, 5.3, 5.4 and 5.5 – make sure to pay attention to examples • Problems from text: – 5.6, 5.8, 5.10
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3 10/11/2011 ENGR201 Lecture 4 Fall 2011 5 Measurement Process of assigning a value to a physical quantity Error Difference between our assigned value and the true value Uncertainty Estimate of the probable error in our measurement Errors are a property of the measurement Errors come from instruments, finite statistics, procedures Uncertainty is a property of the result Using uncertainty analysis we will identify, quantify, and combine error estimates to estimate the error in our final result Definition Review 10/11/2011 ENGR201 Lecture 4 Fall 2011 6 Purpose Estimating the ± what? as we design a measurement system Method Introduce uncertainty analysis Why? Develop a methodical approach Make critical evaluations of potential elements of the apparatus Spend your money on components that will really make a difference in reducing the uncertainty This Lecture
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4 10/11/2011 ENGR201 Lecture 4 Fall 2011 7 Repeated Measurements Width of the distribution is a measure of the random error Shifts the center of the distribution from the true value Result of the i-th measurement 10/11/2011 ENGR201 Lecture 4 Fall 2011 8 Total Error Here s what you will report as a result of your measurements We are going to work on how to estimate u x when the experiment (measurement system) is being designed Uncertainty analysis is the method to quantify the u x term %) ( ' P u x x x
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5 10/11/2011 ENGR201 Lecture 4 Fall 2011 9 Assumptions for Uncertainty Analysis Test objectives are known & process is clearly defined Known corrections to systematic error have been applied (Set the bathroom scale to zero before getting on) Systematic errors are independent (uncorrelated) of
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Engr201Lectureweek4 - ENGR 201 Evaluation &...

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