The essential purpose and basic function of all branches of engineering is design. Design begins with the recognition of a need and the conception of an idea to meet that need. One may then proceed to design equipment and processes of all varieties to meet the required needs. Testing and experimental design are now considered a necessary design step integrated into other | CHAPTER 3 MEASUREMENT AND INFERENCE Jerry Lee Hall . . Professor of Mechanical Engineering Iowa State University Ames Iowa THE MEASUREMENT PROBLEM DEFINITION OF MEASUREMENT STANDARDS OF MEASUREMENT I THE MEASURING SYSTEM I CALIBRATION DESIGN OF THE MEASURING SYSTEM I SELECTED MEASURING-SYSTEM COMPONENTS AND EXAMPLES SOURCES OF ERROR IN MEASUREMENTS ANALYSIS OF DATA CONFIDENCE LIMITS PROPAGATION OF ERROR OR UNCERTAINTY REFERENCES ADDITIONAL REFERENCES THE MEASUREMENT PROBLEM The essential purpose and basic function of all branches of engineering is design. Design begins with the recognition of a need and the conception of an idea to meet that need. One may then proceed to design equipment and processes of all varieties to meet the required needs. Testing and experimental design are now considered a necessary design step integrated into other rational procedures. Experimentation is often the only practical way of accomplishing some design tasks and this requires measurement as a source of important and necessary information. To measure any quantity of interest information or energy must be transferred from the source of that quantity to a sensing device. The transfer of information can be accomplished only by the corresponding transfer of energy. Before a sensing device or transducer can detect the signal of interest energy must be transferred to it from the signal source. Because energy is drawn from the source the very act of measurement alters the quantity to be determined. In order to accomplish a measurement successfully one must minimize the energy drawn from the source or the measurement will have little meaning. The converse of this notion is that without energy transfer no measurement can be obtained. The objective of any measurement is to obtain the most representative value x for the item measured along with a determination of its uncertainty
