Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 1 Introduction to Engineering Technology Seventh Edition Robert J. Pond & Jeffery L. Rankinen Chapter 5 Measurement Systems

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 2 The Fundamental Units

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 3 The Fundamental Units Length –The meter defined by the path traveled by light in a vacuum during a specified time. Mass –Kilogram – defined by a cylinder of platinum-iridium alloy kept by the International Bureau of Weights and Measures in Paris. Only unit defined by an artifact. Time –The second is by a certain number of cycles of radiation form a cesium-133 atom

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 4 The Fundamental Units Temperature – o F, o C, o KTemperature – o F, o C, o K –Absolute Zero is the theoretical temperature where the molecules of an ideal gas cease to move and gas has no volume –-460 o F = -273 o C = 0 o K Electric CurrentElectric Current –The current that will produce a repelling force of 2 x N between 2 wires, 1 m long and 1 m apart Luminous IntensityLuminous Intensity –The candela, is established by a source emitting light radiation at 540 x Hz

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 5 The Fundamental Units Amount of SubstanceAmount of Substance –The mole contains the number of atoms in kg of carbon-12 Supplemental UnitsSupplemental Units –The radian is an arc of 57.3 o on a circle –The steradian is a solid angle of a sphere with a surface area on the sphere equal to r 2 Transfer StandardsTransfer Standards –Standards traceable to the international primary standard. A metrology laboratory uses transfer standards to calibrate measurement instruments

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 6 Conversion of Units within the English System Multiplying by the unit ratioMultiplying by the unit ratio –Ratios that equal 1 and that are used to convert between units. –12 inches/ 1 foot –3 feet/1 yard –Sometimes called conversion factors Many common conversion equivalents are list on the front cover of the Pond bookMany common conversion equivalents are list on the front cover of the Pond book

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 7 Conversion of Units within the English System

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 8 Conversion of Units within the International System Metric prefixes – should be memorizedMetric prefixes – should be memorized

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 9 Conversion of Units Between Systems

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 10 Precision of the Inch and Millimeter Scales Millimeter is smaller and more accurateMillimeter is smaller and more accurate –Since inches are larger than millimeters, a good rule of thumb is to convert inches measured to 3 decimal places to millimeters to 2 decimal place accuracy. Most calculators perform unit conversionMost calculators perform unit conversion

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 11 Interpreting a Scale Consider scale resolution to be no better than ½ of the smallest division This number is known as the doubtful digit – it may be underlined At the right, each mark is 1 (.001 in). The most accurate this scale can be is to.05 (.0005 in). That is 1.0, 1.5, 2.0, 2.5

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 12 Accuracy & Precision Accuracy – how true the measured value is Precision – the ability of an instrument to repeat a measurement

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 13 Significant Figures The number of significant figures is defined as “a number equal to the number of digits the datum contains, with zeros merely holding a decimal place not counted.” No quantity determined by multiplication or division can be more accurate or exact than the numbers used to generate it. When adding or subtracting, record the result to the number of significant figures of the number with the least number of digits beyond the decimal point For non-decimal numbers greater than one, record the result to the last accurate number’s place value.

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 14 Rounding Rounding to the doubtful digit: –If the number to the right of the doubtful digit is greater than or equal to 5, increase the number by one (called rounding up). –If the number to the right of the doubtful digit is less than 5, do not change the number (called rounding down).

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 15 Graphing A graph is a way to present data. The method used most in the engineering technologies is the line graph. Two variables are plotted in relation to each other. X-axis is the independent variable (the variable the experimenter controls) Ex: speed. Y-axis is the dependent variable (the variable determined by the change in the independent variable) Ex: fuel usage.

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 16 Graphing Checklist 1.Label each axis with quantity and units. 2.Properly scale each axis with regularly spaced increments. 3.X-axis is the independent variable, Y-axis is the dependent variable. 4.Plot experimental points boldly. 5.A curve of best fit through the experimental data is drawn. Sometimes this is a straight line. DO NOT connect the dots. 6.Analyze the curve to see if it fits expectations. 7. Title the graph. 8.Inspect for accuracy and neatness.

Introduction to Engineering Technology, 7 th ed. Pond and Rankinen © 2009Pearson Education, Upper Saddle River, NJ All Rights Reserved. 17 Reading Graphs Interpolation – Using a graph to examine points on a line or curve between known data points. If the line is curved, then the interpolated data are estimates. Extrapolation – Estimating a curve’s fit beyond the experimental data points. A template, such as a French curve, may be needed).