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ME 322 Instrumentation Lecture 1

ME 322 Instrumentation Lecture 1 . January 22, 2014 Professor Miles Greiner. Web Tools. Course Website: http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation / HW, Reading and Lab assignment and handouts Lecture Topics, Resources and Notes WebCampus

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ME 322 Instrumentation Lecture 1

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  1. ME 322 InstrumentationLecture 1 January 22, 2014 Professor Miles Greiner

  2. Web Tools • Course Website: • http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/ • HW, Reading and Lab assignment and handouts • Lecture Topics, Resources and Notes • WebCampus • ME322 Student ID number • Grades • Upload Labs

  3. Syllabus • http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Syllabus/Syllabus.pdf • Some extra credit assignments will be available (~4% of grade)

  4. Labs • Lab Section 5 • W 1-3:45 only has 10 students • Send me an e-mail (greiner@unr.edu) if you would like to move to it • This week • Do not meet in PE 113 this week • Do Lab 1 Measure Area of UNR Quad on your own • http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Labs/Lab%2001%20and%2002%20Quad%20Measurement%20and%20Analysis/Lab%201.htm

  5. Lab 1: Measure UNR Quad Area • How much money should be budgeted to cover the UNR Quad? • 1 lbm of grass seed covers 200 ft2 and costs $3.49. • Enter results in Excel template on Lab 1 website. • Upload to WebCampus by noon tomorrow.

  6. Lab 1: Measure UNR Quad Area • How to quickly measure length of • Short Side, S • Long Side, L • Measure stride length, F • One foot to the other, not back to the first foot • Do you think F will be correlated with student height H • Count number of steps to cover S & L.

  7. Stride Length (F) • Measure a calibration distance, DC • Measuring Tape • Quarter mile track (1320 ft) • other • Count the number of strides 3 to 4 times. • Report your height (H) in decimal feet. • Will F be correlated with H?

  8. Determine S and L • Walk around the quad 2 times. • 4 measures of NSi and Nli • Estimate (guess) Uncertainty • Estimate (guess) Certainty Level • i.e. 5%, 50%, 90%...

  9. Calculate Area and Error in Area • Area • How would you calculate ? • If A = 1,134,524.534 ± 40,502.345 ft2 • Then write A = 1,130,000 ± 40,000 ft2

  10. Best Estimate and Uncertainty of Cost (C) • How much money should a landscaper charge for seed to avoid loosing money because he/she need to buy extra seed to do the job? • Should budget be C + mWC ? • What should m be?

  11. Assignment • Measure quad area • Download spreadsheet template from Lab 1 site • Upload spreadsheet to WebCampus by Noon tomorrow • Turn in paper handout on Friday. • Both are graded • This is the only required lab that will not be performed in PE113

  12. Questions • Will all 90 of you get the same cost? • Would one person get the same cost if he/she repeated the measurement 90 times? • If we repeat the measurement many times would patterns emerge? • How can we quantify these patterns • Center and spread

  13. Cost Estimate Histogram • Define bin size • Notice outliers (can they be eliminated?) • Would shape (center and spread) change if more samples were acquired? Cost Estimate [$]

  14. Probability Distribution function • Shape for very large sample size

  15. Sample Size • For example if we take 90 measurements. • n = 90 (sample size) • n < N (population size, can be infinite!) • Population size N → ∞ • Population Mean (center)

  16. Spread • Population Standard Deviation • Affected by samples with large deviations (Large Xi – m)

  17. Estimate μ and σ • How to estimate μ and σ from a sample n < N: • Sample mean • Sample standard deviation • Standard Deviation is strongly affected by large deviations (large Xi– ) • (n-1) increases s because small samples are not likely to see large deviations • Hint: Learn to use your calculator to find these!

  18. What causes different length measurements? • The stride length is not constant • This causes random variations of the measurement • The length determined by the same person will be different each time he/she makes the measurement • The average stride length used during the measurement may be different from that determined during stride-length determination (calibration) • This causes consistent or systematic errors (the measurement will always be higher or lower than the true length) • Blunders…

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