1: Making Measurement Connections

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1. Why conduct experiments?

   Exercise \(\PageIndex{1}\)

   Students suggest their own reasons to conduct experiments:

   Answer

   • Test
   • Evaluate
   • Explore
   • Confirm quality
   • Discover

2. Why here in conjunction with Capstone project? Why as Junior/Senior in engineering curriculum?

3. How should process of experiment be sequenced? Many questions in each phase
   1. 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?
   2. 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 presence of sensor affect the physical principle?
   3. 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?
   4. 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?
   5. Analyze results
      • What analytical equations characterize the results?
      • How do the statistical approaches impact the confidence in 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 method of rejection reported?
      • If a hypothesis is proposed before experimentation, then does result confirm or reject hypothesis?
   6. Report (written and verbal)
      • What audience will review the experiment?
      • What level of detail is necessary for each section to:
        1. demonstrate learning outcome?
        2. prove capability of sensing device?
        3. repeat experiment for non-expert?
        4. convince decision-maker of next steps?
      • What are the proper numbers, units, and uncertainty expressions?
      • How are you organizing the content to tell story effectively?
      • Will it be reviewed in static written form or dynamic oral presentation?

Answers from any question can iteratively update prior ones

4. Useful definitions
   1. Experimental Classification
      1. Variational - quantify functional relationship of input changes to output observations; calibrating a standard
      2. Validational - test hypothesis to validate or refute; improve existing theory
      3. Pedagogical - teach/demonstrate established concept
      4. Explorational - pursue first steps of idea/theory
   2. Carefully crafted terms
      1. Parameters - fixed values for whole experiment
      2. Variable - something that undergoes change
      3. Independent variable - term that is manipulated by the experimenter
      4. Dependent variable - physical response of some sort
      5. Measurand - only those variables directly observed by a sensor

5. General Measurement Model (Figure \& Section 6.1) [Need to build my own model here]\begin{center} \includegraphics[width=0.8\textwidth]{Figure_61.jpg}\end{center}
6. Units of measure
   1. Quantity represented by three properties
      1. Dimension (fundamental physical description)
      2. Unit (from accepted standard, i.e. SI, Imperial)
      3. Magnitude (actual numerical value)
   2. Fundamental dimensions based on system of units

1. Fundamentals used in combination to create secondary dimensions

3. How to maintain universal consistency? (systems of units)
   1. Originally based on artifacts Historical context
   2. Now scientifically repeatable
   3. 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
4. Hierarchy of standards
   1. Traceable path relating unit to standard
   2. Allows trading of commodities with consistent magnitudes of units
   3. Calibration standard typically 1 part-per-billion
      • Thickness of 2 sheets of paper to football field
5. Convenient conversion factors
   • 25.4 mm = 1 inch
   • 1 kW = 1.34102 hP
   • 1 smoot = 1.70 meter
   • 1 sydharb = 500 gigalitres
   • 1 beard second = 1 angstrom