1: Making Measurement Connections
- Page ID
- 121246
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Willingness to ask questions (often repeatedly) to increase knowledge and understanding
- Why conduct experiments?
Students suggest their own reasons to conduct experiments:
- Answer
-
- Test
- Evaluate
- Explore
- Confirm quality
- Discover
- Why here in conjunction with Capstone project? Why as a junior or senior in engineering curriculum?
Students indicate connectivity to their current status
- Answer
-
- Sufficient foundation
- Confirmation of knowledge
- Preliminary project management
- Practice communication
- How should the process of experiment be sequenced? There are many questions in each phase:
- Planning
- Does variation alone create an experiment (i.e., changing parameters in simulation)?
- What outcomes will make for a successful experiment (regardless of data collected)?
- Should the approach include redundancy, significant precision, testing outside nominal conditions, etc.?
- Identifying system components
- What is the fundamental principle and how is it observable?
- Can the sensors reach the experimental region? AND survive the chemical/thermal/vibrational/structural environment?
- How will the signals reach the signal conditioner to display/record digital values?
- How will the presence of sensors affect the physical principle?
- Assessing performance
- What is the correlation of the independent variable to the dependent outcome and measurand?
- To what standard is the device calibrated?
- Is uncertainty based on component, combination, and/or statistics?
- Setting signal sampling
- Is the signal voltage, current, displacement, luminosity?
- What makes for a sufficient data set? Consider both individual trials as well as overall system.
- What sampling rate has sufficient accuracy without excessive storage requirements?
- How does the combination of frequencies (input, output, sampling) influence data?
- Analyze results
- What analytical equations characterize the results?
- How do the statistical approaches impact the confidence in the reported result?
- Does the trend of input-to-output correlate based on the functional relationship?
- What is the comparison with theory and/or other experiments?
- Is uncertainty constant throughout or measurement dependent?
- What are criteria for rejecting spurious data? Is the method of rejection reported?
- If a hypothesis is proposed before experimentation, does the result confirm or reject the hypothesis?
- Report (written and verbal)
- What audience will review the experiment?
- What level of detail is necessary for each section to:
- demonstrate the learning outcome?
- prove capability of the sensing device?
- repeat experiment for the non-expert?
- convince decision-maker of next steps?
- What are the proper numbers, units, and uncertainty expressions?
- How are you organizing the content to tell the story effectively?
- Will it be reviewed in a static written form or in a dynamic oral presentation?
- Planning
Answers from any question can iteratively update prior ones.
- Useful definitions
- Experimental Classification
- Variational - quantify functional relationship of input changes to output observations; calibrating a standard
- Validational - test hypothesis to validate or refute; improve existing theory
- Pedagogical - teach/demonstrate established concept
- Explorational - pursue first steps of idea/theory
- Carefully crafted terms
- Parameters - fixed values for whole experiment
- Variable - something that undergoes change
- Independent variable - term that is manipulated by the experimenter
- Dependent variable - physical response of some sort
- Measurand - only those variables directly observed by a sensor
- Experimental Classification
- General Measurement Model
Describe the use of the Extech HD350 Pitot Probe Anemometer in context of the General Measurement Model
- Answer
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Physical environment is the smaller cross section area of the wind tunnel (as compared to a large inlet area).
Numerous independent variables could be modified:
- Wind tunnel speed setting
- Spatial location of the probe
- Shape or position of upstream object deflecting air flow
A pitot probe is mounted within the test section through a small opening.
Black and white tubes connect the stagnation and static pressure ports to the handheld transducer; sometimes may be wires for electrical-based sensor.
Pressure differences converted by transducer to a numerical value.
Options for signal conditioning:
- Select units: meters per second, miles per hour, knots, etc.
- Volume flow rate: input cross-sectional area
- Sampling rate: real-time digital update, moving average of N data points
Numerical readout can be stored in handwritten notebook or digital data acquisition file.
- Units of measure
- Quantity is represented by three properties
- Dimension (fundamental physical description)
- Unit (from accepted standard, i.e. SI, Imperial)
- Magnitude (actual numerical value)
- Fundamental dimensions are based on system of units
- Quantity is represented by three properties
| Order | Name | Representation | Typical Units |
| 1. | Mass | [M] | kg, lbm |
| 2. | Length | [L] | meters, feet, miles |
| 3. | Time | [T] | seconds, days |
| 4. | Temperature | [\(\mathcal{T}\)] | Kelvin, Rankine |
| 5. | Current | [I] | Ampere |
| 6. | Light | [C] | candela, lumen |
| 7. | Matter | [n] | mol |
- Fundamentals are used in combination to create secondary dimensions (e.g., torque is equivalent to mass x length2 x time-2).
- How to maintain universal consistency? (systems of units)
- Originally based on artifacts Historical context
- Now scientifically repeatable
- Standards
- Length: meter - distance light travels in vacuum in \(\frac{1}{299,792,258}\) seconds
- Temperature: Kelvin - \(\frac{1}{273.16}\) of triple point of water
- Mass: WAS an artifact The kg is dead
- Time: second - 9,912,631,700 cycles of Cesium radiation
- Hierarchy of standards
- Traceable path relating unit to standard
- Allows trading of commodities with consistent magnitudes of units
- Calibration standard is typically 1 part-per-billion
- Thickness of 2 sheets of paper to a football field
- Convenient or unique conversion factors
- 25.4 mm = 1 inch
- 1 kW = 1.34102 hP
- 5,280 feet = 1 mile
- 1 smoot = 1.70 meter
- 1 sydharb = 500 gigalitres
- 1 beard second = 1 angstrom