1 / 12

ME 322: Instrumentation Lecture 10

ME 322: Instrumentation Lecture 10. February 10, 2014 Professor Miles Greiner. Announcements/Reminders. HW 3 due now (use ME 322 ID number!) HW 4 due Friday , HW 5 Due Wednesday 2/19/14 Review 2/19, Midterm Friday 2/21/14 This week: Lab 4 Strain Gage Installation

hung
Télécharger la présentation

ME 322: Instrumentation Lecture 10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ME 322: InstrumentationLecture 10 February 10, 2014 Professor Miles Greiner

  2. Announcements/Reminders • HW 3 due now (use ME 322 ID number!) • HW 4 due Friday, HW 5 Due Wednesday 2/19/14 • Review 2/19, Midterm Friday 2/21/14 • This week: Lab 4 Strain Gage Installation • Everyone must wear safety glasses

  3. UNR General Undergraduate Research Award • Apply for up to $1,500 to perform 2014-5 academic-year-projects in close collaboration with a faculty mentor • Application Deadline: April 14th, 2014 • http://environment.unr.edu/undergraduateresearch/opportunities/gura.html • I am interested in working with students who do very well in this class • Opportunities in Heat Transfer applied to Geothermal Power Plants and Nuclear Packaging

  4. Last Lecture • Propagation of Uncertainty in calculations • R = fn(x1, x2, x3, …, xn), • Likely Uncertainty in Power Product calculations • is

  5. Lab 5 Measurement of Elastic Modulus of Steel or Aluminum Beams • Find slope a of micro-strain reading meR versus end mass m • , where and a = slope • Find uncertainty wE • Power Product? (Yes or no?) • Fill in blank • Need to find best-estimate and 95%-confidence-level uncertainties of all 5 inputs

  6. Strain Gage Factor Uncertainty • In L5PP, manufacturer states • S = 2.075 ± 0.5% (pS not given) • In Lab 5, the values of and wS may be different! • In L5PP and Lab 5, assumepS = 68% (1s) • So assume the 95%-confidence-level uncertainty is twice the manufacturer stated uncertainty • S = 2.075 ± 1% (95%) • So (95%)

  7. Distance between Gage to Mass Centers, L • Measure using a ruler • In L5PP, ruler’s smallest increment is 1/16 inch • Uncertainty is 1/32 inch (half smallest increment) • Lab 5 – depends on the ruler you are issued • may be different • Assume the confidence-level for this uncertainty is 99.7% (3s) • The uncertainty with a 68% (1s) confidence level • (1/3)(1/32) inch • The uncertainty with a 95% (2s) confidence level • (2/3)(1/32) = 1/48 inch

  8. Beam Thickness T and Width W • Each are measured multiple times using different instruments • Use sample mean for the best value, • Use sample standard deviations and for the 68%-confidence-level uncertainty • The 95%-confidence-level uncertainties are • = 2 • = 2

  9. Uncertainty of the Slope, a • Fit data to yFit = ax + b using least-squares method • Uncertainty in a and b increases with standard error of the estimate (scatter of date from line)

  10. Uncertainty of Slope and Intercept • = (68%) • = (68%) • Not in the textbook • wa= ?sa (95%)

  11. Lab 5 Sample Calculations • http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Labs/Lab%2005%20Elastic%20Modulus/Lab%20Index.htm • Slope uncertainty calculation, sa • 95%-confidence-level uncertainties for each input • Relative contribution to the uncertainty in the result from the uncertainty in each input • Comparison of a result to reference value • Reference citation format

More Related