ME 322 Instrumentation
Lecture 1
January 20, 2016
Dr. Miles Greiner
Professor and Interim Chair of Mechanical Engineering
Course administration, Lab 1, Probability Distribution Function, Population and sample
mean and standard deviation
Web Resources
• Course Website:
– http://wolfweb.unr.edu/homepage/greiner/teaching/
MECH322Instrumentation/
– HW, Reading and Lab assignment and handouts
– Lecture Topics, Resources and Notes
• Use WebCampus to find
– ME322 Student ID number
• Use this instead of name on homework so I can hand it back
in class (don’t use it for Labs or Exams)
– Grades
– HW Solutions
– Upload Labs
Syllabus
• http://wolfweb.unr.edu/homepage/greiner/teaching
/MECH322Instrumentation/Syllabus/Syllabus.pdf
• Grading
• Some extra credit assignments will be
available (~4% of grade)
• Normal written midterms (dates)
• Lab Practicum Final
• Courtesies
Overload Section 1002
• Added to meet needs of 10 student
• Meet in OB 102 for every lecture
– Meet in OB 101 for Midterms 1 and 2
• Sorry for this in convenience, but you must
– Drop lab section 1201
– Enroll in
• Section 1202: Tu 4:00PM - 6:45PM
• Section 1203: We 5:00PM - 7:45PM
• Section 1205: Th 4:00PM - 6:45PM
Labs
• If you want to move into any other lab you
must find someone to trade with, and both
must email Marissa Tsugawa
– tsugawam@nevada.unr.edu
• This week only
– Do not meet in PE 2
– Do Lab 1 Measure Area of UNR Quad on your
own
– http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instru
mentation/Labs/Lab%2001%20and%2002%20Quad%20Measurement
%20and%20Analysis/Lab%201.htm
– This is unusual, all other required labs are done in PE 2
Lab 1: Measure UNR Quad Area
• How much money should a landscaper budget to
cover the UNR Quad?
• 1 lbm of grass seed covers 200 ft2 and costs $3.49
• Must quickly estimate quad area. How?
• Turn in two parts:
– Upload raw results to the ME 322 course information
section of WebCampus by noon tomorrow (survey
closes at that time). Or use new Survey form.
– Turn in paper handout in class on Friday
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 stride length F will be
“correlated” with student height H?
• What does correlated mean?
• Count number of steps to
cover S and L.
Stride Length, F
• Measure a calibration course distance, DC
– Measuring Tape
– Quarter mile track (1320 ft)
– other
• Count number of strides to traverse 3 to 4 times.
–
• Report your height (H) in decimal feet.
– Not feet and inches
Determine S and L
• Walk around the quad 2 times.
– 4 measures of NSi and NLi
•
• Estimate (guess) Uncertainty
–
– Anything reasonable is ok. What is uncertainty?
• Estimate (guess) Certainty Level
– i.e. 5%, 50%, 90%...
– What is certainty level?
Calculate Area and its Uncertainty
• Area
• How would you calculate
?
• If you get A = 1,134,524.534 ± 40,502.345 ft2
• Then write A = 1,130,000 ± 40,000 ft2 (why?)
Best Estimate and Uncertainty of Cost, C
• How much money should a landscaper reasonably
charge for seed to avoid loosing money or charging
too much because he/she may need to buy extra
seed to do the job (due to the error in estimating
the area)?
• Should budget be C + mWC ?
– What should m be?
Assignment
• Measure quad area
• Upload spreadsheet to WebCampus by Noon
tomorrow (or use survey format)
• Turn in paper handout on Friday.
• Both are graded
• This is the only required lab that will not be
performed in PE 2
Lab 1 Submission to WebCampus
1) Go to Course Content of ME 322 on WebCampus
2) After you collect your data, click on the “Lab 1 Data Input” link in Course Content
Lab 1 Submission to WebCampus
3) The link will open a new window to this Google Form, DO NOT CLOSE WEBCAMPUS TAB
4) You need to find your
ME 322 assigned ID #
Find ME 322 Student Number
5) Return to the WebCampus Tab and go to My Grades
Notice your section # is here, make sure it is the same as what you are enrolled in on MyNevada
6) Your assigned ID # is here, please
enter this 4 digit # on the Google Form
If you do not have a student assigned ID # then you need to
talk to Dr. Greiner and Marissa Tsugawa for a section
assignment!!
Lab 1 Submission to WebCampus
7) Return to the Google Form Tab and accurately fill out rest
8) You must do this before
12pm on Thursday.
Have fun and good luck!
Questions
• Will all 154 of you get the same cost?
• Would one person get the same cost if he/she
repeated the measurement 154 times?
• If a measurement is repeated many times, would
the distribution of the results exhibit a pattern?
• Center and spread
• How can we quantify those patterns?
Cost Estimate Histogram
Cost Estimate [$]
• Define bin size
• Notice outliers (Can they be rationally eliminated?)
• Would shape (center and spread) change if many
more samples were acquired?
– What is “many?”
Probability Distribution function
• Shape for very large sample size
• Bell-shaped curve
Sample Size
• For example if we take 154 measurements.
• n = 154 (Sample size)
• n < N (Population size, can be infinite!)
• Population Mean (center)
1
𝜇=
𝑁
𝑁
𝑋𝑖
𝑖=1
Spread
• Population Standard Deviation
𝜎=
1
𝑁
𝑁
(𝑋𝑖 − 𝜇)2
𝑖=1
• Strongly affected by samples with large
deviations (Large Xi – m)
Estimate μ and σ
• How to estimate μ and σ from a sample n < N:
• Sample mean
1
𝜇≈𝑋=
𝑛
𝑛
𝑋𝑖
𝑖=1
• Sample standard deviation
𝜎≈𝑠=
1
𝑛−1
𝑛
(𝑋𝑖 − 𝑋)2
𝑖=1
• Standard Deviation is strongly affected by large deviations
(large Xi – 𝑋 )
• (n-1) increases s compared to (n) because small samples are
not likely to see large deviations
• Hint: Learn to use your calculator to find these!
What causes different length
measurements?
• A person’s 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 (i.e. 3 ft) may be different from that
calculated from the stride-length calibration (i.e. 4
ft)
– This causes consistent or systematic errors (the
measurement will always be higher or lower than the
true length)
• Blunders…